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Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Communications, Services, and Additional Information

Preface x

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

C H A P T E R

New and Changed Information for Segment

Routing Features

This table summarizes the new and changed feature information for the Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers , and lists where they are documented.

•

New and Changed Segment Routing Features, on page 1

New and Changed Segment Routing Features

Segment Routing Features Added or Modified in IOS XR Release 7.4.x

Feature Description

None No new features introduced.

Introduced/Changed in

Release

Not applicable

Where Documented

Not applicable

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

New and Changed Segment Routing Features

New and Changed Information for Segment Routing Features

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

C H A P T E R

About Segment Routing

This chapter introduces the concept of segment routing and provides a workflow for configuring segment routing.

•

Scope, on page 3

•

Need, on page 4

•

Benefits, on page 4

•

Workflow for Deploying Segment Routing, on page 5

Scope

Segment routing is a method of forwarding packets on the network based on the source routing paradigm.

The source chooses a path and encodes it in the packet header as an ordered list of segments. Segments are an identifier for any type of instruction. For example, topology segments identify the next hop toward a destination. Each segment is identified by the segment ID (SID) consisting of a flat unsigned 20-bit integer.

Segments

Interior gateway protocol (IGP) distributes two types of segments: prefix segments and adjacency segments.

Each router (node) and each link (adjacency) has an associated segment identifier (SID).

• A prefix SID is associated with an IP prefix. The prefix SID is manually configured from the segment routing global block (SRGB) range of labels, and is distributed by IS-IS or OSPF. The prefix segment steers the traffic along the shortest path to its destination. A node SID is a special type of prefix SID that identifies a specific node. It is configured under the loopback interface with the loopback address of the node as the prefix.

A prefix segment is a global segment, so a prefix SID is globally unique within the segment routing domain.

• An adjacency segment is identified by a label called an adjacency SID, which represents a specific adjacency, such as egress interface, to a neighboring router. The adjacency SID is distributed by IS-IS or OSPF. The adjacency segment steers the traffic to a specific adjacency.

An adjacency segment is a local segment, so the adjacency SID is locally unique relative to a specific router.

By combining prefix (node) and adjacency segment IDs in an ordered list, any path within a network can be constructed. At each hop, the top segment is used to identify the next hop. Segments are stacked in order at

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

About Segment Routing

Need the top of the packet header. When the top segment contains the identity of another node, the receiving node uses equal cost multipaths (ECMP) to move the packet to the next hop. When the identity is that of the receiving node, the node pops the top segment and performs the task required by the next segment.

Dataplane

Segment routing can be directly applied to the Multiprotocol Label Switching (MPLS) architecture with no change in the forwarding plane. A segment is encoded as an MPLS label. An ordered list of segments is encoded as a stack of labels. The segment to process is on the top of the stack. The related label is popped from the stack, after the completion of a segment.

Services

Segment Routing integrates with the rich multi-service capabilities of MPLS, including Layer 3 VPN (L3VPN),

Virtual Private Wire Service (VPWS), Virtual Private LAN Service (VPLS), and Ethernet VPN (EVPN).

Segment Routing for Traffic Engineering

Segment routing for traffic engineering (SR-TE) takes place through a between a source and destination pair.

Segment routing for traffic engineering uses the concept of source routing, where the source calculates the path and encodes it in the packet header as a segment. Each segment is an end-to-end path from the source to the destination, and instructs the routers in the provider core network to follow the specified path instead of the shortest path calculated by the IGP. The destination is unaware of the presence of the .

Need

With segment routing for traffic engineering (SR-TE), the network no longer needs to maintain a per-application and per-flow state. Instead, it simply obeys the forwarding instructions provided in the packet.

SR-TE utilizes network bandwidth more effectively than traditional MPLS-TE networks by using ECMP at every segment level. It uses a single intelligent source and relieves remaining routers from the task of calculating the required path through the network.

Benefits

• Ready for SDN : Segment routing was built for SDN and is the foundation for Application Engineered

Routing (AER). SR prepares networks for business models, where applications can direct network behavior. SR provides the right balance between distributed intelligence and centralized optimization and programming.

• Minimal configuration : Segment routing for TE requires minimal configuration on the source router.

• Load balancing : Unlike in RSVP-TE, load balancing for segment routing can take place in the presence of equal cost multiple paths (ECMPs).

• Supports Fast Reroute (FRR) : Fast reroute enables the activation of a pre-configured backup path within 50 milliseconds of path failure.

• Plug-and-Play deployment : Segment routing are interoperable with existing MPLS control and data planes and can be implemented in an existing deployment.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

About Segment Routing

Workflow for Deploying Segment Routing

Follow this workflow to deploy segment routing.

Configure the Segment Routing Global Block (SRGB)

Enable Segment Routing and Node SID for the IGP

Configure Segment Routing for BGP

Configure the SR-TE Policy

Configure TI-LFA and Microloop Avoidance

Configure the Segment Routing Mapping Server

Collect Traffic Statistics

Workflow for Deploying Segment Routing

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Workflow for Deploying Segment Routing

About Segment Routing

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

C H A P T E R

Configure Segment Routing Global Block

Local label allocation is managed by the label switching database (LSD). The Segment Routing Global Block

(SRGB) is the range of label values preserved for segment routing in the LSD.

•

About the Segment Routing Global Block, on page 7

•

Setup a Non-Default Segment Routing Global Block Range, on page 9

About the Segment Routing Global Block

The Segment Routing Global Block (SRGB) is a range of labels reserved for Segment Routing global segments.

A prefix-SID is advertised as a domain-wide unique index. The prefix-SID index points to a unique label within the SRGB range. The index is zero-based, meaning that the first index is 0. The MPLS label assigned to a prefix is derived from the Prefix-SID index plus the SRGB base. For example, considering an SRGB range of 16,000 to 23,999, a prefix 1.1.1.65/32 with prefix-SID index of 65 is assigned the label value of

16065 .

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Configure Segment Routing Global Block

About the Segment Routing Global Block

To keep the configuration simple and straightforward, we strongly recommended that you use a homogenous

SRGB (meaning, the same SRGB range across all nodes). Using a heterogenous SRGB (meaning, a different

SRGB range of the same size across nodes) is also supported but is not recommended.

Behaviors and Limitations

• The default SRGB in IOS XR has a size of 8000 starting from label value 16000. The default range is

16000 to 23,999. With this size, and assuming one loopback prefix per router, an operator can assign prefix SIDs to a network with 8000 routers.

• There are instances when you might need to define a different SRGB range. For example:

• Non-IOS XR nodes with a SRGB range that is different than the default IOS XR SRGB range.

• The default SRGB range is not large enough to accommodate all required prefix SIDs.

• A non-default SRGB can be configured following these guidelines:

• The SRGB starting value can be configured anywhere in the dynamic label range space (16,000 to

1,048,575).

• In Cisco IOS XR release earlier than 6.6.3, the SRGB can have a maximum configurable size of

262,143.

• In Cisco IOS XR release 6.6.3 and later, the SRGB can be configured to any size value that fits within the dynamic label range space.

• Allocating an SRGB label range does not mean that all the labels in this range are programmed in the forwarding table. The label range is just reserved for SR and not available for other purposes. Furthermore, a platform may limit the number of local labels that can be programmed.

• We recommend that the non-default SRGB be configured under the segment-routing global configuration mode. By default, all IGP instances and BGP use this SRGB.

• You can also configure a non-default SRGB under the IGP, but it is not recommended.

SRGB Label Conflicts

When you define a non-default SRGB range, there might be a label conflict (for example, if labels are already allocated, statically or dynamically, in the new SRGB range). The following system log message indicates a label conflict:

%ROUTING-ISIS-4-SRGB_ALLOC_FAIL : SRGB allocation failed: 'SRGB reservation not successful for [16000,80000], SRGB (16000 80000, SRGB_ALLOC_CONFIG_PENDING, 0x2)

(So far 16 attempts). Make sure label range is free'

To remove this conflict, you must reload the router to release the currently allocated labels and to allocate the new SRGB.

After the system reloads, LSD does not accept any dynamic label allocation before IS-IS/OSPF/BGP have registered with LSD. Upon IS-IS/OSPF/BGP registration, LSD allocates the requested SRGB (either the default range or the customized range).

After IS-IS/OSPF/BGP have registered and their SRGB is allocated, LSD starts serving dynamic label requests from other clients.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing Global Block

Setup a Non-Default Segment Routing Global Block Range

Note To avoid a potential router reload due to label conflicts, and assuming that the default SRGB size is large enough, we recommend that you use the default IOS XR SRGB range.

Note Allocating a non-default SRGB in the upper part of the MPLS label space increases the chance that the labels are available and a reload can be avoided.

Caution Modifying a SRGB configuration is disruptive for traffic and may require a reboot if the new SRGB is not available entirely.

Setup a Non-Default Segment Routing Global Block Range

This task explains how to configure a non-default SRGB range.

SUMMARY STEPS

configure

segment-routing global-block starting_value ending_value

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

Purpose

Enters XR Config mode.

RP/0/RP0/CPU0:router# configure

segment-routing global-block starting_value ending_value

Example:

Enter the lowest value that you want the SRGB range to include as the starting value. Enter the highest value that you want the SRGB range to include as the ending value.

RP/0/RP0/CPU0:router(config)# segment-routing global-block 16000 80000

Step 3 Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

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Configure Segment Routing Global Block

Setup a Non-Default Segment Routing Global Block Range

Command or Action Purpose

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

Use the show mpls label table [ label label-value ] command to verify the SRGB configuration:

Router# show mpls label table label 16000 detail

Table Label Owner State Rewrite

----- ------- ------------------------------- ------ -------

0 16000 ISIS(A):1 InUse No

(Lbl-blk SRGB, vers:0, (start_label=16000, size=64001)

What to do next

Configure prefix SIDs and enable segment routing.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

C H A P T E R

Configure Segment Routing for IS-IS Protocol

Integrated Intermediate System-to-Intermediate System (IS-IS), Internet Protocol Version 4 (IPv4), is a standards-based Interior Gateway Protocol (IGP). The Cisco IOS XR software implements the IP routing capabilities described in International Organization for Standardization (ISO)/International Engineering

Consortium (IEC) 10589 and RFC 1995, and adds the standard extensions for single topology and multitopology

IS-IS for IP Version 6 (IPv6).

This module provides the configuration information used to enable segment routing for IS-IS.

Note For additional information on implementing IS-IS on your Cisco NCS 6000 Series Routers, see the Implementing

IS-IS module in the Routing Configuration Guide for Cisco NCS 6000 Series Routers .

•

Enabling Segment Routing for IS-IS Protocol, on page 11

•

Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface, on page 13

•

IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability, on page 16

•

IS-IS Multi-Domain Prefix SID and Domain Stitching: Example, on page 19

Enabling Segment Routing for IS-IS Protocol

Segment routing on the IS-IS control plane supports the following:

• IPv4 and IPv6 control plane

• Level 1, level 2, and multi-level routing

• Prefix SIDs for host prefixes on loopback interfaces

• Adjacency SIDs for adjacencies

• MPLS penultimate hop popping (PHP) and explicit-null signaling

This task explains how to enable segment routing for IS-IS.

Before you begin

Your network must support the MPLS Cisco IOS XR software feature before you enable segment routing for

IS-IS on your router.

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Configure Segment Routing for IS-IS Protocol

Enabling Segment Routing for IS-IS Protocol

Note You must enter the commands in the following task list on every IS-IS router in the traffic-engineered portion of your network.

SUMMARY STEPS

configure

router isis instance-id

address-family { ipv4 | ipv6 } [ unicast ]

metric-style wide [ level { 1 | 2 }]

router-id loopback loopback interface used for prefix-sid

segment-routing mpls

exit

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

Step 3

Step 4

Step 5

Step 6

Purpose

Enters XR Config mode.

RP/0/RP0/CPU0:router# configure

router isis instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis isp

Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.

Note You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.

Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.

address-family { ipv4 | ipv6 } [ unicast ]

Example:

RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast metric-style wide [ level { 1 | 2 }]

Example:

Configures a router to generate and accept only wide link metrics in the Level 1 area.

RP/0/RP0/CPU0:router(config-isis-af)# metric-style wide level 1

router-id loopback loopback interface used for prefix-sid Configures router ID for each address-family (IPv4/IPv6).

Example:

RP/0/RP0/CPU0:router(config-isis-af)#router-id loopback0

IS-IS advertises the router ID in TLVs 134 (for IPv4 address family) and 140 (for IPv6 address family). Required when traffic engineering is used.

segment-routing mpls Segment routing is enabled by the following actions:

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface

Command or Action

Example:

RP/0/RP0/CPU0:router(config-isis-af)# segment-routing mpls

Purpose

• MPLS forwarding is enabled on all interfaces where

IS-IS is active.

• All known prefix-SIDs in the forwarding plain are programmed, with the prefix-SIDs advertised by remote routers or learned through local or remote mapping server.

• The prefix-SIDs locally configured are advertised.

Step 7

Step 8 exit

Example:

RP/0/RP0/CPU0:router(config-isis-af)# exit

RP/0/RP0/CPU0:router(config-isis)# exit

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

What to do next

Configure the prefix SID.

Configuring a Prefix-SID on the IS-IS Enabled Loopback

Interface

A prefix segment identifier (SID) is associated with an IP prefix. The prefix SID is manually configured from the segment routing global block (SRGB) range of labels. A prefix SID is configured under the loopback interface with the loopback address of the node as the prefix. The prefix segment steers the traffic along the shortest path to its destination.

A prefix SID can be a node SID or an Anycast SID. A node SID is a type of prefix SID that identifies a specific node. An Anycast SID is a type of prefix SID that identifies a set of nodes, and is configured with n-flag clear.

The set of nodes (Anycast group) is configured to advertise a shared prefix address and prefix SID. Anycast routing enables the steering of traffic toward multiple advertising nodes. Packets addressed to an Anycast address are forwarded to the topologically nearest nodes.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface

Strict-SPF SIDs are used to forward traffic strictly along the SPF path. Strict-SPF SIDs are not forwarded to

SR-TE . IS-IS advertises the SR Algorithm sub Type Length Value (TLV) (in the SR Router Capability

SubTLV) to include both algorithm 0 (SPF) and algorithm 1 (Strict-SPF). When the IS-IS area or level is

Strict-SPF TE-capable, Strict-SPF SIDs are used to build the SR-TE Strict-SPF . Strict-SPF SIDs are also used to program the backup paths for prefixes, node SIDs, and adjacency SIDs.

Note The same SRGB is used for both regular SIDs and strict-SPF SIDs.

The prefix SID is globally unique within the segment routing domain.

This task explains how to configure prefix segment identifier (SID) index or absolute value on the IS-IS enabled Loopback interface.

Before you begin

Ensure that segment routing is enabled on the corresponding address family.

SUMMARY STEPS

configure

router isis instance-id

interface Loopback instance

address-family { ipv4 | ipv6 } [ unicast ]

prefix-sid [ strict-spf ] { index SID-index | absolute SID-value } [ n-flag-clear ] [ explicit-null ]

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure

router isis instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis 1

Step 3

Purpose

Enters XR Config mode.

Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.

• You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.

Specifies the loopback interface and instance.

interface Loopback instance

Example:

RP/0/RP0/CPU0:router(config-isis)# interface

Loopback0

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

Configuring a Prefix-SID on the IS-IS Enabled Loopback Interface

Step 4

Step 5

Step 6

Command or Action address-family { ipv4 | ipv6 } [ unicast ]

Example:

The following is an example for ipv4 address family:

Purpose

Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.

RP/0/RP0/CPU0:router(config-isis-if)# address-family ipv4 unicast prefix-sid [ strict-spf ] { index SID-index | absolute

SID-value } [ n-flag-clear ] [ explicit-null ]

Configures the prefix-SID index or absolute value for the interface.

Example: Specify strict-spf to configure the prefix-SID to use the

SPF path instead of the SR-TE .

RP/0/RP0/CPU0:router(config-isis-if-af)# prefix-sid index 1001

Specify index SID-index for each node to create a prefix

SID based on the lower boundary of the SRGB + the index.

RP/0/RP0/CPU0:router(config-isis-if-af)# prefix-sid strict-spf index 101

Specify absolute SID-value for each node to create a specific prefix SID within the SRGB.

RP/0/RP0/CPU0:router(config-isis-if-af)# prefix-sid absolute 17001

By default, the n-flag is set on the prefix-SID, indicating that it is a node SID. For specific prefix-SID (for example,

Anycast prefix-SID), enter the n-flag-clear keyword.

IS-IS does not set the

N flag in the prefix-SID sub Type

Length Value (TLV).

To disable penultimate-hop-popping (PHP) and add explicit-Null label, enter explicit-null keyword. IS-IS sets the

E flag in the prefix-SID sub TLV.

Note IS-IS does not advertise separate explicit-NULL or flags for regular SIDs and strict-SPF SIDs.

The settings in the regular SID are used if the settings are different.

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

Verify the prefix-SID configuration:

RP/0/RP0/CPU0:router# show isis database verbose

IS-IS 1 (Level-2) Link State Database

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability

LSPID router.00-00

LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL

* 0x0000039b 0xfc27 1079 0/0/0

Area Address: 49.0001

NLPID: 0xcc

NLPID:

MT:

0x8e

Standard (IPv4 Unicast)

IPv6 Unicast

Hostname: router

IP Address: 10.0.0.1

0/0/0

IPv6 Address: 2001:0db8:1234::0a00:0001

Router Cap: 10.0.0.1, D:0, S:0

Segment Routing: I:1 V:1, SRGB Base: 16000 Range: 8000

SR Algorithm:

Algorithm: 0

<...>

Algorithm: 1

Metric: 0 IP-Extended 10.0.0.1/32

Prefix-SID Index: 1001, Algorithm:0 , R:0 N:1 P:0 E:0 V:0 L:0

Prefix-SID Index: 101, Algorithm:1, R:0 N:1 P:0 E:0 V:0 L:0

<...>

What to do next

Configure the SR-TE policy.

IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability

The following sub-TLVs support the advertisement of IPv4 and IPv6 prefix attribute flags and the source router ID of the router that originated a prefix advertisement, as described in RFC 7794.

• Prefix Attribute Flags

• IPv4 and IPv6 Source Router ID

Prefix Attribute Flags

The Prefix Attribute Flag sub-TLV supports the advertisement of attribute flags associated with prefix advertisements. Knowing if an advertised prefix is directly connected to the advertising router helps to determine how labels that are associated with an incoming packet should be processed.

This section describes the behavior of each flag when a prefix advertisement is learned from one level to another.

Note Prefix attributes are only added when wide metric is used.

Prefix Attribute Flags Sub-TLV Format

0 1 2 3 4 5 6 7 ...

+-+-+-+-+-+-+-+-+...

|X|R|N| ...

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Configure Segment Routing for IS-IS Protocol

IPv4 and IPv6 Source Router ID

+-+-+-+-+-+-+-+-+...

Prefix Attribute Flags Sub-TLV Fields

Field Description

X (External Prefix Flag) This flag is set if the prefix has been redistributed from another protocol. The value of the flag is preserved when the prefix is propagated to another level.

R (Re-advertisement Flag) This flag is set to 1 by the Level 1-2 router when the prefix is propagated between

IS-IS levels (from Level 1 to Level 2, or from Level 2 to Level 1).

This flag is set to 0 when the prefix is connected locally to an IS-IS-enabled interface (regardless of the level configured on the interface).

N (Node Flag) For prefixes that are propagated from another level:

Copy the N-flag from the prefix attribute sub-TLV, if present in the source level.

Copy the N-flag from the prefix-SID sub-TLV, if present in the source level.

Otherwise, set to 0.

For connected prefixes:

Set to 0 if prefix-attributes n-flag-clear is configured (see

Configuring

Prefix Attribute N-flag-clear ).

Set to 0 if n-flag-clear { n-flag-clearSID-index | n-flag-clearSID-value } n-flag-clear is configured (see

Configuring a Prefix-SID on the IS-IS Enabled

Loopback Interface

Otherwise, set to 1 when the prefix is a host prefix (/32 for IPV4, /128 for

IPv6) that is associated with a loopback address.

Note If the flag is set and the prefix length is not a host prefix, then the flag must be ignored.

IPv4 and IPv6 Source Router ID

The Source Router ID sub-TLV identifies the source of the prefix advertisement. The IPv4 and IPv6 source router ID is displayed in the output of the show isis database verbose command.

The Source Router ID sub-TLV is added when the following conditions are met:

The prefix is locally connected.

The N-flag is set to 1 (when it's a host prefix and the n-flag-clear configuration is not used).

The router ID is configured in the corresponding address family.

The source router ID is propagated between levels.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

Configuring Prefix Attribute N-flag-clear

Table 1: Source Router Sub-TLV Format

IPv4 Source Router ID

IPv6 Source Router ID

Type: 11

Length: 4

Value: IPv4 Router ID of the source of the prefix advertisement

Type: 12

Length: 16

Value: IPv6 Router ID of the source of the prefix advertisement

Configuring Prefix Attribute N-flag-clear

The N-flag is set to 1 when the prefix is a host prefix (/32 for IPV4, /128 for IPv6) that is associated with a loopback address. The advertising router can be configured to not set this flag. This task explains how to clear the N-flag.

SUMMARY STEPS

configure

router isis instance-id

interface Loopback instance

prefix-attributes n-flag-clear [ Level-1 | Level-2 ]

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure

router isis instance-id

Example:

Step 3

Step 4

Purpose

Enters XR Config mode.

RP/0/RP0/CPU0:router(config)# router isis 1

interface Loopback instance

Example:

Specifies the loopback interface.

RP/0/RP0/CPU0:router(config)# interface Loopback0 prefix-attributes n-flag-clear [ Level-1 | Level-2 ]

Example:

Clears the prefix attribute N-flag explicitly.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

IS-IS Multi-Domain Prefix SID and Domain Stitching: Example

Step 5

Command or Action

RP/0/RP0/CPU0:router(config-if)# isis prefix-attributes n-flag-clear

Use the commit or end command.

Purpose commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

Verify the prefix attribute configuration:

RP/0/RP0/CPU0:router# show isis database verbose

IS-IS 1 (Level-2) Link State Database

LSPID router.00-00

LSP Seq Num

* 0x0000039b

Area Address: 49.0001

LSP Checksum

0xfc27

LSP Holdtime

1079

ATT/P/OL

0/0/0

NLPID:

0xcc

0x8e

MT:

Hostname:

Standard (IPv4 Unicast)

IPv6 Unicast router

IP Address: 10.0.0.1

IPv6 Address: 2001:0db8:1234::0a00:0001

0/0/0

Router Cap: 10.0.0.1, D:0, S:0

Segment Routing: I:1 V:1, SRGB Base: 16000 Range: 8000

SR Algorithm:

Algorithm: 0

Algorithm: 1

<...>

Metric: 0 IP-Extended 10.0.0.1/32

Prefix-SID Index: 1001, Algorithm:0, R:1 N:0 P:1 E:0 V:0 L:0

Prefix Attribute Flags: X:0 R:1 N:0

Metric: 10 IP-Extended 10.0.0.2/32

Prefix-SID Index: 1002, Algorithm:0, R:0 N:1 P:0 E:0 V:0 L:0

Prefix Attribute Flags: X:0 R:0 N:1

Source Router ID: 10.0.0.2

<...>

IS-IS Multi-Domain Prefix SID and Domain Stitching: Example

IS-IS Multi-Domain Prefix SID and Domain Stitching allows you to configure multiple IS-IS instances on the same loopback interface for domain border nodes. You specify a loopback interface and prefix SID under multiple IS-IS instances to make the prefix and prefix SID reachable in different domains.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

Configure IS-IS Multi-Domain Prefix SID

This example uses the following topology. Node 5 and 9 are border nodes between two IS-IS domains (Domain1 and Domain2). Node 10 is configured as the Segment Routing Path Computation Element (SR-PCE).

Figure 1: Multi-Domain Topology

Configure IS-IS Multi-Domain Prefix SID

Specify a loopback interface and prefix SID under multiple IS-IS instances on each border node:

Example: Border Node 5 router isis Domain1 interface Loopback0 address-family ipv4 unicast prefix-sid absolute 16005 router isis Domain2 interface Loopback0 address-family ipv4 unicast prefix-sid absolute 16005

Example: Border Node 9 router isis Domain1 interface Loopback0 address-family ipv4 unicast prefix-sid absolute 16009 router isis Domain2 interface Loopback0 address-family ipv4 unicast prefix-sid absolute 16009

Border nodes 5 and 9 each run two IS-IS instances (Domain1 and Domain2) and advertise their Loopback0 prefix and prefix SID in both domains.

Nodes in both domains can reach the border nodes by using the same prefix and prefix SID. For example,

Node 3 and Node 22 can reach Node 5 using prefix SID 16005.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

Configure Common Router ID

Configure Common Router ID

On each border node, configure a common TE router ID under each IS-IS instance:

Example: Border Node 5 router isis Domain1 address-family ipv4 unicast router-id loopback0 router isis Domain2 address-family ipv4 unicast router-id loopback0

Example: Border Node 9 router isis Domain1 address-family ipv4 unicast router-id loopback0 router isis Domain2 address-family ipv4 unicast router-id loopback0

Distribute IS-IS Link-State Data

Configure BGP Link-state (BGP-LS) on Node 13 and Node 14 to report their local domain to Node 10:

Example: Node 13 router isis Domain1 distribute link-state instance-id instance-id

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for IS-IS Protocol

Distribute IS-IS Link-State Data

Example: Node 14 router isis Domain2 distribute link-state instance-id instance-id

Link-state ID starts from 32. One ID is required per IGP domain. Different domain IDs are essential to identify that the SR-TE TED belongs to a particular IGP domain.

Nodes 13 and 14 each reports its local domain in BGP-LS to Node 10.

Node 10 identifies the border nodes (Nodes 5 and 9) by their common advertised TE router ID, then combines

(stitches) the domains on these border nodes for end-to-end path computations.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

C H A P T E R

Configure Segment Routing for OSPF Protocol

Open Shortest Path First (OSPF) is an Interior Gateway Protocol (IGP) developed by the OSPF working group of the Internet Engineering Task Force (IETF). Designed expressly for IP networks, OSPF supports IP subnetting and tagging of externally derived routing information. OSPF also allows packet authentication and uses IP multicast when sending and receiving packets.

This module provides the configuration information to enable segment routing for OSPF.

Note For additional information on implementing OSPF on your Cisco NCS 6000 Series Routers, see the

Implementing OSPF module in the Routing Configuration Guide for Cisco NCS 6000 Series Routers .

•

Enabling Segment Routing for OSPF Protocol, on page 23

•

Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface, on page 25

Enabling Segment Routing for OSPF Protocol

Segment routing on the OSPF control plane supports the following:

• OSPFv2 control plane

• Multi-area

• IPv4 prefix SIDs for host prefixes on loopback interfaces

• Adjacency SIDs for adjacencies

• MPLS penultimate hop popping (PHP) and explicit-null signaling

This section describes how to enable segment routing MPLS and MPLS forwarding in OSPF. Segment routing can be configured at the instance, area, or interface level.

Before you begin

Your network must support the MPLS Cisco IOS XR software feature before you enable segment routing for

OSPF on your router.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for OSPF Protocol

Enabling Segment Routing for OSPF Protocol

Note You must enter the commands in the following task list on every OSPF router in the traffic-engineered portion of your network.

SUMMARY STEPS

configure

router ospf process-name

segment-routing mpls

area area

segment-routing mpls

exit

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure

router ospf process-name

Example:

Step 3

Step 4

Step 5

Step 6

Purpose

Enters XR Config mode.

Enables OSPF routing for the specified routing process and places the router in router configuration mode.

RP/0/RP0/CPU0:router(config)# router ospf 1 segment-routing mpls

Example:

Enables segment routing using the MPLS data plane on the routing process and all areas and interfaces in the routing process.

RP/0/RP0/CPU0:router(config-ospf)# segment-routing mpls

Enables segment routing fowarding on all interfaces in the routing process and installs the SIDs received by OSPF in the forwarding table.

Enters area configuration mode.

area area

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 0 segment-routing mpls

Example:

RP/0/RP0/CPU0:router(config-ospf-ar)# segment-routing mpls exit

Example:

(Optional) Enables segment routing using the MPLS data plane on the area and all interfaces in the area. Enables segment routing fowarding on all interfaces in the area and installs the SIDs received by OSPF in the forwarding table.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for OSPF Protocol

Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface

Step 7

Command or Action

RP/0/RP0/CPU0:router(config-ospf-ar)# exit

RP/0/RP0/CPU0:router(config-ospf)# exit

Use the commit or end command.

Purpose commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

What to do next

Configure the prefix SID.

Configuring a Prefix-SID on the OSPF-Enabled Loopback

Interface

The prefix SID is globally unique within the segment routing domain.

This task describes how to configure prefix segment identifier (SID) index or absolute value on the

OSPF-enabled Loopback interface.

Before you begin

Ensure that segment routing is enabled on an instance, area, or interface.

SUMMARY STEPS

configure

router ospf process-name

area value

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for OSPF Protocol

Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface

interface Loopback interface-instance

prefix-sid [ strict-spf ] { index SID-index | absolute SID-value } [ n-flag-clear ] [ explicit-null ]

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure

router ospf process-name

Example:

Step 3

Step 4

Step 5

Step 6

RP/0/RP0/CPU0:router(config)# router ospf 1

area value

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 0

interface Loopback interface-instance

Example:

Purpose

Enters XR Config mode.

Enables OSPF routing for the specified routing process, and places the router in router configuration mode.

Enters area configuration mode.

Specifies the loopback interface and instance.

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

Loopback0 passive prefix-sid

SID-value

Example:

[ strict-spf

} [

] { index SID-index n-flag-clear ] [ explicit-null

] absolute

RP/0/RP0/CPU0:router(config-ospf-ar)# prefix-sid index 1001

RP/0/RP0/CPU0:router(config-ospf-ar)# prefix-sid absolute 17001

Configures the prefix-SID index or absolute value for the interface.

Specify strict-spf to configure the prefix-SID to use the

SPF path instead of the SR-TE tunnel.

Specify index SID-index for each node to create a prefix

SID based on the lower boundary of the SRGB + the index.

Specify absolute SID-value for each node to create a specific prefix SID within the SRGB.

By default, the n-flag is set on the prefix-SID, indicating that it is a node SID. For specific prefix-SID (for example,

Anycast prefix-SID), enter the n-flag-clear keyword.

OSPF does not set the

N flag in the prefix-SID sub Type

Length Value (TLV).

To disable penultimate-hop-popping (PHP) and add an explicit-Null label, enter the explicit-null keyword. OSPF sets the

E flag in the prefix-SID sub TLV.

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for OSPF Protocol

Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface

Command or Action Purpose end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

Verify the prefix-SID configuration:

RP/0/RP0/CPU0:router# show ospf database opaque-area 7.0.0.1 self-originate

OSPF Router with ID (10.0.0.1) (Process ID 1)

Type-10 Opaque Link Area Link States (Area 0)

<...>

Extended Prefix TLV: Length: 20

Route-type: 1

AF : 0

Flags

Prefix

: 0x40

: 10.0.0.1/32

SID sub-TLV: Length: 8

Flags : 0x0

MTID

Algo

: 0

SID Index : 1001

What to do next

Configure SR-TE Policies

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configuring a Prefix-SID on the OSPF-Enabled Loopback Interface

Configure Segment Routing for OSPF Protocol

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

C H A P T E R

Configure Segment Routing for BGP

Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to create loop-free inter-domain routing between autonomous systems. An autonomous system is a set of routers under a single technical administration. Routers in an autonomous system can use multiple Interior Gateway Protocols (IGPs) to exchange routing information inside the autonomous system and an EGP to route packets outside the autonomous system.

This module provides the configuration information used to enable Segment Routing for BGP.

Note For additional information on implementing BGP on your Cisco NCS 6000 Series Routers, see the Implementing

BGP module in the Routing Configuration Guide for Cisco NCS 6000 Series Routers .

•

Segment Routing for BGP, on page 29

•

Configure BGP Prefix Segment Identifiers, on page 30

•

Segment Routing Egress Peer Engineering, on page 31

•

Configure BGP Link-State, on page 32

•

Example: Configuring SR-EPE and BGP-LS, on page 34

Segment Routing for BGP

In a traditional BGP-based data center (DC) fabric, packets are forwarded hop-by-hop to each node in the autonomous system. Traffic is directed only along the external BGP (eBGP) multipath ECMP. No traffic engineering is possible.

In an MPLS-based DC fabric, the eBGP sessions between the nodes exchange BGP labeled unicast (BGP-LU) network layer reachability information (NLRI). An MPLS-based DC fabric allows any leaf (top-of-rack or border router) in the fabric to communicate with any other leaf using a single label, which results in higher packet forwarding performance and lower encapsulation overhead than traditional BGP-based DC fabric.

However, since each label value might be different for each hop, an MPLS-based DC fabric is more difficult to troubleshoot and more complex to configure.

BGP has been extended to carry segment routing prefix-SID index. BGP-LU helps each node learn BGP prefix SIDs of other leaf nodes and can use ECMP between source and destination. Segment routing for BGP simplifies the configuration, operation, and troubleshooting of the fabric. With segment routing for BGP, you can enable traffic steering capabilities in the data center using a BGP prefix SID.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for BGP

Configure BGP Prefix Segment Identifiers

Configure BGP Prefix Segment Identifiers

Segments associated with a BGP prefix are known as BGP prefix SIDs. The BGP prefix SID is global within a segment routing or BGP domain. It identifies an instruction to forward the packet over the ECMP-aware best-path computed by BGP to the related prefix. The BGP prefix SID is manually configured from the segment routing global block (SRGB) range of labels.

Each BGP speaker must be configured with an SRGB using the segment-routing global-block command.

See the

About the Segment Routing Global Block

section for information about the SRGB.

Note Because the values assigned from the range have domain-wide significance, we recommend that all routers within the domain be configured with the same range of values.

To assign a BGP prefix SID, first create a routing policy using the set label-index index attribute, then associate the index to the node.

Note A routing policy with the set label-index attribute can be attached to a network configuration or redistribute configuration. Other routing policy language (RPL) configurations are possible. For more information on routing policies, refer to the "Implementing Routing Policy" chapter in the Routing Configuration Guide for

Cisco NCS 6000 Series Routers .

Example

The following example shows how to configure the SRGB, create a BGP route policy using a $SID parameter and set label-index attribute, and then associate the prefix-SID index to the node.

RP/0/RSP0/CPU0:router(config)# segment-routing global-block 16000 23999

RP/0/RSP0/CPU0:router(config)# route-policy SID($SID)

RP/0/RSP0/CPU0:router(config-rpl)# set label-index $SID

RP/0/RSP0/CPU0:router(config-rpl)# end policy

RP/0/RSP0/CPU0:router(config)# router bgp 1

RP/0/RSP0/CPU0:router(config-bgp)# bgp router-id 1.1.1.1

RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicast

RP/0/RSP0/CPU0:router(config-bgp-af)# network 1.1.1.3/32 route-policy SID(3)

RP/0/RSP0/CPU0:router(config-bgp-af)# allocate-label all

RP/0/RSP0/CPU0:router(config-bgp-af)# commit

RP/0/RSP0/CPU0:router(config-bgp-af)# end

RP/0/RSP0/CPU0:router# show bgp 1.1.1.3/32

BGP routing table entry for 1.1.1.3/32

Versions:

Process

Speaker bRIB/RIB SendTblVer

74 74

Local Label: 16003

Last Modified: Sep 29 19:52:18.155 for 00:07:22

Paths: (1 available, best #1)

Advertised to update-groups (with more than one peer):

0.2

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for BGP

Segment Routing Egress Peer Engineering

Path #1: Received by speaker 0

Advertised to update-groups (with more than one peer):

0.2

99.3.21.3 from 99.3.21.3 (1.1.1.3)

Received Label 3

Origin IGP, metric 0, localpref 100, valid, external, best, group-best

Received Path ID 0, Local Path ID 1, version 74

Origin-AS validity: not-found

Label Index: 3

Segment Routing Egress Peer Engineering

Segment routing egress peer engineering (EPE) uses a controller to instruct an ingress provider edge, or a content source (node) within the segment routing domain, to use a specific egress provider edge (node) and a specific external interface to reach a destination. BGP peer SIDs are used to express source-routed inter-domain paths.

Below are the BGP-EPE peering SID types:

• PeerNode SID—To an eBGP peer. Pops the label and forwards the traffic on any interface to the peer.

• PeerAdjacency SID—To an eBGP peer via interface. Pops the label and forwards the traffic on the related interface.

The controller learns the BGP peer SIDs and the external topology of the egress border router through BGP-LS

EPE routes. The controller can program an ingress node to steer traffic to a destination through the egress node and peer node using BGP labeled unicast (BGP-LU).

EPE functionality is only required at the EPE egress border router and the EPE controller.

Configure Segment Routing Egress Peer Engineering

This task explains how to configure segment routing EPE on the EPE egress node.

SUMMARY STEPS

router bgp as-number

neighbor ip-address

remote-as as-number

egress-engineering

DETAILED STEPS

Step 1

Command or Action

router bgp as-number

Example:

RP/0/RSP0/CPU0:router(config)# router bgp 1

Purpose

Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for BGP

Configure BGP Link-State

Step 2

Command or Action

neighbor ip-address

Example:

RP/0/RSP0/CPU0:router(config-bgp)# neighbor

192.168.1.3

Purpose

Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

Step 3

Step 4

remote-as as-number

Example:

RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as

Creates a neighbor and assigns a remote autonomous system number to it.

Configures the egress node with EPE for the eBGP peer.

egress-engineering

Example:

RP/0/RSP0/CPU0:router(config-bgp-nbr)# egress-engineering

Configure BGP Link-State

BGP Link-State (LS) is an Address Family Identifier (AFI) and Sub-address Family Identifier (SAFI) originally defined to carry interior gateway protocol (IGP) link-state information through BGP. The BGP Network Layer

Reachability Information (NLRI) encoding format for BGP-LS and a new BGP Path Attribute called the

BGP-LS attribute are defined in RFC7752 . The identifying key of each Link-State object, namely a node, link, or prefix, is encoded in the NLRI and the properties of the object are encoded in the BGP-LS attribute.

The BGP-LS Extensions for Segment Routing are documented in RFC9085 .

BGP-LS applications like an SR Path Computation Engine (SR-PCE) can learn the SR capabilities of the nodes in the topology and the mapping of SR segments to those nodes. This can enable the SR-PCE to perform path computations based on SR-TE and to steer traffic on paths different from the underlying IGP-based distributed best-path computation.

The following figure shows a typical deployment scenario. In each IGP area, one or more nodes (BGP speakers) are configured with BGP-LS. These BGP speakers form an iBGP mesh by connecting to one or more route-reflectors. This way, all BGP speakers (specifically the route-reflectors) obtain Link-State information from all IGP areas (and from other ASes from eBGP peers).

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for BGP

Configure BGP Link-State

Usage Guidelines and Limitations

• BGP-LS supports IS-IS and OSPFv2.

• The identifier field of BGP-LS (referred to as the Instance-ID) identifies the IGP routing domain where the NLRI belongs. The NLRIs representing link-state objects (nodes, links, or prefixes) from the same

IGP routing instance must use the same Instance-ID value.

• When there is only a single protocol instance in the network where BGP-LS is operational, we recommend configuring the Instance-ID value to 0 .

• Assign consistent BGP-LS Instance-ID values on all BGP-LS Producers within a given IGP domain.

• NLRIs with different Instance-ID values are considered to be from different IGP routing instances.

• Unique Instance-ID values must be assigned to routing protocol instances operating in different IGP domains. This allows the BGP-LS Consumer (for example, SR-PCE) to build an accurate segregated multi-domain topology based on the Instance-ID values, even when the topology is advertised via BGP-LS by multiple BGP-LS Producers in the network.

• If the BGP-LS Instance-ID configuration guidelines are not followed, a BGP-LS Consumer may see duplicate link-state objects for the same node, link, or prefix when there are multiple BGP-LS Producers deployed. This may also result in the BGP-LS Consumers getting an inaccurate network-wide topology.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for BGP

Example: Configuring SR-EPE and BGP-LS

Exchange Link State Information with BGP Neighbor

The following example shows how to exchange link-state information with a BGP neighbor:

Router# configure

Router(config)# router bgp 1

Router(config-bgp)# neighbor 10.0.0.2

Router(config-bgp-nbr)# remote-as 1

Router(config-bgp-nbr)# address-family link-state link-state

Router(config-bgp-nbr-af)# exit

IGP Link-State Database Distribution

A given BGP node may have connections to multiple, independent routing domains. IGP link-state database distribution into BGP-LS is supported for both OSPF and IS-IS protocols in order to distribute this information on to controllers or applications that desire to build paths spanning or including these multiple domains.

To distribute IS-IS link-state data using BGP-LS, use the distribute link-state command in router configuration mode.

Router# configure

Router(config)# router isis isp

Router(config-isis)# distribute link-state instance-id 32

To distribute OSPFv2 link-state data using BGP-LS, use the distribute link-state command in router configuration mode.

Router# configure

Router(config)# router ospf 100

Router(config-ospf)# distribute link-state instance-id 32

Example: Configuring SR-EPE and BGP-LS

In the following figure, segment routing is enabled on autonomous system AS1 with ingress node A and egress nodes B and C. In this example, we configure EPE on egress node C.

Figure 2: Topology

Step 1 Configure node C with EPE for eBGP peers D and E.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for BGP

Example: Configuring SR-EPE and BGP-LS

Step 2

Step 3

Step 4

Example:

RP/0/RSP0/CPU0:router_C(config)# router bgp 1

RP/0/RSP0/CPU0:router_C(config-bgp)# neighbor 192.168.1.3

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# remote-as 3

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# description to E

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# egress-engineering

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# address-family ipv4 unicast

RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# route-policy bgp_in in

RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# route-policy bgp_out out

RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# exit

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# exit

RP/0/RSP0/CPU0:router_C(config-bgp)# neighbor 192.168.1.2

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# remote-as 2

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# description to D

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# egress-engineering

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# address-family ipv4 unicast

RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# route-policy bgp_in in

RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# route-policy bgp_out out

RP/0/RSP0/CPU0:router_C(config-bgp-nbr-af)# exit

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# exit

Configure node C to advertise peer node SIDs to the controller using BGP-LS.

Example:

RP/0/RSP0/CPU0:router_C(config-bgp)# neighbor 172.29.50.71

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# remote-as 1

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# description to EPE_controller

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# address-family link-state link-state

RP/0/RSP0/CPU0:router_C(config-bgp-nbr)# exit

RP/0/RSP0/CPU0:router_C(config-bgp)# exit

Commit the configuration.

Example:

RP/0/RSP0/CPU0:router_C(config)# commit

Verify the configuration.

Example:

RP/0/RSP0/CPU0:router_C# show bgp egress-engineering

Egress Engineering Peer Set: 192.168.1.2/32 (10b87210)

Nexthop: 192.168.1.2

Version: 2, rn_version: 2

Flags: 0x00000002

Local ASN: 1

Remote ASN: 2

Local RID: 1.1.1.3

Remote RID: 1.1.1.4

First Hop: 192.168.1.2

NHID: 3

Label: 24002 , Refcount: 3 rpc_set: 10b9d408

Egress Engineering Peer Set: 192.168.1.3/32 (10be61d4)

Nexthop: 192.168.1.3

Version: 3, rn_version: 3

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure Segment Routing for BGP

Example: Configuring SR-EPE and BGP-LS

Flags: 0x00000002

Local ASN: 1

Remote ASN: 3

Local RID: 1.1.1.3

Remote RID: 1.1.1.5

First Hop: 192.168.1.3

NHID: 4

Label: 24003 , Refcount: 3 rpc_set: 10be6250

The output shows that node C has allocated peer SIDs for each eBGP peer.

Example:

RP/0/RSP0/CPU0:router_C# show mpls forwarding labels 24002 24003

Local Outgoing

Label Label

Prefix or ID

Outgoing

Interface

Next Hop Bytes

Switched

------ ----------- ------------------ ------------ --------------- ------------

24002 Unlabelled No ID Te0/3/0/0 192.168.1.2

24003 Unlabelled No ID Te0/1/0/0 192.168.1.3

The output shows that node C installed peer node SIDs in the Forwarding Information Base (FIB).

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure SR-TE Policies

C H A P T E R

This module provides information about segment routing for traffic engineering (SR-TE) policies, how to configure SR-TE policies, and how to steer traffic into an SR-TE policy.

•

SR-TE Policy Overview, on page 37

•

Usage Guidelines and Limitations, on page 38

•

Instantiation of an SR Policy, on page 38

•

SR-TE Policy Path Types, on page 68

•

Protocols, on page 77

•

Traffic Steering, on page 84

•

Miscellaneous, on page 95

SR-TE Policy Overview

Segment routing for traffic engineering (SR-TE) uses a “policy” to steer traffic through the network. An

SR-TE policy path is expressed as a list of segments that specifies the path, called a segment ID (SID) list.

Each segment is an end-to-end path from the source to the destination, and instructs the routers in the network to follow the specified path instead of following the shortest path calculated by the IGP. If a packet is steered into an SR-TE policy, the SID list is pushed on the packet by the head-end. The rest of the network executes the instructions embedded in the SID list.

An SR-TE policy is identified as an ordered list (head-end, color, end-point):

• Head-end – Where the SR-TE policy is instantiated

• Color – A numerical value that distinguishes between two or more policies to the same node pairs

(Head-end – End point)

• End-point – The destination of the SR-TE policy

Every SR-TE policy has a color value. Every policy between the same node pairs requires a unique color value.

An SR-TE policy uses one or more candidate paths. A candidate path is a single segment list (SID-list) or a set of weighted SID-lists (for weighted equal cost multi-path [WECMP]). A candidate path is either dynamic or explicit. See SR-TE Policy Path Types section for more information.

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Usage Guidelines and Limitations

Usage Guidelines and Limitations

Observe the following guidelines and limitations for the platform.

• GRE tunnel as primary interface for an SR policy is not supported.

• GRE tunnel as backup interface for an SR policy with TI-LFA protection is not supported.

Instantiation of an SR Policy

An SR policy is instantiated, or implemented, at the head-end router.

The following sections provide details on the SR policy instantiation methods:

•

On-Demand SR Policy – SR On-Demand Next-Hop , on page 38

•

Manually Provisioned SR Policy, on page 68

•

PCE-Initiated SR Policy, on page 68

On-Demand SR Policy – SR On-Demand Next-Hop

Segment Routing On-Demand Next Hop (SR-ODN) allows a service head-end router to automatically instantiate an SR policy to a BGP next-hop when required (on-demand). Its key benefits include:

• SLA-aware BGP service – Provides per-destination steering behaviors where a prefix, a set of prefixes, or all prefixes from a service can be associated with a desired underlay SLA. The functionality applies equally to single-domain and multi-domain networks.

• Simplicity – No prior SR Policy configuration needs to be configured and maintained. Instead, operator simply configures a small set of common intent-based optimization templates throughout the network.

• Scalability – Device resources at the head-end router are used only when required, based on service or

SLA connectivity needs.

The following example shows how SR-ODN works:

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On-Demand SR Policy – SR On-Demand Next-Hop

An egress PE (node H) advertises a BGP route for prefix T/t. This advertisement includes an SLA intent encoded with a BGP color extended community. In this example, the operator assigns color purple (example value = 100) to prefixes that should traverse the network over the delay-optimized path.

The route reflector receives the advertised route and advertises it to other PE nodes.

Ingress PEs in the network (such as node F) are pre-configured with an ODN template for color purple that provides the node with the steps to follow in case a route with the intended color appears, for example:

• Contact SR-PCE and request computation for a path toward node H that does not share any nodes with another LSP in the same disjointness group.

• At the head-end router, compute a path towards node H that minimizes cumulative delay.

In this example, the head-end router contacts the SR-PCE and requests computation for a path toward node H that minimizes cumulative delay.

After SR-PCE provides the compute path, an intent-driven SR policy is instantiated at the head-end router.

Other prefixes with the same intent (color) and destined to the same egress PE can share the same on-demand SR policy. When the last prefix associated with a given [intent, egress PE] pair is withdrawn, the on-demand SR policy is deleted, and resources are freed from the head-end router.

An on-demand SR policy is created dynamically for BGP global or VPN (service) routes. The following services are supported with SR-ODN:

• IPv4 BGP global routes

• IPv6 BGP global routes (6PE)

• VPNv4

• VPNv6 (6vPE)

• EVPN-VPWS (single-homing)

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SR-ODN Configuration Steps

SR-ODN Configuration Steps

To configure SR-ODN, complete the following configurations:

Define the SR-ODN template on the SR-TE head-end router.

(Optional) If using Segment Routing Path Computation Element (SR-PCE) for path computation: a.

Configure SR-PCE. For detailed SR-PCE configuration information, see

Configure SR-PCE, on page

120 .

Configure the head-end router as Path Computation Element Protocol (PCEP) Path Computation

Client (PCC). For detailed PCEP PCC configuration information, see

Configure the Head-End Router as PCEP PCC .

Define BGP color extended communities. Refer to the "Implementing BGP" chapter in the Routing

Configuration Guide for Cisco NCS 6000 Series Routers .

Define routing policies (using routing policy language [RPL]) to set BGP color extended communities.

Refer to the "Implementing Routing Policy" chapter in the Routing Configuration Guide for Cisco NCS

6000 Series Routers .

The following RPL attach-points for setting/matching BGP color extended communities are supported:

Note The following table shows the supported RPL match operations; however, routing policies are required primarily to set BGP color extended community. Matching based on BGP color extended communities is performed automatically by ODN's on-demand color template.

Attach Point

VRF export

VRF import

Neighbor-in

Neighbor-out

Inter-AFI export

Inter-AFI import

Default-originate

Set

–

Match

–

Apply routing policies to a service. Refer to the "Implementing Routing Policy" chapter in the Routing

Configuration Guide for Cisco NCS 6000 Series Routers .

Configure On-Demand Color Template

• Use the on-demand color color command to create an ODN template for the specified color value. The head-end router automatically follows the actions defined in the template upon arrival of BGP global or

VPN routes with a BGP color extended community that matches the color value specified in the template.

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SR-ODN Configuration Steps

The color range is from 1 to 4294967295.

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# on-demand color 10

Note Matching based on BGP color extended communities is performed automatically via ODN's on-demand color template. RPL routing policies are not required.

• Use the on-demand color color dynamic command to associate the template with on-demand SR policies with a locally computed dynamic path (by SR-TE head-end router utilizing its TE topology database) or centrally (by SR-PCE). The head-end router will first attempt to install the locally computed path; otherwise, it will use the path computed by the SR-PCE.

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# on-demand color 10 dynamic

• Use the on-demand color color dynamic pcep command to indicate that only the path computed by

SR-PCE should be associated with the on-demand SR policy. With this configuration, local path computation is not attempted; instead the head-end router will only instantiate the path computed by the

SR-PCE.

Router(config-sr-te)# on-demand color 10 dynamic pcep

Configure Dynamic Path Optimization Objectives

• Use the metric type { igp | te | latency } command to configure the metric for use in path computation.

Router(config-sr-te-color-dyn)# metric type te

• Use the metric margin { absolute value | relative percent } command to configure the On-Demand dynamic path metric margin. The range for value and percent is from 0 to 2147483647.

Router(config-sr-te-color-dyn)# metric margin absolute 5

Configure Dynamic Path Constraints

• Use the disjoint-path group-id group-id type { link | node | srlg | srlg-node } [ sub-id sub-id ] command to configure the disjoint-path constraints. The group-id and sub-id range is from 1 to 65535.

Router(config-sr-te-color-dyn)# disjoint-path group-id 775 type link

• Use the affinity { include-any | include-all | exclude-any } { name WORD } command to configure the affinity constraints.

Router(config-sr-te-color-dyn)# affinity exclude-any name CROSS

• Use the maximum-sid-depth value command to customize the maximum SID depth (MSD) constraints advertised by the router.

The default MSD value is equal to the maximum MSD supported by the platform ().

Router(config-sr-te-color)# maximum-sid-depth 5

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See

Customize MSD Value at PCC, on page 79

for information about SR-TE label imposition capabilities.

• Use the sid-algorithm algorithm-number command to configure the SR Flexible Algorithm constraints.

The algorithm-number range is from 128 to 255.

Router(config-sr-te-color-dyn)# sid-algorithm 128

Configuring SR-ODN: Examples

Configuring SR-ODN: Layer-3 Services Examples

The following examples show end-to-end configurations used in implementing SR-ODN on the head-end router.

Configuring ODN Color Templates: Example

Configure ODN color templates on routers acting as SR-TE head-end nodes. The following example shows various ODN color templates:

• color 10: minimization objective = te-metric

• color 20: minimization objective = igp-metric

• color 21: minimization objective = igp-metric; constraints = affinity

• color 22: minimization objective = te-metric; path computation at SR-PCE; constraints = affinity segment-routing traffic-eng on-demand color 10 dynamic metric type te

on-demand color 20 dynamic

metric type igp

on-demand color 21 dynamic metric

type igp

affinity exclude-any name CROSS

on-demand color 22 dynamic pcep

metric

type te

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end

affinity exclude-any name CROSS

Configuring BGP Color Extended Community Set: Example

The following example shows how to configure BGP color extended communities that are later applied to

BGP service routes via route-policies.

Note In most common scenarios, egress PE routers that advertise BGP service routes apply (set) BGP color extended communities. However, color can also be set at the ingress PE router.

extcommunity-set opaque color10-te

10 end-set

extcommunity-set opaque color20-igp

20 end-set

extcommunity-set opaque color21-igp-excl-cross

21 end-set

Configuring RPL to Set BGP Color (Layer-3 Services): Examples

The following example shows various representative RPL definitions that set BGP color community.

The examples include the set color action only. The last RPL example performs the set color action for selected destinations based on a prefix-set.

route-policy SET_COLOR_LOW_LATENCY_TE set extcommunity color color10-te pass end-policy

route-policy SET_COLOR_HI_BW set extcommunity color color20-igp pass end-policy

prefix-set sample-set

88.1.0.0/24 end-set

route-policy SET_COLOR_GLOBAL if destination in sample-set then set extcommunity color color10-te else pass endif end-policy

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Applying RPL to BGP Services (Layer-3 Services): Example

The following example shows various RPLs that set BGP color community being applied to BGP Layer-3

VPN services (VPNv4/VPNv6) and BGP global.

• The L3VPN examples show the RPL applied at the VRF export attach-point.

• The BGP global example shows the RPL applied at the BGP neighbor-out attach-point.

vrf vrf_cust1 address-family ipv4 unicast export route-policy SET_COLOR_LOW_LATENCY_TE

address-family ipv6 unicast export route-policy SET_COLOR_LOW_LATENCY_TE

vrf vrf_cust2 address-family ipv4 unicast export route-policy SET_COLOR_HI_BW

address-family ipv6 unicast export route-policy SET_COLOR_HI_BW router bgp 100 neighbor-group BR-TO-RR address-family ipv4 unicast route-policy SET_COLOR_GLOBAL out

end

Verifying BGP VRF Information

Use the show bgp vrf command to display BGP prefix information for VRF instances. The following output shows the BGP VRF table including a prefix (88.1.1.0/24) with color 10 advertised by router 1.1.1.8.

RP/0/RP0/CPU0:R4# show bgp vrf vrf_cust1

BGP VRF vrf_cust1, state: Active

BGP Route Distinguisher: 1.1.1.4:101

VRF ID: 0x60000007

BGP router identifier 1.1.1.4, local AS number 100

Non-stop routing is enabled

BGP table state: Active

Table ID: 0xe0000007 RD version: 282

BGP main routing table version 287

BGP NSR Initial initsync version 31 (Reached)

BGP NSR/ISSU Sync-Group versions 0/0

Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

Route Distinguisher: 1.1.1.4:101 (default for vrf vrf_cust1)

*> 44.1.1.0/24 40.4.101.11

0 400 {1} i

*>i55.1.1.0/24

*>i88.1.1.0/24

*>i99.1.1.0/24

1.1.1.5

1.1.1.8 C:10

1.1.1.9

100

100

100

0 500 {1} i

0 800 {1} i

0 800 {1} i

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Processed 4 prefixes, 4 paths

The following output displays the details for prefix 88.1.1.0/24. Note the presence of BGP extended color community 10, and that the prefix is associated with an SR policy with color 10 and BSID value of 24036.

RP/0/RP0/CPU0:R4# show bgp vrf vrf_cust1 88.1.1.0/24

BGP routing table entry for 88.1.1.0/24, Route Distinguisher: 1.1.1.4:101

Versions:

Process

Speaker bRIB/RIB

282

SendTblVer

282

Last Modified: May 20 09:23:34.112 for 00:06:03

Paths: (1 available, best #1)

Advertised to CE peers (in unique update groups):

40.4.101.11

Path #1: Received by speaker 0

Advertised to CE peers (in unique update groups):

40.4.101.11

800 {1}

1.1.1.8 C:10 (bsid:24036) (metric 20) from 1.1.1.55 (1.1.1.8)

Received Label 24012

Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported

Received Path ID 0, Local Path ID 1, version 273

Extended community: Color:10 RT:100:1

Originator: 1.1.1.8, Cluster list: 1.1.1.55

SR policy color 10, up, registered, bsid 24036, if-handle 0x08000024

Source AFI: VPNv4 Unicast, Source VRF: default, Source Route Distinguisher: 1.1.1.8:101

Verifying Forwarding (CEF) Table

Use the show cef vrf command to display the contents of the CEF table for the VRF instance. Note that prefix

88.1.1.0/24 points to the BSID label corresponding to an SR policy. Other non-colored prefixes, such as

55.1.1.0/24, point to BGP next-hop.

RP/0/RP0/CPU0:R4# show cef vrf vrf_cust1

Prefix Next Hop Interface

------------------- ------------------- ------------------

0.0.0.0/0 drop default handler

0.0.0.0/32

40.4.101.0/24 broadcast attached TenGigE0/0/0/0.101

40.4.101.0/32

40.4.101.4/32

40.4.101.11/32 broadcast receive

40.4.101.11/32

TenGigE0/0/0/0.101

40.4.101.255/32

44.1.1.0/24

55.1.1.0/24

88.1.1.0/24

99.1.1.0/24

224.0.0.0/4 broadcast

40.4.101.11/32

1.1.1.9/32

0.0.0.0/32

224.0.0.0/24 receive

255.255.255.255/32 broadcast

TenGigE0/0/0/0.101

1.1.1.5/32 <recursive>

24036 (via-label) <recursive>

The following output displays CEF details for prefix 88.1.1.0/24. Note that the prefix is associated with an

SR policy with BSID value of 24036.

RP/0/RP0/CPU0:R4# show cef vrf vrf_cust1 88.1.1.0/24

88.1.1.0/24, version 51, internal 0x5000001 0x0 (ptr 0x98c60ddc) [1], 0x0 (0x0), 0x208

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(0x98425268)

Updated May 20 09:23:34.216

Prefix Len 24, traffic index 0, precedence n/a, priority 3 via local-label 24036, 5 dependencies, recursive [flags 0x6000] path-idx 0 NHID 0x0 [0x97091ec0 0x0] recursion-via-label next hop VRF - 'default', table - 0xe0000000 next hop via 24036/0/21 next hop srte_c_10_ep labels imposed {ImplNull 24012}

Verifying SR Policy

Use the show segment-routing traffic-eng policy command to display SR policy information.

The following outputs show the details of an on-demand SR policy that was triggered by prefixes with color

10 advertised by node 1.1.1.8.

RP/0/RP0/CPU0:R4# show segment-routing traffic-eng policy color 10 tabular

Color Endpoint Admin Oper Binding

State State SID

------ -------------------- ------ ------ --------------------

10 1.1.1.8

up up 24036

The following outputs show the details of the on-demand SR policy for BSID 24036.

Note There are 2 candidate paths associated with this SR policy: the path that is computed by the head-end router

(with preference 200), and the path that is computed by the SR-PCE (with preference 100). The candidate path with the highest preference is the active candidate path (highlighted below) and is installed in forwarding.

RP/0/RP0/CPU0:R4# show segment-routing traffic-eng policy binding-sid 24036

SR-TE policy database

---------------------

Color: 10, End-point: 1.1.1.8

Name: srte_c_10_ep_1.1.1.8

Status:

Admin: up Operational: up for 4d14h (since Jul 3 20:28:57.840)

Candidate-paths:

Preference: 200 (BGP ODN) (active)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_10_ep_1.1.1.8_discr_200

PLSP-ID: 12

Dynamic (valid)

Metric Type: TE, Path Accumulated Metric: 30

16009 [Prefix-SID, 1.1.1.9]

16008 [Prefix-SID, 1.1.1.8]

Preference: 100 (BGP ODN)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_10_ep_1.1.1.8_discr_100

PLSP-ID: 11

Dynamic (pce 1.1.1.57) (valid)

Metric Type: TE, Path Accumulated Metric: 30

16009 [Prefix-SID, 1.1.1.9]

16008 [Prefix-SID, 1.1.1.8]

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Configuring SR-ODN for EVPN-VPWS: Use Case

Attributes:

Binding SID: 24036

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

Verifying SR Policy Forwarding

Use the show segment-routing traffic-eng forwarding policy command to display the SR policy forwarding information.

The following outputs show the forwarding details for an on-demand SR policy that was triggered by prefixes with color 10 advertised by node 1.1.1.8.

RP/0/RP0/CPU0:R4# show segment-routing traffic-eng forwarding policy binding-sid 24036 tabular

Color Endpoint Segment Outgoing Outgoing Next Hop Bytes Pure

List Label Interface Switched Backup

----- --------------- ------------ -------- ------------ ------------ ------------ ------

10 1.1.1.8

dynamic 16009 Gi0/0/0/4 10.4.5.5

16001 Gi0/0/0/5 11.4.8.8

0 Yes

RP/0/RP0/CPU0:R4# show segment-routing traffic-eng forwarding policy binding-sid 24036 detail

Mon Jul 8 11:56:46.887 PST

SR-TE Policy Forwarding database

--------------------------------

Color: 10, End-point: 1.1.1.8

Name: srte_c_10_ep_1.1.1.8

Binding SID: 24036

Segment Lists:

SL[0]:

Name: dynamic

Paths:

Path[0]:

Outgoing Label: 16009

Outgoing Interface: GigabitEthernet0/0/0/4

Next Hop: 10.4.5.5

Switched Packets/Bytes: 0/0

FRR Pure Backup: No

Label Stack (Top -> Bottom): { 16009, 16008 }

Path-id: 1 (Protected), Backup-path-id: 2, Weight: 64

Path[1]:

Outgoing Label: 16001

Outgoing Interface: GigabitEthernet0/0/0/5

Next Hop: 11.4.8.8

Switched Packets/Bytes: 0/0

FRR Pure Backup: Yes

Label Stack (Top -> Bottom): { 16001, 16009, 16008 }

Path-id: 2 (Pure-Backup), Weight: 64

Policy Packets/Bytes Switched: 0/0

Local label: 80013

Configuring SR-ODN for EVPN-VPWS: Use Case

This use case shows how to set up a pair of ELINE services using EVPN-VPWS between two sites. Services are carried over SR policies that must not share any common links along their paths (link-disjoint). The SR policies are triggered on-demand based on ODN principles. An SR-PCE computes the disjoint paths.

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Configuring SR-ODN for EVPN-VPWS: Use Case

This use case uses the following topology with 2 sites: Site 1 with nodes A and B, and Site 2 with nodes C and D.

Figure 3: Topology for Use Case: SR-ODN for EVPN-VPWS

Table 2: Use Case Parameters

IP Addresses of

Loopback0 (Lo0)

Interfaces

SR-PCE Lo0: 1.1.1.207

Site 1:

• Node A Lo0: 1.1.1.5

• Node B Lo0: 1.1.1.6

EVPN-VPWS Service

Parameters

ELINE-1:

• EVPN-VPWS EVI 100

• Node A: AC-ID = 11

• Node C: AC-ID = 21

ODN BGP Color Extended

Communities

Site 1 routers (Nodes A and B):

• set color 10000

• match color 11000

Site 2:

• Node C Lo0: 1.1.1.2

• Node D Lo0: 1.1.1.4

ELINE-2:

• EVPN-VPWS EVI 101

• Node B: AC-ID = 12

• Node D: AC-ID = 22

Site 2 routers (Nodes C and D):

• set color 11000

• match color 10000

Note These colors are associated with the EVPN route-type 1 routes of the EVPN-VPWS services.

PCEP LSP Disjoint-Path

Association Group ID

Site 1 to Site 2 LSPs (from Node A to Node C/from

Node B to Node D):

Site 2 to Site 1 LSPs (from Node C to Node A/from

Node D to Node B):

• group-id = 775 • group-id = 776

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The use case provides configuration and verification outputs for all devices.

Configuration Verification

Configuration: SR-PCE, on page 49

Configuration: Site 1 Node A, on page 49

Verification: SR-PCE, on page 53

Verification: Site 1 Node A, on page 57

Configuration: Site 1 Node B, on page 50

Configuration: Site 2 Node C, on page 51

Configuration: Site 2 Node D, on page 52

Verification: Site 1 Node B, on page 60

Verification: Site 2 Node C, on page 63

Verification: Site 2 Node D, on page 65

Configuration: SR-PCE

For cases when PCC nodes support, or signal, PCEP association-group object to indicate the pair of LSPs in a disjoint set, there is no extra configuration required at the SR-PCE to trigger disjoint-path computation.

Note SR-PCE also supports disjoint-path computation for cases when PCC nodes do not support PCEP association-group object. See

Configure the Disjoint Policy (Optional), on page 122

for more information.

Configuration: Site 1 Node A

This section depicts relevant configuration of Node A at Site 1. It includes service configuration, BGP color extended community, and RPL. It also includes the corresponding ODN template required to achieve the disjointness SLA.

Nodes in Site 1 are configured to set color 10000 on originating EVPN routes, while matching color 11000 on incoming EVPN routes from routers located at Site 2.

Since both nodes in Site 1 request path computation from SR-PCE using the same disjoint-path group-id

(775), the PCE will attempt to compute disjointness for the pair of LSPs originating from Site 1 toward Site

/* EVPN-VPWS configuration */ interface GigabitEthernet0/0/0/3.2500 l2transport

encapsulation dot1q 2500 rewrite ingress tag pop 1 symmetric l2vpn xconnect group evpn_vpws_group

p2p evpn_vpws_100 interface GigabitEthernet0/0/0/3.2500

neighbor evpn evi 100 target 21 source 11

/* BGP color community and RPL configuration */ extcommunity-set opaque color-10000

10000 end-set

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route-policy SET_COLOR_EVPN_VPWS if evpn-route-type is 1 and rd in (ios-regex '.*..*..*..*:( 100 )') then set extcommunity color color-10000 endif pass end-policy

router bgp 65000 neighbor 1.1.1.253

address-family l2vpn evpn

route-policy SET_COLOR_EVPN_VPWS out

/* ODN template configuration */ segment-routing traffic-eng on-demand color 11000 dynamic pcep

metric type igp

disjoint-path group-id 775 type link

Configuration: Site 1 Node B

This section depicts relevant configuration of Node B at Site 1.

/* EVPN-VPWS configuration */ interface TenGigE0/3/0/0/8.2500 l2transport encapsulation dot1q 2500 rewrite ingress tag pop 1 symmetric

l2vpn xconnect group evpn_vpws_group p2p evpn_vpws_101 interface TenGigE0/3/0/0/8.2500

neighbor evpn evi 101 target 22 source 12

/* BGP color community and RPL configuration */ extcommunity-set opaque color-10000

10000 end-set

route-policy SET_COLOR_EVPN_VPWS if evpn-route-type is 1 and rd in (ios-regex '.*..*..*..*:( 101 )') then set extcommunity color color-10000 endif pass

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router bgp 65000 neighbor 1.1.1.253

address-family l2vpn evpn route-policy SET_COLOR_EVPN_VPWS out

/* ODN template configuration */ segment-routing traffic-eng on-demand color 11000 dynamic pcep

metric

type igp disjoint-path group-id 775 type link

Configuration: Site 2 Node C

This section depicts relevant configuration of Node C at Site 2. It includes service configuration, BGP color extended community, and RPL. It also includes the corresponding ODN template required to achieve the disjointness SLA.

Nodes in Site 2 are configured to set color 11000 on originating EVPN routes, while matching color 10000 on incoming EVPN routes from routers located at Site 1.

Since both nodes on Site 2 request path computation from SR-PCE using the same disjoint-path group-id

(776), the PCE will attempt to compute disjointness for the pair of LSPs originating from Site 2 toward Site

/* EVPN-VPWS configuration */ interface GigabitEthernet0/0/0/3.2500 l2transport

encapsulation dot1q 2500 rewrite ingress tag pop 1 symmetric l2vpn xconnect group evpn_vpws_group

p2p evpn_vpws_100 interface GigabitEthernet0/0/0/3.2500

neighbor evpn evi 100 target 11 source 21

/* BGP color community and RPL configuration */ extcommunity-set opaque color-11000

11000 end-set

route-policy SET_COLOR_EVPN_VPWS

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure SR-TE Policies

Configuring SR-ODN for EVPN-VPWS: Use Case if evpn-route-type is 1 and rd in (ios-regex '.*..*..*..*:( 100 )') then set extcommunity color color-11000 endif pass end-policy

router bgp 65000

neighbor 1.1.1.253

address-family l2vpn evpn

route-policy SET_COLOR_EVPN_VPWS out

/* ODN template configuration */ segment-routing traffic-eng on-demand color 10000 dynamic pcep

metric type igp

disjoint-path group-id 776 type link

Configuration: Site 2 Node D

This section depicts relevant configuration of Node D at Site 2.

/* EVPN-VPWS configuration */ interface GigabitEthernet0/0/0/1.2500 l2transport encapsulation dot1q 2500 rewrite ingress tag pop 1 symmetric

l2vpn xconnect group evpn_vpws_group p2p evpn_vpws_101 interface GigabitEthernet0/0/0/1.2500

neighbor evpn evi 101 target 12 source 22

/* BGP color community and RPL configuration */ extcommunity-set opaque color-11000

11000 end-set

route-policy SET_COLOR_EVPN_VPWS if evpn-route-type is 1 and rd in (ios-regex '.*..*..*..*:( 101 )') then set extcommunity color color-11000 endif pass end-policy

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure SR-TE Policies

Configuring SR-ODN for EVPN-VPWS: Use Case router bgp 65000 neighbor 1.1.1.253

address-family l2vpn evpn route-policy SET_COLOR_EVPN_VPWS out

/* ODN template configuration */ segment-routing traffic-eng on-demand color 10000 dynamic pcep

metric

type igp

disjoint-path group-id 776 type link

Verification: SR-PCE

Use the show pce ipv4 peer command to display the SR-PCE’s PCEP peers and session status. SR-PCE performs path computation for the 4 nodes depicted in the use-case.

RP/0/0/CPU0:SR-PCE# show pce ipv4 peer

Mon Jul 15 19:41:43.622 UTC

PCE's peer database:

--------------------

Peer address: 1.1.1.2

State: Up

Capabilities: Stateful, Segment-Routing, Update, Instantiation

Peer address: 1.1.1.4

State: Up

Capabilities: Stateful, Segment-Routing, Update, Instantiation

Peer address: 1.1.1.5

State: Up

Capabilities: Stateful, Segment-Routing, Update, Instantiation

Peer address: 1.1.1.6

State: Up

Capabilities: Stateful, Segment-Routing, Update, Instantiation

Use the show pce association group-id command to display information for the pair of LSPs assigned to a given association group-id value.

Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. In particular, disjoint LSPs from site 1 to site 2 are identified by association group-id 775. The output includes high-level information for LSPs associated to this group-id:

• At Node A (1.1.1.5): LSP symbolic name = bgp_c_11000_ep_1.1.1.2_discr_100

• At Node B (1.1.1.6): LSP symbolic name = bgp_c_11000_ep_1.1.1.4_discr_100

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

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Configuring SR-ODN for EVPN-VPWS: Use Case

In this case, the SR-PCE was able to achieve the desired disjointness level; therefore the Status is shown as

"Satisfied".

RP/0/0/CPU0:SR-PCE# show pce association group-id 775

Thu Jul 11 03:52:20.770 UTC

PCE's association database:

----------------------

Association: Type Link-Disjoint, Group 775 , Not Strict

Associated LSPs:

LSP[0]:

PCC 1.1.1.6, tunnel name bgp_c_11000_ep_1.1.1.4_discr_100

, PLSP ID 18, tunnel ID 17,

LSP ID 3, Configured on PCC

LSP[1]:

PCC 1.1.1.5, tunnel name bgp_c_11000_ep_1.1.1.2_discr_100

, PLSP ID 18, tunnel ID 18,

LSP ID 3, Configured on PCC

Status: Satisfied

Use the show pce lsp command to display detailed information of an LSP present in the PCE's LSP database.

This output shows details for the LSP at Node A (1.1.1.5) that is used to carry traffic of EVPN VPWS EVI

100 towards node C (1.1.1.2).

RP/0/0/CPU0:SR-PCE# show pce lsp pcc ipv4 1.1.1.5 name bgp_c_11000_ep_1.1.1.2_discr_100

Thu Jul 11 03:58:45.903 UTC

PCE's tunnel database:

----------------------

PCC 1.1.1.5:

Tunnel Name: bgp_c_11000_ep_1.1.1.2_discr_100

Color: 11000

Interface Name: srte_c_11000_ep_1.1.1.2

LSPs:

LSP[0]: source 1.1.1.5, destination 1.1.1.2, tunnel ID 18, LSP ID 3

State: Admin up, Operation up

Setup type: Segment Routing

Binding SID: 80037

Maximum SID Depth: 10

Absolute Metric Margin: 0

Relative Metric Margin: 0%

Preference: 100

Bandwidth: signaled 0 kbps, applied 0 kbps

PCEP information:

PLSP-ID 0x12, flags: D:1 S:0 R:0 A:1 O:1 C:0

LSP Role: Exclude LSP

State-sync PCE: None

PCC: 1.1.1.5

LSP is subdelegated to: None

Reported path:

Metric type: IGP, Accumulated Metric 40

SID[0]: Adj, Label 80003, Address: local 11.5.8.5 remote 11.5.8.8

SID[1]: Node, Label 16007, Address 1.1.1.7

SID[2]: Node, Label 16002, Address 1.1.1.2

Computed path: (Local PCE)

Computed Time: Thu Jul 11 03:49:48 UTC 2019 (00:08:58 ago)

Metric type: IGP, Accumulated Metric 40

SID[0]: Adj, Label 80003, Address: local 11.5.8.5 remote 11.5.8.8

SID[1]: Node, Label 16007, Address 1.1.1.7

SID[2]: Node, Label 16002, Address 1.1.1.2

Recorded path:

None

Disjoint Group Information :

Type Link-Disjoint, Group 775

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

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Configuring SR-ODN for EVPN-VPWS: Use Case

This output shows details for the LSP at Node B (1.1.1.6) that is used to carry traffic of EVPN VPWS EVI

101 towards node D (1.1.1.4).

RP/0/0/CPU0:SR-PCE# show pce lsp pcc ipv4 1.1.1.6 name bgp_c_11000_ep_1.1.1.4_discr_100

Thu Jul 11 03:58:56.812 UTC

PCE's tunnel database:

----------------------

PCC 1.1.1.6:

Tunnel Name: bgp_c_11000_ep_1.1.1.4_discr_100

Color: 11000

Interface Name: srte_c_11000_ep_1.1.1.4

LSPs:

LSP[0]: source 1.1.1.6, destination 1.1.1.4, tunnel ID 17, LSP ID 3

State: Admin up, Operation up

Setup type: Segment Routing

Binding SID: 80061

Maximum SID Depth: 10

Absolute Metric Margin: 0

Relative Metric Margin: 0%

Preference: 100

Bandwidth: signaled 0 kbps, applied 0 kbps

PCEP information:

PLSP-ID 0x12, flags: D:1 S:0 R:0 A:1 O:1 C:0

LSP Role: Disjoint LSP

State-sync PCE: None

PCC: 1.1.1.6

LSP is subdelegated to: None

Reported path:

Metric type: IGP, Accumulated Metric 40

SID[0]: Node, Label 16001, Address 1.1.1.1

SID[1]: Node, Label 16004, Address 1.1.1.4

Computed path: (Local PCE)

Computed Time: Thu Jul 11 03:49:48 UTC 2019 (00:09:08 ago)

Metric type: IGP, Accumulated Metric 40

SID[0]: Node, Label 16001, Address 1.1.1.1

SID[1]: Node, Label 16004, Address 1.1.1.4

Recorded path:

None

Disjoint Group Information :

Type Link-Disjoint, Group 775

Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. In particular, disjoint LSPs from site 2 to site 1 are identified by association group-id 776. The output includes high-level information for LSPs associated to this group-id:

• At Node C (1.1.1.2): LSP symbolic name = bgp_c_10000_ep_1.1.1.5_discr_100

• At Node D (1.1.1.4): LSP symbolic name = bgp_c_10000_ep_1.1.1.6_discr_100

In this case, the SR-PCE was able to achieve the desired disjointness level; therefore, the Status is shown as

"Satisfied".

RP/0/0/CPU0:SR-PCE# show pce association group-id 776

Thu Jul 11 03:52:24.370 UTC

PCE's association database:

----------------------

Association: Type Link-Disjoint, Group 776 , Not Strict

Associated LSPs:

LSP[0]:

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure SR-TE Policies

Configuring SR-ODN for EVPN-VPWS: Use Case

PCC 1.1.1.4, tunnel name bgp_c_10000_ep_1.1.1.6_discr_100

, PLSP ID 16, tunnel ID 14,

LSP ID 1, Configured on PCC

LSP[1]:

PCC 1.1.1.2, tunnel name bgp_c_10000_ep_1.1.1.5_discr_100

, PLSP ID 6, tunnel ID 21, LSP

ID 3, Configured on PCC

Status: Satisfied

Use the show pce lsp command to display detailed information of an LSP present in the PCE's LSP database.

This output shows details for the LSP at Node C (1.1.1.2) that is used to carry traffic of EVPN VPWS EVI

100 towards node A (1.1.1.5).

RP/0/0/CPU0:SR-PCE# show pce lsp pcc ipv4 1.1.1.2 name bgp_c_10000_ep_1.1.1.5_discr_100

Thu Jul 11 03:55:21.706 UTC

PCE's tunnel database:

----------------------

PCC 1.1.1.2:

Tunnel Name: bgp_c_10000_ep_1.1.1.5_discr_100

Color: 10000

Interface Name: srte_c_10000_ep_1.1.1.5

LSPs:

LSP[0]: source 1.1.1.2, destination 1.1.1.5, tunnel ID 21, LSP ID 3

State: Admin up, Operation up

Setup type: Segment Routing

Binding SID: 80052

Maximum SID Depth: 10

Absolute Metric Margin: 0

Relative Metric Margin: 0%

Preference: 100

Bandwidth: signaled 0 kbps, applied 0 kbps

PCEP information:

PLSP-ID 0x6, flags: D:1 S:0 R:0 A:1 O:1 C:0

LSP Role: Exclude LSP

State-sync PCE: None

PCC: 1.1.1.2

LSP is subdelegated to: None

Reported path:

Metric type: IGP, Accumulated Metric 40

SID[0]: Node, Label 16007, Address 1.1.1.7

SID[1]: Node, Label 16008, Address 1.1.1.8

SID[2]: Adj, Label 80005, Address: local 11.5.8.8 remote 11.5.8.5

Computed path: (Local PCE)

Computed Time: Thu Jul 11 03:50:03 UTC 2019 (00:05:18 ago)

Metric type: IGP, Accumulated Metric 40

SID[0]: Node, Label 16007, Address 1.1.1.7

SID[1]: Node, Label 16008, Address 1.1.1.8

SID[2]: Adj, Label 80005, Address: local 11.5.8.8 remote 11.5.8.5

Recorded path:

None

Disjoint Group Information :

Type Link-Disjoint, Group 776

This output shows details for the LSP at Node D (1.1.1.4) used to carry traffic of EVPN VPWS EVI 101 towards node B (1.1.1.6).

RP/0/0/CPU0:SR-PCE# show pce lsp pcc ipv4 1.1.1.4 name bgp_c_10000_ep_1.1.1.6_discr_100

Thu Jul 11 03:55:23.296 UTC

PCE's tunnel database:

----------------------

PCC 1.1.1.4:

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure SR-TE Policies

Configuring SR-ODN for EVPN-VPWS: Use Case

Tunnel Name: bgp_c_10000_ep_1.1.1.6_discr_100

Color: 10000

Interface Name: srte_c_10000_ep_1.1.1.6

LSPs:

LSP[0]: source 1.1.1.4, destination 1.1.1.6, tunnel ID 14, LSP ID 1

State: Admin up, Operation up

Setup type: Segment Routing

Binding SID: 80047

Maximum SID Depth: 10

Absolute Metric Margin: 0

Relative Metric Margin: 0%

Preference: 100

Bandwidth: signaled 0 kbps, applied 0 kbps

PCEP information:

PLSP-ID 0x10, flags: D:1 S:0 R:0 A:1 O:1 C:0

LSP Role: Disjoint LSP

State-sync PCE: None

PCC: 1.1.1.4

LSP is subdelegated to: None

Reported path:

Metric type: IGP, Accumulated Metric 40

SID[0]: Node, Label 16001, Address 1.1.1.1

SID[1]: Node, Label 16006, Address 1.1.1.6

Computed path: (Local PCE)

Computed Time: Thu Jul 11 03:50:03 UTC 2019 (00:05:20 ago)

Metric type: IGP, Accumulated Metric 40

SID[0]: Node, Label 16001, Address 1.1.1.1

SID[1]: Node, Label 16006, Address 1.1.1.6

Recorded path:

None

Disjoint Group Information :

Type Link-Disjoint, Group 776

Verification: Site 1 Node A

This section depicts verification steps at Node A.

Use the show bgp l2vpn evpn command to display BGP prefix information for EVPN-VPWS EVI 100 (rd

1.1.1.5:100). The output includes an EVPN route-type 1 route with color 11000 originated at Node C (1.1.1.2).

RP/0/RSP0/CPU0:Node-A# show bgp l2vpn evpn rd 1.1.1.5:100

Wed Jul 10 18:57:57.704 PST

BGP router identifier 1.1.1.5, local AS number 65000

BGP generic scan interval 60 secs

Non-stop routing is enabled

BGP table state: Active

Table ID: 0x0 RD version: 0

BGP main routing table version 360

BGP NSR Initial initsync version 1 (Reached)

BGP NSR/ISSU Sync-Group versions 0/0

BGP scan interval 60 secs

Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

Route Distinguisher: 1.1.1.5:100 (default for vrf VPWS:100)

*> [1][0000.0000.0000.0000.0000][11]/120

0.0.0.0

*>i[1][0000.0000.0000.0000.0000][21]/120

1.1.1.2 C:11000 100

0 i

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure SR-TE Policies

Configuring SR-ODN for EVPN-VPWS: Use Case

The following output displays the details for the incoming EVPN RT1. Note the presence of BGP extended color community 11000, and that the prefix is associated with an SR policy with color 11000 and BSID value of 80044.

RP/0/RSP0/CPU0:Node-A# show bgp l2vpn evpn rd 1.1.1.5:100

[1][0000.0000.0000.0000.0000][21]/120

Wed Jul 10 18:57:58.107 PST

BGP routing table entry for [1][0000.0000.0000.0000.0000][21]/120, Route Distinguisher:

1.1.1.5:100

Versions:

Process bRIB/RIB SendTblVer

Speaker 360 360

Last Modified: Jul 10 18:36:18.369 for 00:21:40

Paths: (1 available, best #1)

Not advertised to any peer

Path #1: Received by speaker 0

Not advertised to any peer

Local

1.1.1.2 C:11000 (bsid:80044) (metric 40) from 1.1.1.253 (1.1.1.2)

Received Label 80056

Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install

Received Path ID 0, Local Path ID 1, version 358

Extended community: Color:11000 RT:65000:100

Originator: 1.1.1.2, Cluster list: 1.1.1.253

SR policy color 11000, up, registered, bsid 80044 , if-handle 0x00001b20

Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 1.1.1.2:100

Use the show l2vpn xconnect command to display the state associated with EVPN-VPWS EVI 100 service.

RP/0/RSP0/CPU0:Node-A# show l2vpn xconnect group evpn_vpws_group

Wed Jul 10 18:58:02.333 PST

Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,

SB = Standby, SR = Standby Ready, (PP) = Partially Programmed

XConnect

Group Name

Segment 1

ST Description ST

Segment 2

Description ST

-------------------------------------------------------------------------------evpn_vpws_group evpn_vpws_100

UP Gi0/0/0/3.2500

UP EVPN 100,21,1.1.1.2

----------------------------------------------------------------------------------------

The following output shows the details for the service. Note that the service is associated with the on-demand

SR policy with color 11000 and end-point 1.1.1.2 (node C).

RP/0/RSP0/CPU0:Node-A# show l2vpn xconnect group evpn_vpws_group xc-name evpn_vpws_100 detail

Wed Jul 10 18:58:02.755 PST

Group evpn_vpws_group, XC evpn_vpws_100, state is up; Interworking none

AC: GigabitEthernet0/0/0/3.2500, state is up

Type VLAN; Num Ranges: 1

Rewrite Tags: []

VLAN ranges: [2500, 2500]

MTU 1500; XC ID 0x120000c; interworking none

Statistics: packets: received 0, sent 0 bytes: received 0, sent 0 drops: illegal VLAN 0, illegal length 0

EVPN: neighbor 1.1.1.2, PW ID: evi 100, ac-id 21, state is up ( established )

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure SR-TE Policies

Configuring SR-ODN for EVPN-VPWS: Use Case

XC ID 0xa0000007

Encapsulation MPLS

Source address 1.1.1.5

Encap type Ethernet, control word enabled

Sequencing not set

Preferred path Active : SR TE srte_c_11000_ep_1.1.1.2, On-Demand , fallback enabled

Tunnel : Up

Load Balance Hashing: src-dst-mac

EVPN Local Remote

------------ ------------------------------ -----------------------------

Label

MTU

80040

1500

80056

1500

Control word enabled

AC ID 11

EVPN type Ethernet enabled

Ethernet

------------ ------------------------------ -----------------------------

Create time: 10/07/2019 18:31:30 (1d17h ago)

Last time status changed: 10/07/2019 19:42:00 (1d16h ago)

Last time PW went down: 10/07/2019 19:40:55 (1d16h ago)

Statistics: packets: received 0, sent 0 bytes: received 0, sent 0

Use the show segment-routing traffic-eng policy command with tabular option to display SR policy summary information.

The following output shows the on-demand SR policy with BSID 80044 that was triggered by EVPN RT1 prefix with color 11000 advertised by node C (1.1.1.2).

RP/0/RSP0/CPU0:Node-A# show segment-routing traffic-eng policy color 11000 tabular

Wed Jul 10 18:58:00.732 PST

Color Endpoint Admin Oper Binding

State State SID

------ -------------------- ------ ------ --------------------

11000 1.1.1.2

up up 80044

The following output shows the details for the on-demand SR policy. Note that the SR policy's active candidate path (preference 100) is computed by SR-PCE (1.1.1.207).

Based on the goals of this use case, SR-PCE computes link-disjoint paths for the SR policies associated with a pair of ELINE services between site 1 and site 2. Specifically, from site 1 to site 2, LSP at Node A

(srte_c_11000_ep_1.1.1.2) is link-disjoint from LSP at Node B (srte_c_11000_ep_1.1.1.4).

RP/0/RSP0/CPU0:Node-A# show segment-routing traffic-eng policy color 11000

Wed Jul 10 19:15:47.217 PST

SR-TE policy database

---------------------

Color: 11000, End-point: 1.1.1.2

Name: srte_c_11000_ep_1.1.1.2

Status:

Admin: up Operational: up for 00:39:31 (since Jul 10 18:36:00.471)

Candidate-paths:

Preference: 200 (BGP ODN) (shutdown)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_11000_ep_1.1.1.2_discr_200

PLSP-ID: 19

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

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Configuring SR-ODN for EVPN-VPWS: Use Case

Dynamic (invalid)

Preference: 100 (BGP ODN) (active)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_11000_ep_1.1.1.2_discr_100

PLSP-ID: 18

Dynamic (pce 1.1.1.207) (valid)

Metric Type: IGP, Path Accumulated Metric: 40

80003 [Adjacency-SID, 11.5.8.5 - 11.5.8.8]

16007 [Prefix-SID, 1.1.1.7]

16002 [Prefix-SID, 1.1.1.2]

Attributes:

Binding SID: 80044

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

Verification: Site 1 Node B

This section depicts verification steps at Node B.

Use the show bgp l2vpn evpn command to display BGP prefix information for EVPN-VPWS EVI 101 (rd

1.1.1.6:101). The output includes an EVPN route-type 1 route with color 11000 originated at Node D (1.1.1.4).

RP/0/RSP0/CPU0:Node-B# show bgp l2vpn evpn rd 1.1.1.6:101

Wed Jul 10 19:08:54.964 PST

BGP router identifier 1.1.1.6, local AS number 65000

BGP generic scan interval 60 secs

Non-stop routing is enabled

BGP table state: Active

Table ID: 0x0 RD version: 0

BGP main routing table version 322

BGP NSR Initial initsync version 7 (Reached)

BGP NSR/ISSU Sync-Group versions 0/0

BGP scan interval 60 secs

Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

Route Distinguisher: 1.1.1.6:101 (default for vrf VPWS:101)

*> [1][0000.0000.0000.0000.0000][12]/120

0.0.0.0

*>i[1][0000.0000.0000.0000.0000][22]/120

1.1.1.4 C:11000 100

0 i

Processed 2 prefixes, 2 paths

RP/0/RSP0/CPU0:Node-B# show bgp l2vpn evpn rd 1.1.1.6:101

[1][0000.0000.0000.0000.0000][22]/120

Wed Jul 10 19:08:55.039 PST

BGP routing table entry for [1][0000.0000.0000.0000.0000][22]/120, Route Distinguisher:

1.1.1.6:101

Versions:

Process

Speaker bRIB/RIB SendTblVer

322 322

Last Modified: Jul 10 18:42:10.408 for 00:26:44

Paths: (1 available, best #1)

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Configuring SR-ODN for EVPN-VPWS: Use Case

Not advertised to any peer

Path #1: Received by speaker 0

Not advertised to any peer

Local

1.1.1.4 C:11000 (bsid:80061) (metric 40) from 1.1.1.253 (1.1.1.4)

Received Label 80045

Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install

Received Path ID 0, Local Path ID 1, version 319

Extended community: Color:11000 RT:65000:101

Originator: 1.1.1.4, Cluster list: 1.1.1.253

SR policy color 11000, up, registered, bsid 80061 , if-handle 0x00000560

Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 1.1.1.4:101

Use the show l2vpn xconnect command to display the state associated with EVPN-VPWS EVI 101 service.

RP/0/RSP0/CPU0:Node-B# show l2vpn xconnect group evpn_vpws_group

Wed Jul 10 19:08:56.388 PST

Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,

SB = Standby, SR = Standby Ready, (PP) = Partially Programmed

XConnect

Group Name

Segment 1

ST Description ST

Segment 2

Description ST

-------------------------------------------------------------------------------evpn_vpws_group evpn_vpws_101

UP Te0/3/0/0/8.2500

UP EVPN 101,22,1.1.1.4

----------------------------------------------------------------------------------------

The following output shows the details for the service. Note that the service is associated with the on-demand

SR policy with color 11000 and end-point 1.1.1.4 (node D).

RP/0/RSP0/CPU0:Node-B# show l2vpn xconnect group evpn_vpws_group xc-name evpn_vpws_101

Wed Jul 10 19:08:56.511 PST

Group evpn_vpws_group, XC evpn_vpws_101, state is up; Interworking none

AC: TenGigE0/3/0/0/8.2500, state is up

Type VLAN; Num Ranges: 1

Rewrite Tags: []

VLAN ranges: [2500, 2500]

MTU 1500; XC ID 0x2a0000e; interworking none

Statistics: packets: received 0, sent 0 bytes: received 0, sent 0 drops: illegal VLAN 0, illegal length 0

EVPN: neighbor 1.1.1.4, PW ID: evi 101, ac-id 22, state is up ( established )

XC ID 0xa0000009

Encapsulation MPLS

Source address 1.1.1.6

Encap type Ethernet, control word enabled

Sequencing not set

Preferred path Active : SR TE srte_c_11000_ep_1.1.1.4, On-Demand , fallback enabled

Tunnel : Up

Load Balance Hashing: src-dst-mac

EVPN Local Remote

------------ ------------------------------ -----------------------------

Label 80060 80045

MTU 1500

Control word enabled

AC ID 12

EVPN type Ethernet

1500 enabled

Ethernet

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------------ ------------------------------ -----------------------------

Create time: 10/07/2019 18:32:49 (00:36:06 ago)

Last time status changed: 10/07/2019 18:42:07 (00:26:49 ago)

Statistics: packets: received 0, sent 0 bytes: received 0, sent 0

Use the show segment-routing traffic-eng policy command with tabular option to display SR policy summary information.

The following output shows the on-demand SR policy with BSID 80061 that was triggered by EVPN RT1 prefix with color 11000 advertised by node D (1.1.1.4).

RP/0/RSP0/CPU0:Node-B# show segment-routing traffic-eng policy color 11000 tabular

Wed Jul 10 19:08:56.146 PST

Color Endpoint Admin Oper

State State

Binding

SID

------ -------------------- ------ ------ --------------------

11000 1.1.1.4

up up 80061

The following output shows the details for the on-demand SR policy. Note that the SR policy's active candidate path (preference 100) is computed by SR-PCE (1.1.1.207).

(srte_c_11000_ep_1.1.1.4) is link-disjoint from LSP at Node A (srte_c_11000_ep_1.1.1.2).

RP/0/RSP0/CPU0:Node-B# show segment-routing traffic-eng policy color 11000

Wed Jul 10 19:08:56.207 PST

SR-TE policy database

---------------------

Color: 11000, End-point: 1.1.1.4

Name: srte_c_11000_ep_1.1.1.4

Status:

Admin: up Operational: up for 00:26:47 (since Jul 10 18:40:05.868)

Candidate-paths:

Preference: 200 (BGP ODN) (shutdown)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_11000_ep_1.1.1.4_discr_200

PLSP-ID: 19

Dynamic (invalid)

Preference: 100 (BGP ODN) (active)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_11000_ep_1.1.1.4_discr_100

PLSP-ID: 18

Dynamic (pce 1.1.1.207) (valid)

Metric Type: IGP, Path Accumulated Metric: 40

16001 [Prefix-SID, 1.1.1.1]

16004 [Prefix-SID, 1.1.1.4]

Attributes:

Binding SID: 80061

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

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Configuring SR-ODN for EVPN-VPWS: Use Case

Verification: Site 2 Node C

This section depicts verification steps at Node C.

Use the show bgp l2vpn evpn command to display BGP prefix information for EVPN-VPWS EVI 100 (rd

1.1.1.2:100). The output includes an EVPN route-type 1 route with color 10000 originated at Node A (1.1.1.5).

RP/0/RSP0/CPU0:Node-C# show bgp l2vpn evpn rd 1.1.1.2:100

BGP router identifier 1.1.1.2, local AS number 65000

BGP generic scan interval 60 secs

Non-stop routing is enabled

BGP table state: Active

Table ID: 0x0 RD version: 0

BGP main routing table version 21

BGP NSR Initial initsync version 1 (Reached)

BGP NSR/ISSU Sync-Group versions 0/0

BGP scan interval 60 secs

Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

Route Distinguisher: 1.1.1.2:100 (default for vrf VPWS:100)

*>i[1][0000.0000.0000.0000.0000][11]/120

1.1.1.5 C:10000 100

*> [1][0000.0000.0000.0000.0000][21]/120

0.0.0.0

0 i

The following output displays the details for the incoming EVPN RT1. Note the presence of BGP extended color community 10000, and that the prefix is associated with an SR policy with color 10000 and BSID value of 80058.

RP/0/RSP0/CPU0:Node-C# show bgp l2vpn evpn rd 1.1.1.2:100

[1][0000.0000.0000.0000.0000][11]/120

BGP routing table entry for [1][0000.0000.0000.0000.0000][11]/120, Route Distinguisher:

1.1.1.2:100

Versions:

Process

Speaker bRIB/RIB SendTblVer

20 20

Last Modified: Jul 10 18:36:20.503 for 00:45:21

Paths: (1 available, best #1)

Not advertised to any peer

Path #1: Received by speaker 0

Not advertised to any peer

Local

1.1.1.5 C:10000 (bsid:80058) (metric 40) from 1.1.1.253 (1.1.1.5)

Received Label 80040

Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install

Received Path ID 0, Local Path ID 1, version 18

Extended community: Color:10000 RT:65000:100

Originator: 1.1.1.5, Cluster list: 1.1.1.253

SR policy color 10000, up, registered, bsid 80058 , if-handle 0x000006a0

Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 1.1.1.5:100

Use the show l2vpn xconnect command to display the state associated with EVPN-VPWS EVI 100 service.

RP/0/RSP0/CPU0:Node-C# show l2vpn xconnect group evpn_vpws_group

Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,

SB = Standby, SR = Standby Ready, (PP) = Partially Programmed

XConnect Segment 1 Segment 2

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Group Name ST Description ST Description ST

-------------------------------------------------------------------------------evpn_vpws_group evpn_vpws_100

UP Gi0/0/0/3.2500

UP EVPN 100,11,1.1.1.5

----------------------------------------------------------------------------------------

The following output shows the details for the service. Note that the service is associated with the on-demand

SR policy with color 10000 and end-point 1.1.1.5 (node A).

RP/0/RSP0/CPU0:Node-C# show l2vpn xconnect group evpn_vpws_group xc-name evpn_vpws_100

Group evpn_vpws_group, XC evpn_vpws_100, state is up; Interworking none

AC: GigabitEthernet0/0/0/3.2500, state is up

Type VLAN; Num Ranges: 1

Rewrite Tags: []

VLAN ranges: [2500, 2500]

MTU 1500; XC ID 0x1200008; interworking none

Statistics: packets: received 0, sent 0 bytes: received 0, sent 0 drops: illegal VLAN 0, illegal length 0

EVPN: neighbor 1.1.1.5, PW ID: evi 100, ac-id 11, state is up ( established )

XC ID 0xa0000003

Encapsulation MPLS

Source address 1.1.1.2

Encap type Ethernet, control word enabled

Sequencing not set

Preferred path Active : SR TE srte_c_10000_ep_1.1.1.5, On-Demand , fallback enabled

Tunnel : Up

Load Balance Hashing: src-dst-mac

EVPN Local Remote

------------ ------------------------------ -----------------------------

Label 80056 80040

MTU 1500

Control word enabled

AC ID

EVPN type

Ethernet

1500 enabled

Ethernet

------------ ------------------------------ -----------------------------

Create time: 10/07/2019 18:36:16 (1d19h ago)

Last time status changed: 10/07/2019 19:41:59 (1d18h ago)

Last time PW went down: 10/07/2019 19:40:54 (1d18h ago)

Statistics: packets: received 0, sent 0 bytes: received 0, sent 0

Use the show segment-routing traffic-eng policy command with tabular option to display SR policy summary information.

The following output shows the on-demand SR policy with BSID 80058 that was triggered by EVPN RT1 prefix with color 10000 advertised by node A (1.1.1.5).

RP/0/RSP0/CPU0:Node-C# show segment-routing traffic-eng policy color 10000 tabular

Color Endpoint Admin Oper Binding

State State SID

------ -------------------- ------ ------ --------------------

10000 1.1.1.5

up up 80058

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Configuring SR-ODN for EVPN-VPWS: Use Case

The following output shows the details for the on-demand SR policy. Note that the SR policy's active candidate path (preference 100) is computed by SR-PCE (1.1.1.207).

(srte_c_10000_ep_1.1.1.5) is link-disjoint from LSP at Node D (srte_c_10000_ep_1.1.1.6).

RP/0/RSP0/CPU0:Node-C# show segment-routing traffic-eng policy color 10000

SR-TE policy database

---------------------

Color: 10000, End-point: 1.1.1.5

Name: srte_c_10000_ep_1.1.1.5

Status:

Admin: up Operational: up for 00:12:35 (since Jul 10 19:49:21.890)

Candidate-paths:

Preference: 200 (BGP ODN) (shutdown)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_10000_ep_1.1.1.5_discr_200

PLSP-ID: 7

Dynamic (invalid)

Preference: 100 (BGP ODN) (active)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_10000_ep_1.1.1.5_discr_100

PLSP-ID: 6

Dynamic (pce 1.1.1.207) (valid)

Metric Type: IGP, Path Accumulated Metric: 40

16007 [Prefix-SID, 1.1.1.7]

16008 [Prefix-SID, 1.1.1.8]

80005 [Adjacency-SID, 11.5.8.8 - 11.5.8.5]

Attributes:

Binding SID: 80058

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

Verification: Site 2 Node D

This section depicts verification steps at Node D.

Use the show bgp l2vpn evpn command to display BGP prefix information for EVPN-VPWS EVI 101 (rd

1.1.1.4:101). The output includes an EVPN route-type 1 route with color 10000 originated at Node B (1.1.1.6).

RP/0/RSP0/CPU0:Node-D# show bgp l2vpn evpn rd 1.1.1.4:101

BGP router identifier 1.1.1.4, local AS number 65000

BGP generic scan interval 60 secs

Non-stop routing is enabled

BGP table state: Active

Table ID: 0x0 RD version: 0

BGP main routing table version 570

BGP NSR Initial initsync version 1 (Reached)

BGP NSR/ISSU Sync-Group versions 0/0

BGP scan interval 60 secs

Status codes: s suppressed, d damped, h history, * valid, > best i - internal, r RIB-failure, S stale, N Nexthop-discard

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

Route Distinguisher: 1.1.1.4:101 (default for vrf VPWS:101)

*>i[1][0000.0000.0000.0000.0000][12]/120

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1.1.1.6 C:10000

*> [1][0000.0000.0000.0000.0000][22]/120

0.0.0.0

Processed 2 prefixes, 2 paths

100 0 i

0 i

RP/0/RSP0/CPU0:Node-D# show bgp l2vpn evpn rd 1.1.1.4:101

[1][0000.0000.0000.0000.0000][12]/120

BGP routing table entry for [1][0000.0000.0000.0000.0000][12]/120, Route Distinguisher:

1.1.1.4:101

Versions:

Process

Speaker bRIB/RIB SendTblVer

569 569

Last Modified: Jul 10 18:42:12.455 for 00:45:38

Paths: (1 available, best #1)

Not advertised to any peer

Path #1: Received by speaker 0

Not advertised to any peer

Local

1.1.1.6 C:10000 (bsid:80047) (metric 40) from 1.1.1.253 (1.1.1.6)

Received Label 80060

Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install

Received Path ID 0, Local Path ID 1, version 568

Extended community: Color:10000 RT:65000:101

Originator: 1.1.1.6, Cluster list: 1.1.1.253

SR policy color 10000, up, registered, bsid 80047 , if-handle 0x00001720

Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 1.1.1.6:101

Use the show l2vpn xconnect command to display the state associated with EVPN-VPWS EVI 101 service.

RP/0/RSP0/CPU0:Node-D# show l2vpn xconnect group evpn_vpws_group

Legend: ST = State, UP = Up, DN = Down, AD = Admin Down, UR = Unresolved,

SB = Standby, SR = Standby Ready, (PP) = Partially Programmed

XConnect

Group Name

Segment 1

ST Description ST ST

-------------------------------------------------------------------------------evpn_vpws_group evpn_vpws_101

Segment 2

Description

UP Gi0/0/0/1.2500

UP EVPN 101,12,1.1.1.6

----------------------------------------------------------------------------------------

The following output shows the details for the service. Note that the service is associated with the on-demand

SR policy with color 10000 and end-point 1.1.1.6 (node B).

RP/0/RSP0/CPU0:Node-D# show l2vpn xconnect group evpn_vpws_group xc-name evpn_vpws_101

Group evpn_vpws_group, XC evpn_vpws_101, state is up; Interworking none

AC: GigabitEthernet0/0/0/1.2500, state is up

Type VLAN; Num Ranges: 1

Rewrite Tags: []

VLAN ranges: [2500, 2500]

MTU 1500; XC ID 0x120000c; interworking none

Statistics: packets: received 0, sent 0 bytes: received 0, sent 0

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Configuring SR-ODN for EVPN-VPWS: Use Case drops: illegal VLAN 0, illegal length 0

EVPN: neighbor 1.1.1.6, PW ID: evi 101, ac-id 12, state is up ( established )

XC ID 0xa000000d

Encapsulation MPLS

Source address 1.1.1.4

Encap type Ethernet, control word enabled

Sequencing not set

Preferred path Active : SR TE srte_c_10000_ep_1.1.1.6, On-Demand , fallback enabled

Tunnel : Up

Load Balance Hashing: src-dst-mac

EVPN Local Remote

------------ ------------------------------ -----------------------------

Label

MTU

80045

1500

Control word enabled

AC ID

EVPN type

Ethernet

80060

1500 enabled

Ethernet

------------ ------------------------------ -----------------------------

Create time: 10/07/2019 18:42:07 (00:45:49 ago)

Last time status changed: 10/07/2019 18:42:09 (00:45:47 ago)

Statistics: packets: received 0, sent 0 bytes: received 0, sent 0

Use the show segment-routing traffic-eng policy command with tabular option to display SR policy summary information.

The following output shows the on-demand SR policy with BSID 80047 that was triggered by EVPN RT1 prefix with color 10000 advertised by node B (1.1.1.6).

RP/0/RSP0/CPU0:Node-D# show segment-routing traffic-eng policy color 10000 tabular

Color Endpoint Admin Oper Binding

State State SID

------ -------------------- ------ ------ --------------------

10000 1.1.1.6

up up 80047

The following output shows the details for the on-demand SR policy. Note that the SR policy's active candidate path (preference 100) is computed by SR-PCE (1.1.1.207).

(srte_c_10000_ep_1.1.1.6) is link-disjoint from LSP at Node C (srte_c_10000_ep_1.1.1.5).

RP/0/RSP0/CPU0:Node-D# show segment-routing traffic-eng policy color 10000

SR-TE policy database

---------------------

Color: 10000, End-point: 1.1.1.6

Name: srte_c_10000_ep_1.1.1.6

Status:

Admin: up Operational: up for 01:23:04 (since Jul 10 18:42:07.350)

Candidate-paths:

Preference: 200 (BGP ODN) (shutdown)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_10000_ep_1.1.1.6_discr_200

PLSP-ID: 17

Dynamic (invalid)

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Manually Provisioned SR Policy

Preference: 100 (BGP ODN) (active)

Requested BSID: dynamic

PCC info:

Symbolic name: bgp_c_10000_ep_1.1.1.6_discr_100

PLSP-ID: 16

Dynamic (pce 1.1.1.207) (valid)

Metric Type: IGP, Path Accumulated Metric: 40

16001 [Prefix-SID, 1.1.1.1]

16006 [Prefix-SID, 1.1.1.6]

Attributes:

Binding SID: 80047

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

Manually Provisioned SR Policy

Manually provisioned SR policies are configured on the head-end router. These policies can use dynamic paths or explicit paths. See the

SR-TE Policy Path Types, on page 68

section for information on manually provisioning an SR policy using dynamic or explicit paths.

PCE-Initiated SR Policy

An SR-TE policy can be configured on the path computation element (PCE) to reduce link congestion or to minimize the number of network touch points.

The PCE collects network information, such as traffic demand and link utilization. When the PCE determines that a link is congested, it identifies one or more flows that are causing the congestion. The PCE finds a suitable path and deploys an SR-TE policy to divert those flows, without moving the congestion to another part of the network. When there is no more link congestion, the policy is removed.

To minimize the number of network touch points, an application, such as a Network Services Orchestrator

(NSO), can request the PCE to create an SR-TE policy. PCE deploys the SR-TE policy using PCC-PCE communication protocol (PCEP).

For more information, see the

PCE-Initiated SR Policies, on page 123

section.

SR-TE Policy Path Types

A dynamic path is based on an optimization objective and a set of constraints. The head-end computes a solution, resulting in a SID-list or a set of SID-lists. When the topology changes, a new path is computed. If the head-end does not have enough information about the topology, the head-end might delegate the computation to a Segment Routing Path Computation Element (SR-PCE). For information on configuring SR-PCE, see

Configure Segment Routing Path Computation Element chapter.

An explicit path is a specified SID-list or set of SID-lists.

An SR-TE policy initiates a single (selected) path in RIB/FIB. This is the preferred valid candidate path.

A candidate path has the following characteristics:

• It has a preference – If two policies have same {color, endpoint} but different preferences, the policy with the highest preference is selected.

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Dynamic Paths

• It is associated with a single binding SID (BSID) – A BSID conflict occurs when there are different SR policies with the same BSID. In this case, the policy that is installed first gets the BSID and is selected.

• It is valid if it is usable.

A path is selected when the path is valid and its preference is the best among all candidate paths for that policy.

Note The protocol of the source is not relevant in the path selection logic.

Dynamic Paths

Optimization Objectives

Optimization objectives allow the head-end router to compute a SID-list that expresses the shortest dynamic path according to the selected metric type:

• IGP metric — Refer to the "Implementing IS-IS" and "Implementing OSPF" chapters in the Routing

Configuration Guide for Series Routers .

• TE metric — See the

Configure Interface TE Metrics, on page 69

section for information about configuring

TE metrics.

This example shows a dynamic path from head-end router 1 to end-point router 3 that minimizes IGP or TE metric:

• The blue path uses the minimum IGP metric: Min-Metric (1 → 3, IGP) = SID-list <16003>; cumulative

IGP metric: 20

• The green path uses the minimum TE metric: Min-Metric (1 → 3, TE) = SID-list <16005, 16004, 16003>; cumulative TE metric: 23

Configure Interface TE Metrics

Use the metric value command in SR-TE interface submode to configure the TE metric for interfaces. The value range is from 0 to 2147483647.

Segment Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 7.4.x

Configure SR-TE Policies

Constraints

Router# configure

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# interface type interface-path-id

Router(config-sr-te-if)# metric value

Configuring TE Metric: Example

The following configuration example shows how to set the TE metric for various interfaces: segment-routing traffic-eng interface TenGigE0/0/0/0 metric 100

interface TenGigE0/0/0/1 metric 1000

interface TenGigE0/0/2/0

metric 50 end

Constraints

Constraints allow the head-end router to compute a dynamic path according to the selected metric type:

• Affinity — You can apply a color or name to links or interfaces by assigning affinity bit-maps to them.

You can then specify an affinity (or relationship) between an SR policy path and link colors. SR-TE computes a path that includes or excludes links that have specific colors,or combinations of colors. See the

Named Interface Link Admin Groups and SR-TE Affinity Maps, on page 70

section for information on named interface link admin groups and SR-TE Affinity Maps.

• Disjoint — SR-TE computes a path that is disjoint from another path in the same disjoint-group. Disjoint paths do not share network resources. Path disjointness may be required for paths between the same pair of nodes, between different pairs of nodes, or a combination (only same head-end or only same end-point).

• Flexible Algorithm — Flexible Algorithm allows for user-defined algorithms where the IGP computes paths based on a user-defined combination of metric type and constraint.

Named Interface Link Admin Groups and SR-TE Affinity Maps

Named Interface Link Admin Groups and SR-TE Affinity Maps provide a simplified and more flexible means of configuring link attributes and path affinities to compute paths for SR-TE policies.

In the traditional TE scheme, links are configured with attribute-flags that are flooded with TE link-state parameters using Interior Gateway Protocols (IGPs), such as Open Shortest Path First (OSPF).

Named Interface Link Admin Groups and SR-TE Affinity Maps let you assign, or map, up to color names for affinity and attribute-flag attributes instead of 32-bit hexadecimal numbers. After mappings are defined, the attributes can be referred to by the corresponding color name in the CLI. Furthermore, you can define constraints using include-any , include-all , and exclude-any arguments, where each statement can contain up to 10 colors.

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Configure Named Interface Link Admin Groups and SR-TE Affinity Maps

Note You can configure affinity constraints using attribute flags or the Flexible Name Based Policy Constraints scheme; however, when configurations for both schemes exist, only the configuration pertaining to the new scheme is applied.

Configure Named Interface Link Admin Groups and SR-TE Affinity Maps

Use the affinity name NAME command in SR-TE interface submode to assign affinity to interfaces. Configure this on routers with interfaces that have an associated admin group attribute.

Router# configure

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# interface TenGigE0/0/1/2

Router(config-sr-if)# affinity

Router(config-sr-if-affinity)# name RED

Use the affinity-map name NAME bit-position bit-position command in SR-TE sub-mode to define affinity maps. The bit-position range is from 0 to 255.

Configure affinity maps on the following routers:

• Routers with interfaces that have an associated admin group attribute.

• Routers that act as SR-TE head-ends for SR policies that include affinity constraints.

Router# configure

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# affinity-map

Router(config-sr-te-affinity-map)# name RED bit-position 23

Configuring Link Admin Group: Example

The following example shows how to assign affinity to interfaces and to define affinity maps. This configuration is applicable to any router (SR-TE head-end or transit node) with colored interfaces.

segment-routing traffic-eng interface TenGigE0/0/1/1 affinity name CROSS

name RED

interface TenGigE0/0/1/2 affinity

name RED

interface TenGigE0/0/2/0 affinity

name BLUE

affinity-map name RED bit-position 23 name BLUE bit-position 24 name CROSS bit-position 25

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Configure SR Policy with Dynamic Path

end

Configure SR Policy with Dynamic Path

To configure a SR-TE policy with a dynamic path, optimization objectives, and affinity constraints, complete the following configurations:

Define the optimization objectives. See the

Optimization Objectives, on page 69

section.

Define the constraints. See the

Constraints, on page 70

section.

Create the policy.

Behaviors and Limitations

Examples

The following example shows a configuration of an SR policy at an SR-TE head-end router. The policy has a dynamic path with optimization objectives and affinity constraints computed by the head-end router.

segment-routing traffic-eng policy foo color 100 end-point ipv4 1.1.1.2

candidate-paths preference 100 dynamic metric type te

constraints affinity exclude-any

name RED

The following example shows a configuration of an SR policy at an SR-TE head-end router. The policy has a dynamic path with optimization objectives and affinity constraints computed by the SR-PCE.

segment-routing traffic-eng policy baa color 101 end-point ipv4 1.1.1.2

candidate-paths preference 100 dynamic pcep

metric

type te

constraints

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Explicit Paths

affinity exclude-any name BLUE

Explicit Paths

Configure SR-TE Policy with Explicit Path

To configure a SR-TE policy with an explicit path, complete the following configurations:

Create the segment lists.

Create the SR-TE policy.

Behaviors and Limitations

A segment list can use IP addresses or MPLS labels, or a combination of both.

• The IP address can be link or a Loopback address.

• Once you enter an MPLS label, you cannot enter an IP address.

When configuring an explicit path using IP addresses of links along the path, the SR-TE process selects either the protected or the unprotected Adj-SID of the link, depending on the order in which the Adj-SIDs were received.

Configure Local SR-TE Policy Using Explicit Paths

Create a segment list with IP addresses:

Router# configure

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# segment-list name SIDLIST1

Router(config-sr-te-sl)# index 10 address ipv4 1.1.1.2

Router(config-sr-te-sl)# index 20 address ipv4 1.1.1.3

Router(config-sr-te-sl)# index 30 address ipv4 1.1.1.4

Router(config-sr-te-sl)# exit

Create a segment list with MPLS labels:

Router(config-sr-te)# segment-list name SIDLIST2

Router(config-sr-te-sl)# index 10 mpls label 16002

Router(config-sr-te-sl)# index 20 mpls label 16003

Router(config-sr-te-sl)# index 30 mpls label 16004

Router(config-sr-te-sl)# exit

Create a segment list with IP addresses and MPLS labels:

Router(config-sr-te)# segment-list name SIDLIST3

Router(config-sr-te-sl)# index 10 address ipv4 1.1.1.2

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Router(config-sr-te-sl)# index 20 mpls label 16003

Router(config-sr-te-sl)# index 30 mpls label 16004

Router(config-sr-te-sl)# exit

Create the SR-TE policy:

Router(config-sr-te)# policy POLICY1

Router(config-sr-te-policy)# color 10 end-point ipv4 1.1.1.4

Router(config-sr-te-policy)# candidate-paths

Router(config-sr-te-policy-path)# preference 100

Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST1

Router(config-sr-te-pp-info)# exit

Router(config-sr-te-policy-path-pref)# exit

Router(config-sr-te-pp-info)# exit

Router(config-sr-te)# policy POLICY2

Router(config-sr-te-policy)# color 20 end-point ipv4 1.1.1.4

Router(config-sr-te-policy)# candidate-paths

Router(config-sr-te-policy-path)# preference 100

Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST2

Router(config-sr-te-pp-info)# exit

Router(config-sr-te)# policy POLICY3

Router(config-sr-te-policy)# color 30 end-point ipv4 1.1.1.4

Router(config-sr-te-policy)# candidate-paths

Router(config-sr-te-policy-path)# preference 100

Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST3

Router(config-sr-te-policy-path-pref)# commit

Running Configuration

Router# show running-configuration segment-routing traffic-eng segment-list SIDLIST1 index 10 address ipv4 1.1.1.2

index 20 address ipv4 1.1.1.3

index 30 address ipv4 1.1.1.4

segment-list SIDLIST2 index 10 mpls label 16002 index 20 mpls label 16003

index 30 mpls label 16004 segment-list SIDLIST3 index 10 address ipv4 1.1.1.2

index 20 mpls label 16003

index 30 mpls label 16004 policy POLICY1 color 10 end-point ipv4 1.1.1.4

candidate-paths preference 100 explicit segment-list SIDLIST1

policy POLICY2 color 20 end-point ipv4 1.1.1.4

candidate-paths preference 100

Configure SR-TE Policies

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Configuring Explicit Path with Affinity Constraint Validation

explicit segment-list SIDLIST2 policy POLICY3 color 30 end-point ipv4 1.1.1.4

candidate-paths

preference 100 explicit segment-list SIDLIST3

Verification

Router# show segment-routing traffic-eng policy name srte_c_20_ep_1.1.1.4

Sat Jul 8 12:25:34.114 UTC

SR-TE policy database

---------------------

Name: P1 (Color: 20, End-point: 1.1.1.4)

Status:

Admin: up Operational: up for 00:06:21 (since Jul 8 12:19:13.198)

Candidate-paths:

Preference 10:

Explicit: segment-list SIDLIST1 (active)

Weight: 2

400102 [Prefix-SID, 2.1.1.1]

400106

Explicit: segment-list SIDLIST2 (active)

Weight: 2

400222 [Prefix-SID, 22.11.1.1]

400106

Attributes:

Binding SID: 15001

Allocation mode: explicit

State: programmed

Policy selected: yes

Forward Class: 0

Configuring Explicit Path with Affinity Constraint Validation

To fully configure SR-TE flexible name-based policy constraints, you must complete these high-level tasks in order:

Assign Color Names to Numeric Values

Associate Affinity-Names with SR-TE Links

Associate Affinity Constraints for SR-TE Policies

/* Enter the global configuration mode and assign color names to numeric values

Router# configure

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# affinity-map

Router(config-sr-te-affinity-map)# blue bit-position 0

Router(config-sr-te-affinity-map)# green bit-position 1

Router(config-sr-te-affinity-map)# red bit-position 2

Router(config-sr-te-affinity-map)# exit

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Configuring Explicit Path with Affinity Constraint Validation

/* Associate affinity-names with SR-TE links

Router(config-sr-te)# interface Gi0/0/0/0

Router(config-sr-te-if)# affinity

Router(config-sr-te-if-affinity)# blue

Router(config-sr-te-if-affinity)# exit

Router(config-sr-te-if)# exit

Router(config-sr-te)# interface Gi0/0/0/1

Router(config-sr-te-if)# affinity

Router(config-sr-te-if-affinity)# blue

Router(config-sr-te-if-affinity)# green

Router(config-sr-te-if-affinity)# exit

Router(config-sr-te-if)# exit

Router(config-sr-te)#

/* Associate affinity constraints for SR-TE policies

Router(config-sr-te)# segment-list name SIDLIST1

Router(config-sr-te-sl)# index 10 address ipv4 1.1.1.2

Router(config-sr-te-sl)# index 20 address ipv4 2.2.2.23

Router(config-sr-te-sl)# index 30 address ipv4 1.1.1.4

Router(config-sr-te-sl)# exit

Router(config-sr-te)# segment-list name SIDLIST2

Router(config-sr-te-sl)# index 10 address ipv4 1.1.1.2

Router(config-sr-te-sl)# index 30 address ipv4 1.1.1.4

Router(config-sr-te-sl)# exit

Router(config-sr-te)# segment-list name SIDLIST3

Router(config-sr-te-sl)# index 10 address ipv4 1.1.1.5

Router(config-sr-te-sl)# index 30 address ipv4 1.1.1.4

Router(config-sr-te-sl)# exit

Router(config-sr-te)# policy POLICY1

Router(config-sr-te-policy)# color 20 end-point ipv4 1.1.1.4

Router(config-sr-te-policy)# binding-sid mpls 1000

Router(config-sr-te-policy)# candidate-paths

Router(config-sr-te-policy-path)# preference 200

Router(config-sr-te-policy-path-pref)# constraints affinity exclude-any red

Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST1

Router(config-sr-te-pp-info)# exit

Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST2

Router(config-sr-te-pp-info)# exit

Router(config-sr-te-policy-path-pref)# exit

Router(config-sr-te-policy-path)# preference 100

Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST3

Running Configuration

Router# show running-configuration segment-routing traffic-eng interface GigabitEthernet0/0/0/0 affinity

blue interface GigabitEthernet0/0/0/1 affinity blue green

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Protocols

segment-list name SIDLIST1 index 10 address ipv4 1.1.1.2

index 20 address ipv4 2.2.2.23

index 30 address ipv4 1.1.1.4

segment-list name SIDLIST2 index 10 address ipv4 1.1.1.2

index 30 address ipv4 1.1.1.4

segment-list name SIDLIST3

index 10 address ipv4 1.1.1.5

index 30 address ipv4 1.1.1.4

policy POLICY1 binding-sid mpls 1000 color 20 end-point ipv4 1.1.1.4

candidate-paths preference 100 explicit segment-list SIDLIST3

preference 200 explicit segment-list SIDLIST1

explicit segment-list SIDLIST2

constraints affinity exclude-any red

affinity-map blue bit-position 0 green bit-position 1 red bit-position 2

Protocols

Path Computation Element Protocol

The path computation element protocol (PCEP) describes a set of procedures by which a path computation client (PCC) can report and delegate control of head-end label switched paths (LSPs) sourced from the PCC to a PCE peer. The PCE can request the PCC to update and modify parameters of LSPs it controls. The stateful model also enables a PCC to allow the PCE to initiate computations allowing the PCE to perform network-wide orchestration.

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Configure the Head-End Router as PCEP PCC

Configure the Head-End Router as PCEP PCC

Configure the head-end router as PCEP Path Computation Client (PCC) to establish a connection to the PCE.

The PCC and PCE addresses must be routable so that TCP connection (to exchange PCEP messages) can be established between PCC and PCE.

Configure the PCC to Establish a Connection to the PCE

Use the segment-routing traffic-eng pcc command to configure the PCC source address, the SR-PCE address, and SR-PCE options.

A PCE can be given an optional precedence. If a PCC is connected to multiple PCEs, the PCC selects a PCE with the lowest precedence value. If there is a tie, a PCE with the highest IP address is chosen for computing path. The precedence value range is from 0 to 255.

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# pcc

Router(config-sr-te-pcc)# source-address ipv4 local-source-address

Router(config-sr-te-pcc)# pce address ipv4 PCE-address [ precedence value ]

Router(config-sr-te-pcc)# pce address ipv4 PCE-address [ keychain WORD ]

Configure PCEP-Related Timers

Use the timers keepalive command to specify how often keepalive messages are sent from PCC to its peers.

The range is from 0 to 255 seconds; the default value is 30.

Router(config-sr-te-pcc)# timers keepalive seconds

Use the timers deadtimer command to specify how long the remote peers wait before bringing down the

PCEP session if no PCEP messages are received from this PCC. The range is from 1 to 255 seconds; the default value is 120.

Router(config-sr-te-pcc)# timers deadtimer seconds

Use the timers delegation-timeout command to specify how long a delegated SR policy can remain up without an active connection to a PCE. The range is from 0 to 3600 seconds; the default value is 60.

Router(config-sr-te-pcc)# timers delegation-timeout seconds

PCE-Initiated SR Policy Timers

Use the timers initiated orphans command to specify the amount of time that a PCE-initiated SR policy will remain delegated to a PCE peer that is no longer reachable by the PCC. The range is from 10 to 180 seconds; the default value is 180.

Router(config-sr-te-pcc)# timers initiated orphans seconds

Use the timers initiated state command to specify the amount of time that a PCE-initiated SR policy will remain programmed while not being delegated to any PCE. The range is from 15 to 14440 seconds (24 hours); the default value is 600.

Router(config-sr-te-pcc)# timers initiated state seconds

To better understand how the PCE-initiated SR policy timers operate, consider the following example:

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Configure the Head-End Router as PCEP PCC

• PCE A instantiates SR policy P at head-end N.

• Head-end N delegates SR policy P to PCE A and programs it in forwarding.

• If head-end N detects that PCE A is no longer reachable, then head-end N starts the PCE-initiated orphan and state timers for SR policy P.

• If PCE A reconnects before the orphan timer expires, then SR policy P is automatically delegated back to its original PCE (PCE A).

• After the orphan timer expires, SR policy P will be eligible for delegation to any other surviving PCE(s).

• If SR policy P is not delegated to another PCE before the state timer expires, then head-end N will remove SR policy P from its forwarding.

Enable SR-TE SYSLOG Alarms

Use the logging policy status command to enable SR-TE related SYSLOG alarms.

Router(config-sr-te)# logging policy status

Enable PCEP Reports to SR-PCE

Use the report-all command to enable the PCC to report all SR policies in its database to the PCE.

Router(config-sr-te-pcc)# report-all

Customize MSD Value at PCC

Use the maximum-sid-depth value command to customize the Maximum SID Depth (MSD) signaled by

PCC during PCEP session establishment.

The default MSD value is equal to the maximum MSD supported by the platform ().

Router(config-sr-te)# maximum-sid-depth value

For cases with path computation at PCE, a PCC can signal its MSD to the PCE in the following ways:

• During PCEP session establishment – The signaled MSD is treated as a node-wide property.

• MSD is configured under segment-routing traffic-eng maximum-sid-depth value command

• During PCEP LSP path request – The signaled MSD is treated as an LSP property.

• On-demand (ODN) SR Policy: MSD is configured using the segment-routing traffic-eng

on-demand color color maximum-sid-depth value command

• Local SR Policy: MSD is configured using the segment-routing traffic-eng policy WORD

candidate-paths preference preference dynamic metric sid-limit value command.

Note If the configured MSD values are different, the per-LSP MSD takes precedence over the per-node MSD.

After path computation, the resulting label stack size is verified against the MSD requirement.

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Configure the Head-End Router as PCEP PCC

• If the label stack size is larger than the MSD and path computation is performed by PCE, then the PCE returns a "no path" response to the PCC.

• If the label stack size is larger than the MSD and path computation is performed by PCC, then the PCC will not install the path.

Note A sub-optimal path (if one exists) that satisfies the MSD constraint could be computed in the following cases:

• For a dynamic path with TE metric, when the PCE is configured with the pce segment-routing te-latency command or the PCC is configured with the segment-routing traffic-eng te-latency command.

• For a dynamic path with LATENCY metric

• For a dynamic path with affinity constraints

For example, if the PCC MSD is 4 and the optimal path (with an accumulated metric of 100) requires 5 labels, but a sub-optimal path exists (with accumulated metric of 110) requiring 4 labels, then the sub-optimal path is installed.

Customize the SR-TE Path Calculation

Use the te-latency command to enable ECMP-aware path computation for TE metric.

Router(config-sr-te)# te-latency

Note ECMP-aware path computation is enabled by default for IGP and LATENCY metrics.

Configure PCEP Redundancy Type

Use the redundancy pcc-centric command to enable PCC-centric high-availability model. The PCC-centric model changes the default PCC delegation behavior to the following:

• After LSP creation, LSP is automatically delegated to the PCE that computed it.

• If this PCE is disconnected, then the LSP is redelegated to another PCE.

• If the original PCE is reconnected, then the delegation fallback timer is started. When the timer expires, the LSP is redelegated back to the original PCE, even if it has worse preference than the current PCE.

Router(config-sr-te-pcc)# redundancy pcc-centric

Configuring Head-End Router as PCEP PCC and Customizing SR-TE Related Options: Example

The following example shows how to configure an SR-TE head-end router with the following functionality:

• Enable the SR-TE head-end router as a PCEP client (PCC) with 3 PCEP servers (PCE) with different precedence values. The PCE with IP address 1.1.1.57 is selected as BEST.

• Enable SR-TE related syslogs.

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BGP SR-TE

• Set the Maximum SID Depth (MSD) signaled during PCEP session establishment to 5.

• Enable PCEP reporting for all policies in the node.

segment-routing traffic-eng pcc source-address ipv4 1.1.1.2

pce address ipv4 1.1.1.57

precedence 150

password clear <password> pce address ipv4 1.1.1.58

precedence 200 password clear <password>

pce address ipv4 1.1.1.59

precedence 250

password clear <password>

logging policy status

maximum-sid-depth 5

end pcc report-all

Verification

RP/0/RSP0/CPU0:Router# show segment-routing traffic-eng pcc ipv4 peer

PCC's peer database:

--------------------

Peer address: 1.1.1.57

, Precedence: 150 , ( best PCE )

State up

Capabilities: Stateful, Update, Segment-Routing, Instantiation

Peer address: 1.1.1.58

, Precedence: 200

State up

Capabilities: Stateful, Update, Segment-Routing, Instantiation

Peer address: 1.1.1.59

, Precedence: 250

State up

Capabilities: Stateful, Update, Segment-Routing, Instantiation

BGP SR-TE

BGP may be used to distribute SR Policy candidate paths to an SR-TE head-end. Dedicated BGP SAFI and

NLRI have been defined to advertise a candidate path of an SR Policy. The advertisement of Segment Routing policies in BGP is documented in the IETF draft https://datatracker.ietf.org/doc/ draft-ietf-idr-segment-routing-te-policy/

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Configure BGP SR Policy Address Family at SR-TE Head-End

SR policies with IPv4 and IPv6 end-points can be advertised over BGPv4 or BGPv6 sessions between the

SR-TE controller and the SR-TE headend.

The Cisco IOS-XR implementation supports the following combinations:

• IPv4 SR policy advertised over BGPv4 session

• IPv6 SR policy advertised over BGPv4 session

• IPv6 SR policy advertised over BGPv6 session

Configure BGP SR Policy Address Family at SR-TE Head-End

Perform this task to configure BGP SR policy address family at SR-TE head-end:

SUMMARY STEPS

configure

router bgp as-number

bgp router-id ip-address

address-family { ipv4 | ipv6 } sr-policy

exit

neighbor ip-address

remote-as as-number

address-family { ipv4 | ipv6 } sr-policy

route-policy route-policy-name { in | out }

DETAILED STEPS

Step 1

Step 2

Command or Action configure

router bgp as-number

Example:

RP/0/RSP0/CPU0:router(config)# router bgp 65000

Purpose

Specifies the BGP AS number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

Step 3

Step 4

bgp router-id ip-address

Example:

RP/0/RSP0/CPU0:router(config-bgp)# bgp router-id

1.1.1.1

Configures the local router with a specified router ID.

address-family { ipv4 | ipv6 } sr-policy

Example:

RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 sr-policy

Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

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Configure BGP SR Policy Address Family at SR-TE Head-End

Step 5

Step 6

Step 7

Step 8

Step 9

Command or Action exit

neighbor ip-address

Example:

RP/0/RSP0/CPU0:router(config-bgp)# neighbor

10.10.0.1

Purpose

Places the router in neighbor configuration mode for BGP routing and configures the neighbor IP address as a BGP peer.

remote-as as-number

Example:

RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as

Creates a neighbor and assigns a remote autonomous system number to it.

address-family { ipv4 | ipv6 } sr-policy

Example:

RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 sr-policy

Specifies either the IPv4 or IPv6 address family and enters address family configuration submode.

route-policy route-policy-name { in | out }

Example:

RP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy pass out

Applies the specified policy to IPv4 or IPv6 unicast routes.

Example: BGP SR-TE with BGPv4 Neighbor to BGP SR-TE Controller

The following configuration shows the an SR-TE head-end with a BGPv4 session towards a BGP SR-TE controller. This BGP session is used to signal both IPv4 and IPv6 SR policies.

router bgp 65000 bgp router-id 1.1.1.1

address-family ipv4 sr-policy

address-family ipv6 sr-policy

neighbor 10.1.3.1

remote-as 10 description *** eBGP session to BGP SRTE controller ***

address-family ipv4 sr-policy route-policy pass in route-policy pass out

address-family ipv6 sr-policy

route-policy pass in route-policy pass out

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Configure SR-TE Policies

Traffic Steering

Example: BGP SR-TE with BGPv6 Neighbor to BGP SR-TE Controller

The following configuration shows an SR-TE head-end with a BGPv6 session towards a BGP SR-TE controller.

This BGP session is used to signal IPv6 SR policies.

router bgp 65000 bgp router-id 1.1.1.1

address-family ipv6 sr-policy

neighbor 3001::10:1:3:1 remote-as 10 description *** eBGP session to BGP SRTE controller *** address-family ipv6 sr-policy route-policy pass in

route-policy pass out

Traffic Steering

Automated Steering

Automated steering (AS) allows service traffic to be automatically steered onto the required transport SLA path programmed by an SR policy.

With AS, BGP automatically steers traffic onto an SR Policy based on the next-hop and color of a BGP service route. The color of a BGP service route is specified by a color extended community attribute. This color is used as a transport SLA indicator, such as min-delay or min-cost.

When the next-hop and color of a BGP service route matches the end-point and color of an SR Policy, BGP automatically installs the route resolving onto the BSID of the matching SR Policy. Recall that an SR Policy on a head-end is uniquely identified by an end-point and color.

When a BGP route has multiple extended-color communities, each with a valid SR Policy, the BGP process installs the route on the SR Policy giving preference to the color with the highest numerical value.

The granularity of AS behaviors can be applied at multiple levels, for example:

• At a service level—When traffic destined to all prefixes in a given service is associated to the same transport path type. All prefixes share the same color.

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Per-Flow Automated Steering

• At a destination/prefix level—When traffic destined to a prefix in a given service is associated to a specific transport path type. Each prefix could be assigned a different color.

• At a flow level—When flows destined to the same prefix are associated with different transport path types

AS behaviors apply regardless of the instantiation method of the SR policy, including:

• On-demand SR policy

• Manually provisioned SR policy

• PCE-initiated SR policy

Per-Flow Automated Steering

The steering of traffic through a Segment Routing (SR) policy is based on the candidate paths of that policy.

For a given policy, a candidate path specifies the path to be used to steer traffic to the policy’s destination.

The policy determines which candidate path to use based on the candidate path’s preference and state. The candidate path that is valid and has the highest preference is used to steer all traffic using the given policy.

This type of policy is called a Per-Destination Policy (PDP).

Per-Flow Automated Traffic Steering using SR-TE Policies introduces a way to steer traffic on an SR policy based on the attributes of the incoming packets, called a Per-Flow Policy (PFP).

A PFP provides up to 8 "ways" or options to the endpoint. With a PFP, packets are classified by a classification policy and marked using internal tags called forward classes (FCs). The FC setting of the packet selects the

“way”. For example, this “way” can be a traffic-engineered SR path, using a low-delay path to the endpoint.

The FC is represented as a numeral with a value of 0 to 7.

A PFP defines an array of FC-to-PDP mappings. A PFP can then be used to steer traffic into a given PDP based on the FC assigned to a packet.

As with PDPs, PFPs are identified by a {headend, color, endpoint} tuple. The color associated with a given

FC corresponds to a valid PDP policy of that color and same endpoint as the parent PFP. So PFP policies contain mappings of different FCs to valid PDP policies of different colors. Every PFP has an FC designated as its default FC. The default FC is associated to packets with a FC undefined under the PFP or for packets with a FC with no valid PDP policy.

The following example shows a per-flow policy from Node1 to Node4:

Figure 4: PFP Example

• FC=0 -> shortest path to Node4

• IGP shortest path = 16004

• FC=1 -> Min-delay path to Node4

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Per-Flow Automated Steering

• SID list = {16002,16004}

The same on-demand instantiation behaviors of PDPs apply to PFPs. For example, an edge node automatically

(on demand) instantiates Per-Flow SR Policy paths to an endpoint by service route signaling. Automated

Steering steers the service route in the matching SR Policy.

Figure 5: PFP with ODN Example

Like PDPs, PFPs have a binding SID (BSID). Existing SR-TE automated steering (AS) mechanisms for labeled traffic (via BSID) and unlabeled traffic (via BGP) onto a PFP is similar to that of a PDP. For example, a packet having the BSID of a PFP as the top label is steered onto that PFP. The classification policy on the ingress interface marks the packet with an FC based on the configured class-map. The packet is then steered to the PDP that corresponds to that FC.

Usage Guidelines and Limitations

The following guidelines and limitations apply to the platform when acting as a head-end of a PFP policy:

• BGP IPv4 unicast over PFP (steered via ODN/AS) is supported

• BGP IPv6 unicast (with IPv4 next-hop [6PE]) over PFP (steered via ODN/AS) is supported

• BGP IPv6 unicast (with IPv6 next-hop) over PFP (steered via ODN/AS) is supported

• BGP EVPN over PFP is not supported

• Pseudowire and VPLS over PFP are not supported

• BGP PIC is not supported

• When not explicitly configured, FC 0 is the default FC.

• A PFP is considered valid as long as its default FC has a valid PDP.

• The following counters are supported:

• PFP’s BSID counter (packet, bytes)

• Per-FC counters (packet, byte)

• Collected from the PDP’s segment-list-per-path egress counters

• If an SR policy is used for more than one purpose (as a regular policy as well as a PDP under one or more PFPs), then the collected counters will represent the aggregate of all contributions.

To preserve independent counters, it is recommended that an SR policy be used only for one purpose.

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Per-Flow Automated Steering

• Inbound packet classification, based on the following fields, is supported:

• IP precedence

• IP DSCP

• L3 ACL-based (L3 source/destination IP; L4 source/destination port)

• A color associated with a PFP SR policy cannot be used by a non-PFP SR policy. For example, if a per-flow ODN template for color 100 is configured, then the system will reject the configuration of any non-PFP SR policy using the same color. You must assign different color value ranges for PFP and non-PFP SR policies.

Configuring ODN Template for PFP Policies: Example

The following example depicts an ODN template for PFP policies that includes three FCs.

The example also includes the corresponding ODN templates for PDPs as follows:

• FC0 (default FC) mapped to color 10 = Min IGP path

• FC1 mapped to color 20 = Flex Algo 128 path

• FC2 mapped to color 30 = Flex Algo 129 path segment-routing traffic-eng on-demand color 10 dynamic metric type igp

on-demand color 20 dynamic sid-algorithm 128

on-demand color 30 dynamic

sid-algorithm 129

on-demand color 1000 per-flow forward-class 0 color 10 forward-class 1 color 20 forward-class 2 color 30

Manually Configuring a PFP and PDPs: Example

The following example depicts a manually defined PFP that includes three FCs and corresponding manually defined PDPs.

The example also includes the corresponding PDPs as follows:

• FC0 (default FC) mapped to color 10 = Min IGP path

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Per-Flow Automated Steering

• FC1 mapped to color 20 = Min TE path

• FC2 mapped to color 30 = Min delay path segment-routing traffic-eng policy MyPerFlow color 1000 end-point ipv4 1.1.1.4

candidate-paths preference 100 per-flow forward-class 0 color 10 forward-class 1 color 20 forward-class 2 color 30

policy MyLowIGP color 10 end-point ipv4 1.1.1.4

candidate-paths preference 100 dynamic metric type igp

policy MyLowTE color 20 end-point ipv4 1.1.1.4

candidate-paths preference 100 dynamic metric type te

policy MyLowDelay color 30 end-point ipv4 1.1.1.4

candidate-paths preference 100 dynamic metric type delay

Determining Per-Flow Policy State

A PFP is brought down for the following reasons:

• The PDP associated with the default FC is in a down state.

• All FCs are associated with PDPs in a down state.

• The FC assigned as the default FC is missing in the forward class mapping.

Scenario 1—FC 0 (default FC) is not configured in the FC mappings below: policy foo color 1 end-point ipv4 1.1.1.1

per-flow forward-class 1 color 10 forward-class 2 color 20

Scenario 2—FC 1 is configured as the default FC, however it is not present in the FC mappings: policy foo color 1 end-point ipv4 1.1.1.1

per-flow forward-class 0 color 10 forward-class 2 color 20

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Using Binding Segments forward-class default 1

Using Binding Segments

The binding segment is a local segment identifying an SR-TE policy. Each SR-TE policy is associated with a binding segment ID (BSID). The BSID is a local label that is automatically allocated for each SR-TE policy when the SR-TE policy is instantiated.

BSID can be used to steer traffic into the SR-TE policy and across domain borders, creating seamless end-to-end inter-domain SR-TE policies. Each domain controls its local SR-TE policies; local SR-TE policies can be validated and rerouted if needed, independent from the remote domain’s head-end. Using binding segments isolates the head-end from topology changes in the remote domain.

Packets received with a BSID as top label are steered into the SR-TE policy associated with the BSID. When the BSID label is popped, the SR-TE policy’s SID list is pushed.

BSID can be used in the following cases:

• Multi-Domain (inter-domain, inter-autonomous system)—BSIDs can be used to steer traffic across domain borders, creating seamless end-to-end inter-domain SR-TE policies.

• Large-Scale within a single domain—The head-end can use hierarchical SR-TE policies by nesting the end-to-end (edge-to-edge) SR-TE policy within another layer of SR-TE policies

(aggregation-to-aggregation). The SR-TE policies are nested within another layer of policies using the

BSIDs, resulting in seamless end-to-end SR-TE policies.

• Label stack compression—If the label-stack size required for an SR-TE policy exceeds the platform capability, the SR-TE policy can be seamlessly stitched to, or nested within, other SR-TE policies using a binding segment.

• BGP SR-TE Dynamic—The head-end steers the packet into a BGP-based FIB entry whose next hop is a binding-SID.

Explicit Binding SID

Use the binding-sid mpls label command in SR-TE policy configuration mode to specify the explicit BSID.

Explicit BSIDs are allocated from the segment routing local block (SRLB) or the dynamic range of labels. A best-effort is made to request and obtain the BSID for the SR-TE policy. If requested BSID is not available

(if it does not fall within the available SRLB or is already used by another application or SR-TE policy), the policy stays down.

Use the binding-sid explicit { fallback-dynamic | enforce-srlb } command to specify how the BSID allocation behaves if the BSID value is not available.

• Fallback to dynamic allocation – If the BSID is not available, the BSID is allocated dynamically and the policy comes up:

Router# configure

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# binding-sid explicit fallback-dynamic

• Strict SRLB enforcement – If the BSID is not within the SRLB, the policy stays down:

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Stitching SR-TE Polices Using Binding SID: Example

Router# configure

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# binding-sid explicit enforce-srlb

This example shows how to configure an SR policy to use an explicit BSID of 1000. If the BSID is not available, the BSID is allocated dynamically and the policy comes up.

segment-routing traffic-eng binding-sid explicit fallback-dynamic

policy goo binding-sid mpls 1000

Stitching SR-TE Polices Using Binding SID: Example

In this example, three SR-TE policies are stitched together to form a seamless end-to-end path from node 1 to node 10. The path is a chain of SR-TE policies stitched together using the binding-SIDs of intermediate policies, providing a seamless end-to-end path.

Figure 6: Stitching SR-TE Polices Using Binding SID

Step 1 On node 5, do the following: a) Define an SR-TE policy with an explicit path configured using the loopback interface IP addresses of node 9 and node 10.

b) Define an explicit binding-SID ( mpls label 15888 ) allocated from SRLB for the SR-TE policy.

Example:

Node 5 segment-routing traffic-eng segment-list PATH-9_10

index 10 address ipv4 1.1.1.9

index 20 address ipv4 1.1.1.10

policy foo binding-sid mpls 15888 color 777 end-point ipv4 1.1.1.10

candidate-paths preference 100 explicit segment-list PATH5-9_10

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Stitching SR-TE Polices Using Binding SID: Example

Step 2

RP/0/RSP0/CPU0:Node-5# show segment-routing traffic-eng policy color 777

SR-TE policy database

---------------------

Color: 777, End-point: 1.1.1.10

Name: srte_c_777_ep_1.1.1.10

Status:

Admin: up Operational: up for 00:00:52 (since Aug 19 07:40:12.662)

Candidate-paths:

Preference: 100 (configuration) (active)

Name: foo

Requested BSID: 15888

PCC info:

Symbolic name: cfg_foo_discr_100

PLSP-ID: 70

Explicit: segment-list PATH-9_10 (valid)

Weight: 1, Metric Type: TE

16009 [Prefix-SID, 1.1.1.9]

16010 [Prefix-SID, 1.1.1.10]

Attributes:

Binding SID: 15888 (SRLB)

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

On node 3, do the following: a) Define an SR-TE policy with an explicit path configured using the following:

• Loopback interface IP address of node 4

• Interface IP address of link between node 4 and node 6

• Loopback interface IP address of node 5

• Binding-SID of the SR-TE policy defined in Step 1 ( mpls label 15888 )

Note This last segment allows the stitching of these policies.

b) Define an explicit binding-SID ( mpls label 15900 ) allocated from SRLB for the SR-TE policy.

Example:

Node 3 segment-routing traffic-eng segment-list PATH-4_4-6_5_BSID index 10 address ipv4 1.1.1.4

index 20 address ipv4 10.4.6.6

index 30 address ipv4 1.1.1.5

index 40 mpls label 15888

policy baa binding-sid mpls 15900 color 777 end-point ipv4 1.1.1.5

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Stitching SR-TE Polices Using Binding SID: Example

candidate-paths preference 100 explicit segment-list PATH-4_4-6_5_BSID

RP/0/RSP0/CPU0:Node-3# show segment-routing traffic-eng policy color 777

SR-TE policy database

---------------------

Color: 777, End-point: 1.1.1.5

Name: srte_c_777_ep_1.1.1.5

Status:

Admin: up Operational: up for 00:00:32 (since Aug 19 07:40:32.662)

Candidate-paths:

Preference: 100 (configuration) (active)

Name: baa

Requested BSID: 15900

PCC info:

Symbolic name: cfg_baa_discr_100

PLSP-ID: 70

Explicit: segment-list PATH-4_4-6_5_BSID (valid)

Weight: 1, Metric Type: TE

16004 [Prefix-SID, 1.1.1.4]

80005 [Adjacency-SID, 10.4.6.4 - 10.4.6.6]

16005 [Prefix-SID, 1.1.1.5]

15888

Attributes:

Binding SID: 15900 (SRLB)

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

Step 3 On node 1, define an SR-TE policy with an explicit path configured using the loopback interface IP address of node 3 and the binding-SID of the SR-TE policy defined in step 2 ( mpls label 15900 ). This last segment allows the stitching of these policies.

Example:

Node 1 segment-routing traffic-eng segment-list PATH-3_BSID index 10 address ipv4 1.1.1.3

index 20 mpls label 15900

policy bar color 777 end-point ipv4 1.1.1.3

candidate-paths preference 100

explicit segment-list PATH-3_BSID

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L2VPN Preferred Path

RP/0/RSP0/CPU0:Node-1# show segment-routing traffic-eng policy color 777

SR-TE policy database

---------------------

Color: 777, End-point: 1.1.1.3

Name: srte_c_777_ep_1.1.1.3

Status:

Admin: up Operational: up for 00:00:12 (since Aug 19 07:40:52.662)

Candidate-paths:

Preference: 100 (configuration) (active)

Name: bar

Requested BSID: dynamic

PCC info:

Symbolic name: cfg_bar_discr_100

PLSP-ID: 70

Explicit: segment-list PATH-3_BSID (valid)

Weight: 1, Metric Type: TE

16003 [Prefix-SID, 1.1.1.3]

15900

Attributes:

Binding SID: 80021

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

L2VPN Preferred Path

EVPN VPWS Preferred Path over SR-TE Policy feature allows you to set the preferred path between the two end-points for EVPN VPWS pseudowire (PW) using SR-TE policy.

L2VPN VPLS or VPWS Preferred Path over SR-TE Policy feature allows you to set the preferred path between the two end-points for L2VPN Virtual Private LAN Service (VPLS) or Virtual Private Wire Service (VPWS) using SR-TE policy.

Refer to the EVPN VPWS Preferred Path over SR-TE Policy and L2VPN VPLS or VPWS Preferred Path over SR-TE Policy sections in the "L2VPN Services over Segment Routing for Traffic Engineering Policy" chapter of the L2VPN and Ethernet Services Configuration Guide .

Policy-Based Tunnel Selection for SR-TE Policy

Policy-Based Tunnel Selection (PBTS) is a mechanism that lets you direct traffic into specific SR-TE policies based on different classification criteria. PBTS benefits Internet service providers (ISPs) that carry voice and data traffic through their networks, who want to route this traffic to provide optimized voice service.

PBTS works by selecting SR-TE policies based on the classification criteria of the incoming packets, which are based on the IP precedence, experimental (EXP), differentiated services code point (DSCP), or type of service (ToS) field in the packet. Default-class configured for paths is always zero (0). If there is no TE for a given forward-class, then the default-class (0) will be tried. If there is no default-class, then the packet is dropped. PBTS supports up to seven (exp 1 - 7) EXP values associated with a single SR-TE policy.

For more information about PBTS, refer to the "Policy-Based Tunnel Selection" section in the MPLS

Configuration Guide for Cisco NCS 6000 Series Routers .

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Policy-Based Tunnel Selection for SR-TE Policy

Configure Policy-Based Tunnel Selection for SR-TE Policies

The following section lists the steps to configure PBTS for an SR-TE policy.

Note Steps 1 through 4 are detailed in the "Implementing MPLS Traffic Engineering" chapter of the MPLS

Configuration Guide for Cisco NCS 6000 Series Routers .

Define a class-map based on a classification criteria.

Define a policy-map by creating rules for the classified traffic.

Associate a forward-class to each type of ingress traffic.

Enable PBTS on the ingress interface, by applying this service-policy.

Create one or more egress SR-TE policies (to carry packets based on priority) to the destination and associate the egress SR-TE policy to a forward-class.

Configuration Example

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# policy POLICY-PBTS

Router(config-sr-te-policy)# color 1001 end-point ipv4 1.1.1.20

Router(config-sr-te-policy)# autoroute

Router(config-sr-te-policy-autoroute)# include all

Router(config-sr-te-policy-autoroute)# forward-class 1

Router(config-sr-te-policy-autoroute)# exit

Router(config-sr-te-policy)# candidate-paths

Router(config-sr-te-policy-path)# preference 1

Router(config-sr-te-policy-path-pref)# explicit segment-list SIDLIST1

Router(config-sr-te-policy-path-pref)# exit

Router(config-sr-te-pp-info)# exit

Router(config-sr-te-policy-path-pref)# exit

Router(config-sr-te-policy-path)# preference 2

Router(config-sr-te-policy-path-pref)# dynamic

Router(config-sr-te-pp-info)# metric

Router(config-sr-te-path-metric)# type te

Router(config-sr-te-path-metric)# commit

Running Configuration segment-routing traffic-eng policy POLICY-PBTS color 1001 end-point ipv4 1.1.1.20

autoroute include all forward-class 1

candidate-paths preference 1 explicit segment-list SIDLIST1

preference 2 dynamic metric

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Miscellaneous type te

Miscellaneous

LDP over Segment Routing Policy

The LDP over Segment Routing Policy feature enables an LDP-targeted adjacency over a Segment Routing

(SR) policy between two routers. This feature extends the existing MPLS LDP address family neighbor configuration to specify an SR policy as the targeted end-point.

LDP over SR policy is supported for locally configured SR policies with IPv4 end-points.

For more information about MPLS LDP, see the "Implementing MPLS Label Distribution Protocol" chapter in the MPLS Configuration Guide .

For more information about Autoroute, see the Autoroute Announce for SR-TE section.

Note Before you configure an LDP targeted adjacency over SR policy name, you need to create the SR policy under

Segment Routing configuration. The SR policy interface names are created internally based on the color and endpoint of the policy. LDP is non-operational if SR policy name is unknown.

The following functionality applies:

Configure the SR policy – LDP receives the associated end-point address from the interface manager (IM) and stores it in the LDP interface database (IDB) for the configured SR policy.

Configure the SR policy name under LDP – LDP retrieves the stored end-point address from the IDB and uses it. Use the auto-generated SR policy name assigned by the router when creating an LDP targeted adjacency over an SR policy. Auto-generated SR policy names use the following naming convention:

srte_c_color_val_ep_endpoint-address . For example, srte_c_1000_ep_1.1.1.2

Configuration Example

/* Enter the SR-TE configuration mode and create the SR policy. This example corresponds to a local SR policy with an explicit path. */

Router(config)# segment-routing

Router(config-sr)# traffic-eng

Router(config-sr-te)# segment-list sample-sid-list

Router(config-sr-te-sl)# index 10 address ipv4 1.1.1.7

Router(config-sr-te-sl)# index 20 address ipv4 1.1.1.2

Router(config-sr-te-sl)# exit

Router(config-sr-te)# policy sample_policy

Router(config-sr-te-policy)# color 1000 end-point ipv4 1.1.1.2

Router(config-sr-te-policy)# candidate-paths

Router(config-sr-te-policy-path)# preference 100

Router(config-sr-te-policy-path-pref)# explicit segment-list sample-sid-list

Router(config-sr-te-pp-info)# end

/* Configure LDP over an SR policy */

Router(config)# mpls ldp

Router(config-ldp)# address-family ipv4

Router(config-ldp-af)# neighbor sr-policy srte_c_1000_ep_1.1.1.2 targeted

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LDP over Segment Routing Policy

Router(config-ldp-af)#

Note Do one of the following to configure LDP discovery for targeted hellos:

• Active targeted hellos (SR policy head end): mpls ldp interface GigabitEthernet0/0/0/0

• Passive targeted hellos (SR policy end-point): mpls ldp address-family ipv4 discovery targeted-hello accept

Running Configuration segment-routing traffic-eng segment-list sample-sid-list index 10 address ipv4 1.1.1.7

index 20 address ipv4 1.1.1.2

policy sample_policy color 1000 end-point ipv4 1.1.1.2

candidate-paths preference 100

explicit segment-list sample-sid-list

mpls ldp address-family ipv4 neighbor sr-policy srte_c_1000_ep_1.1.1.2 targeted discovery targeted-hello accept

Verification

Router# show mpls ldp interface brief

Interface VRF Name Config Enabled IGP-Auto-Cfg TE-Mesh-Grp cfg

--------------- ------------------- ------ ------- ------------ ---------------

Te0/3/0/0/3 default Y Y 0 N/A

Te0/3/0/0/6 default Y Y 0 N/A

Te0/3/0/0/7

Te0/3/0/0/8

Te0/3/0/0/9 srte_c_1000_ default default default default

N/A

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LDP over Segment Routing Policy

Router# show mpls ldp interface

Interface TenGigE0/3/0/0/3 (0xa000340)

VRF: 'default' (0x60000000)

Enabled via config: LDP interface

Interface TenGigE0/3/0/0/6 (0xa000400)

VRF: 'default' (0x60000000)

Enabled via config: LDP interface

Interface TenGigE0/3/0/0/7 (0xa000440)

VRF: 'default' (0x60000000)

Enabled via config: LDP interface

Interface TenGigE0/3/0/0/8 (0xa000480)

VRF: 'default' (0x60000000)

Disabled:

Interface TenGigE0/3/0/0/9 (0xa0004c0)

VRF: 'default' (0x60000000)

Disabled:

Interface srte_c_1000_ep_1.1.1.2 (0x520)

VRF: 'default' (0x60000000)

Enabled via config: LDP interface

Router# show segment-routing traffic-eng policy color 1000

SR-TE policy database

---------------------

Color: 1000, End-point: 1.1.1.2

Name: srte_c_1000_ep_1.1.1.2

Status:

Admin: up Operational: up for 00:02:00 (since Jul 2 22:39:06.663)

Candidate-paths:

Preference: 100 (configuration) (active)

Name: sample_policy

Requested BSID: dynamic

PCC info:

Symbolic name: cfg_sample_policy_discr_100

PLSP-ID: 17

Explicit: segment-list sample-sid-list (valid)

Weight: 1, Metric Type: TE

16007 [Prefix-SID, 1.1.1.7]

16002 [Prefix-SID, 1.1.1.2]

Attributes:

Binding SID: 80011

Forward Class: 0

Steering BGP disabled: no

IPv6 caps enable: yes

Router# show mpls ldp neighbor 1.1.1.2 detail

Peer LDP Identifier: 1.1.1.2:0

TCP connection: 1.1.1.2:646 - 1.1.1.6:57473

Graceful Restart: No

Session Holdtime: 180 sec

State: Oper; Msgs sent/rcvd: 421/423; Downstream-Unsolicited

Up time: 05:22:02

LDP Discovery Sources:

IPv4: (1)

Targeted Hello (1.1.1.6 -> 1.1.1.2, active/passive)

IPv6: (0)

Addresses bound to this peer:

IPv4: (9)

1.1.1.2

10.2.4.2

2.2.2.99

10.2.22.2

10.1.2.2

10.2.222.2

10.2.3.2

10.30.110.132

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Configure Seamless Bidirectional Forwarding Detection

11.2.9.2

IPv6: (0)

Peer holdtime: 180 sec; KA interval: 60 sec; Peer state: Estab

NSR: Disabled

Clients: LDP over SR Policy

Capabilities:

Sent:

0x508 (MP: Point-to-Multipoint (P2MP))

0x509 (MP: Multipoint-to-Multipoint (MP2MP))

0x50a (MP: Make-Before-Break (MBB))

0x50b (Typed Wildcard FEC)

Received:

0x508 (MP: Point-to-Multipoint (P2MP))

0x509 (MP: Multipoint-to-Multipoint (MP2MP))

0x50a (MP: Make-Before-Break (MBB))

0x50b (Typed Wildcard FEC)

Configure Seamless Bidirectional Forwarding Detection

Bidirectional forwarding detection (BFD) provides low-overhead, short-duration detection of failures in the path between adjacent forwarding engines. BFD allows a single mechanism to be used for failure detection over any media and at any protocol layer, with a wide range of detection times and overhead. The fast detection of failures provides immediate reaction to failure in the event of a failed link or neighbor.

In BFD, each end of the connection maintains a BFD state and transmits packets periodically over a forwarding path. Seamless BFD (SBFD) is unidirectional, resulting in faster session activation than BFD. The BFD state and client context is maintained on the head-end (initiator) only. The tail-end (reflector) validates the BFD packet and responds, so there is no need to maintain the BFD state on the tail-end.

Initiators and Reflectors

SBFD runs in an asymmetric behavior, using initiators and reflectors.

The following figure represents the roles of the SBFD initiator and reflector.

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Figure 7: SBFD Initiator and Reflector

Configure the SBFD Reflector

The initiator is an SBFD session on a network node that performs a continuity test to a remote entity by sending

SBFD packets. The initiator injects the SBFD packets into the segment-routing traffic-engineering (SRTE) policy. The initiator triggers the SBFD session and maintains the BFD state and client context.

The reflector is an SBFD session on a network node that listens for incoming SBFD control packets to local entities and generates response SBFD control packets. The reflector is stateless and only reflects the SBFD packets back to the initiator.

A node can be both an initiator and a reflector, if you want to configure different SBFD sessions.

For SR-TE, SBFD control packets are label switched in forward and reverse direction. For SBFD, the tail-end node is the reflector node; other nodes cannot be a reflector. When using SBFD with SR-TE, if the forward and return directions are label-switched paths, SBFD need not be configured on the reflector node.

Discriminators

The BFD control packet carries 32-bit discriminators (local and remote) to demultiplex BFD sessions. SBFD requires globally unique SBFD discriminators that are known by the initiator.

The SBFD control packets contain the discriminator of the initiator, which is created dynamically, and the discriminator of the reflector, which is configured as a local discriminator on the reflector.

Configure the SBFD Reflector

To ensure the SBFD packet arrives on the intended reflector, each reflector has at least one globally unique discriminator. Globally unique discriminators of the reflector are known by the initiator before the session starts. An SBFD reflector only accepts BFD control packets where "Your Discriminator" is the reflector discriminator.

This task explains how to configure local discriminators on the reflector.

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Configure the SBFD Reflector

Before you begin

Enable mpls oam on the reflector to install a routing information base (RIB) entry for 127.0.0.0/8.

Router_5# configure

Router_5(config)# mpls oam

Router_5(config-oam)#

SUMMARY STEPS

configure

sbfd

local-discriminator { ipv4-address | 32-bit-value | dynamic | interface interface }

commit

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure sbfd

Example:

Router_5(config)# sbfd

Purpose

Enters XR Config mode.

Enters SBFD configuration mode.

Step 3 local-discriminator { ipv4-address | 32-bit-value | dynamic | interface interface }

Example:

Router_5(config-sbfd)# local-discriminator 1.1.1.5

Router_5(config-sbfd)# local-discriminator

987654321

Router_5(config-sbfd)# local-discriminator dynamic

Router_5(config-sbfd)# local-discriminator interface Loopback0

Configures the local discriminator. You can configure multiple local discriminators.

Step 4 commit

Verify the local discriminator configuration.

Example

Router_5# show bfd target-identifier local

100

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Configure the SBFD Initiator

Local Target Identifier Table

-----------------------------

Discr

-----

16843013

Discr Src VRF

Name

Status Flags

---------------------- --------

Local default enable ----ia -

987654321 Local

2147483649 Local default enable ---v --default enable ------d

Legend: TID - Target Identifier a - IP Address mode d - Dynamic mode i - Interface mode v - Explicit Value mode

What to do next

Configure the SBFD initiator.

Configure the SBFD Initiator

Perform the following configurations on the SBFD initiator.

Enable Line Cards to Host BFD Sessions

The SBFD initiator sessions are hosted by the line card CPU.

This task explains how to enable line cards to host BFD sessions.

SUMMARY STEPS

configure

bfd

multipath include location node-id

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure bfd

Example:

Router_1(config)# bfd

Purpose

Enters XR Config mode.

Enters BFD configuration mode.

Step 3 multipath include location node-id

Example:

Router_1(config-bfd)# multipath include location

Configures BFD multiple path on specific line card. Any of the configured line cards can be instructed to host a BFD session.

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Map a Destination Address to a Remote Discriminator

Command or Action

0/1/CPU0

Router_1(config-bfd)# multipath include location

0/2/CPU0

Router_1(config-bfd)# multipath include location

0/3/CPU0

Purpose

What to do next

Map a destination address to a remote discriminator.

Map a Destination Address to a Remote Discriminator

The SBFD initiator uses a Remote Target Identifier (RTI) table to map a destination address (Target ID) to a remote discriminator.

This task explains how to map a destination address to a remote discriminator.

SUMMARY STEPS

configure

sbfd

remote-target ipv4 ipv4-address

remote-discriminator remote-discriminator

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure sbfd

Example:

Router_1(config)# sbfd

Purpose

Enters XR Config mode.

Enters SBFD configuration mode.

Step 3

Step 4

remote-target ipv4 ipv4-address

Example:

Router_1(config-sbfd)# remote-target ipv4 1.1.1.5

Configures the remote target.

remote-discriminator remote-discriminator

Example:

Router_1(config-sbfd-nnnn)# remote-discriminator

Maps the destination address (Target ID) to a remote discriminator.

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Enable Seamless BFD Under an SR-TE Policy or SR-ODN Color Template

Command or Action

16843013

Purpose

Verify the remote discriminator configuration.

Example

Router_1# show bfd target-identifier remote

Remote Target Identifier Table

------------------------------

Discr Discr Src VRF

------

16843013

Target ID Name

---------------

Remote default

1.1.1.5

Legend: TID - Target Identifier

TID Type Status

------------ipv4 enable

What to do next

Enable SBFD on an SR-TE policy.

Enable Seamless BFD Under an SR-TE Policy or SR-ODN Color Template

This example shows how to enable SBFD on an SR-TE policy or an SR on-demand (SR-ODN) color template.

Note Do not use BFD with disjoint paths. The reverse path might not be disjoint, causing a single link failure to bring down BFD sessions on both the disjoint paths.

Enable BFD

• Use the bfd command in SR-TE policy configuration mode to enable BFD and enters BFD configuration mode.

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# policy POLICY1

Router(config-sr-te-policy)# bfd

Router(config-sr-te-policy-bfd)#

Use the bfd command in SR-ODN configuration mode to enable BFD and enters BFD configuration mode.

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# on-demand color 10

Router(config-sr-te-color)# bfd

Router(config-sr-te-color-bfd)#

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Enable Seamless BFD Under an SR-TE Policy or SR-ODN Color Template

Configure BFD Options

• Use the minimum-interval milliseconds command to set the interval between sending BFD hello packets to the neighbor. The range is from 15 to 200. The default is 15.

Router(config-sr-te-policy-bfd)# minimum-interval 50

• Use the multiplier multiplier command to set the number of times a packet is missed before BFD declares the neighbor down. The range is from 2 to 10. The default is 3.

Router(config-sr-te-policy-bfd)# multiplier 2

• Use the invalidation-action { down | none } command to set the action to be taken when BFD session is invalidated.

• down : LSP can only be operationally up if the BFD session is up

• none : BFD session state does not affect LSP state, use for diagnostic purposes

Router(config-sr-te-policy-bfd)# invalidation-action down

• ( SR-TE policy only ) Use the reverse-path binding-label label command to specify BFD packets return to head-end by using a binding label.

By default, the S-BFD return path (from tail-end to head-end) is via IPv4. You can use a reverse binding label so that the packet arrives at the tail-end with the reverse binding label as the top label. This label is meant to point to a policy that will take the BFD packets back to the head-end. The reverse binding label is configured per-policy.

Note that when MPLS return path is used, BFD uses echo mode packets, which means the tail-end’s

BFD reflector does not process BFD packets at all.

The MPLS label value at the tail-end and the head-end must be synchronized by the operator or controller.

Because the tail-end binding label should remain constant, configure it as an explicit BSID, rather than dynamically allocated.

Router(config-sr-te-policy-bfd)# reverse-path binding-label 24036

• Use the logging session-state-change command to log when the state of the session changes

Router(config-sr-te-policy-bfd)# logging session-state-change

Examples

This example shows how to enable SBFD on an SR-TE policy.

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# policy POLICY1

Router(config-sr-te-policy)# bfd

Router(config-sr-te-policy-bfd)# invalidation-action down

Router(config-sr-te-policy-bfd)# minimum-interval 50

Router(config-sr-te-policy-bfd)# multiplier 2

Router(config-sr-te-policy-bfd)# reverse-path binding-label 24036

Router(config-sr-te-policy-bfd)# logging session-state-change segment-routing

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SR-TE Reoptimization Timers traffic-eng policy POLICY1 bfd minimum-interval 50 multiplier 2 invalidation-action down reverse-path

binding-label 24036

logging session-state-change

This example shows how to enable SBFD on an SR-ODN color.

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# on-demand color 10

Router(config-sr-te-color)# bfd

Router(config-sr-te-color-bfd)# minimum-interval 50

Router(config-sr-te-color-bfd)# multiplier 2

Router(config-sr-te-color-bfd)# logging session-state-change

Router(config-sr-te-color-bfd)# invalidation-action down segment-routing traffic-eng on-demand color 10 bfd minimum-interval 50 multiplier 2 invalidation-action down logging

session-state-change

SR-TE Reoptimization Timers

SR-TE path re-optimization occurs when the head-end determines that there is a more optimal path available than the one currently used. For example, in case of a failure along the SR-TE LSP path, the head-end could detect and revert to a more optimal path by triggering re-optimization.

Re-optimization can occur due to the following events:

• The explicit path hops used by the primary SR-TE LSP explicit path are modified

• The head-end determines the currently used path-option are invalid due to either a topology path disconnect, or a missing SID in the SID database that is specified in the explicit-path

• A more favorable path-option (lower index) becomes available

For event-based re-optimization, you can specify various delay timers for path re-optimization. For example, you can specify how long to wait before switching to a reoptimized path

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SR-TE Reoptimization Timers

Additionally, you can configure a timer to specify how often to perform reoptimization of policies. You can also trigger an immediate reoptimization for a specific policy or for all policies.

SR-TE Reoptimization

To trigger an immediate SR-TE reoptimization, use the segment-routing traffic-eng reoptimization command in Exec mode:

Router# segment-routing traffic-eng reoptimization { all | name policy }

Use the all option to trigger an immediate reoptimization for all policies. Use the name policy option to trigger an immediate reoptimization for a specific policy.

Configuring SR-TE Reoptimization Timers

Use these commands in SR-TE configuration mode to configure SR-TE reoptimization timers:

• timers candidate-path cleanup-delay seconds —Specifies the delay before cleaning up candidate paths, in seconds. The range is from 0 (immediate clean-up) to 86400; the default value is 120

• timers cleanup-delay seconds —Specifies the delay before cleaning up previous path, in seconds. The range is from 0 (immediate clean-up) to 300; the default value is 10.

• timers init-verify-restart seconds —Specifies the delay for topology convergence after the topology starts populating due to a restart, in seconds. The range is from 10 to 10000; the default is 40.

• timers init-verify-startup seconds —Specifies the delay for topology convergence after topology starts populating for due to startup, in seconds. The range is from 10 to 10000; the default is 300

• timers init-verify-switchover seconds —Specifies the delay for topology convergence after topology starts populating due to a switchover, in seconds. The range is from 10 to 10000; the default is 60.

• timers install-delay seconds —Specifies the delay before switching to a reoptimized path, in seconds.

The range is from 0 (immediate installation of new path) to 300; the default is 10.

• timers periodic-reoptimization seconds —Specifies how often to perform periodic reoptimization of policies, in seconds. The range is from 0 to 86400; the default is 600.

Example Configuration

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# timers

Router(config-sr-te-timers)# candidate-path cleanup-delay 600

Router(config-sr-te-timers)# cleanup-delay 60

Router(config-sr-te-timers)# init-verify-restart 120

Router(config-sr-te-timers)# init-verify-startup 600

Router(config-sr-te-timers)# init-verify-switchover 30

Router(config-sr-te-timers)# install-delay 60

Router(config-sr-te-timers)# periodic-reoptimization 3000

Running Config segment-routing traffic-eng timers install-delay 60 periodic-reoptimization 3000 cleanup-delay 60

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candidate-path cleanup-delay 600 init-verify-restart 120 init-verify-startup 600 init-verify-switchover 30

SR-TE Reoptimization Timers

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Enabling Segment Routing Flexible Algorithm

Segment Routing Flexible Algorithm allows operators to customize IGP shortest path computation according to their own needs. An operator can assign custom SR prefix-SIDs to realize forwarding beyond link-cost-based

SPF. As a result, Flexible Algorithm provides a traffic engineered path automatically computed by the IGP to any destination reachable by the IGP.

The SR architecture associates prefix-SIDs to an algorithm which defines how the path is computed. Flexible

Algorithm allows for user-defined algorithms where the IGP computes paths based on a user-defined combination of metric type and constraint.

This document describes the IS-IS extension to support Segment Routing Flexible Algorithm on an MPLS data-plane.

•

Prerequisites for Flexible Algorithm, on page 109

•

Building Blocks of Segment Routing Flexible Algorithm, on page 109

•

Configuring Flexible Algorithm, on page 111

•

Example: Configuring IS-IS Flexible Algorithm, on page 113

•

Example: Traffic Steering to Flexible Algorithm Paths, on page 113

Prerequisites for Flexible Algorithm

Segment routing must be enabled on the router before the Flexible Algorithm functionality is activated.

Building Blocks of Segment Routing Flexible Algorithm

This section describes the building blocks that are required to support the SR Flexible Algorithm functionality in IS-IS .

Flexible Algorithm Definition

Many possible constraints may be used to compute a path over a network. Some networks are deployed with multiple planes. A simple form of constraint may be to use a particular plane. A more sophisticated form of constraint can include some extended metric, like delay, as described in [RFC7810]. Even more advanced case could be to restrict the path and avoid links with certain affinities. Combinations of these are also possible.

To provide a maximum flexibility, the mapping between the algorithm value and its meaning can be defined by the user. When all the routers in the domain have the common understanding what the particular algorithm

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Flexible Algorithm Membership value represents, the computation for such algorithm is consistent and the traffic is not subject to looping.

Here, since the meaning of the algorithm is not defined by any standard, but is defined by the user, it is called a Flexible Algorithm.

Flexible Algorithm Membership

An algorithm defines how the best path is computed by IGP. Routers advertise the support for the algorithm as a node capability. Prefix-SIDs are also advertised with an algorithm value and are tightly coupled with the algorithm itself.

An algorithm is a one octet value. Values from 128 to 255 are reserved for user defined values and are used for Flexible Algorithm representation.

Flexible Algorithm Definition Advertisement

To guarantee the loop free forwarding for paths computed for a particular Flexible Algorithm, all routers in the network must share the same definition of the Flexible Algorithm. This is achieved by dedicated router(s) advertising the definition of each Flexible Algorithm. Such advertisement is associated with the priority to make sure that all routers will agree on a single and consistent definition for each Flexible Algorithm.

Definition of Flexible Algorithm includes:

• Metric type

• Affinity constraints

To enable the router to advertise the definition for the particular Flexible Algorithm, advertise-definition command is used. At least one router in the area, preferably two for redundancy, must advertise the Flexible

Algorithm definition. Without the valid definition being advertised, the Flexible Algorithm will not be functional.

Flexible Algorithm Prefix-SID Advertisement

To be able to forward traffic on a Flexible Algorithm specific path, all routers participating in the Flexible

Algorithm will install a MPLS labeled path for the Flexible Algorithm specific SID that is advertised for the prefix. Only prefixes for which the Flexible Algorithm specific Prefix-SID is advertised is subject to Flexible

Algorithm specific forwarding.

Calculation of Flexible Algorithm Path

A router may compute path for multiple Flexible Algorithms. A router must be configured to support particular

Flexible Algorithm before it can compute any path for such Flexible Algorithm. A router must have a valid definition of the Flexible Algorithm before Flexible Algorithm is used.

When computing the shortest path tree for particular Flexible Algorithm:

• All nodes that don't advertise support for Flexible Algorithm are pruned from the topology.

• If the Flexible Algorithm definition includes affinities that are excluded, then all links for which any of such affinities are advertised will be pruned from the topology.

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Installation of Forwarding Entries for Flexible Algorithm Paths

• Router uses the metric that is part of the Flexible Algorithm definition. If the metric isn't advertised for the particular link, the link is pruned from the topology.

Configuring Microloop Avoidance for Flexible Algorithm

By default, Microloop Avoidance per Flexible Algorithm instance follows Microloop Avoidance configuration for algo-0. For information about configuring Microloop Avoidance, see

Configure Segment Routing Microloop

Avoidance, on page 147 .

You can disable Microloop Avoidance for Flexible Algorithm using the following commands:

router isis instance flex-algo algo microloop avoidance disable

router ospf process flex-algo algo microloop avoidance disable

Configuring LFA / TI-LFA for Flexible Algorithm

By default, LFA/TI-LFA per Flexible Algorithm instance follows LFA/TI-LFA configuration for algo-0. For information about configuring TI-LFA, see

Configure Topology-Independent Loop-Free Alternate (TI-LFA), on page 141

You can disable TI-LFA for Flexible Algorithm using the following commands:

router isis instance flex-algo algo fast-reroute disable

router ospf process flex-algo algo fast-reroute disable

Installation of Forwarding Entries for Flexible Algorithm Paths

Flexible Algorithm path to any prefix must be installed in the forwarding using the Prefix-SID that was advertised for such Flexible Algorithm. If the Prefix-SID for Flexible Algorithm is not known, such Flexible

Algorithm path is not installed in forwarding for such prefix..

Only MPLS to MPLS entries are installed for a Flexible Algorithm path. No IP to IP or IP to MPLS entries are installed. These follow the native IPG paths computed based on the default algorithm and regular IGP metrics.

Configuring Flexible Algorithm

The following ISIS configuration sub-mode is used to configure Flexible Algorithm:

router isis instance flex-algo algo

router ospf process flex-algo algo algo —value from 128 to 255

Configuring Flexible Algorithm Definitions

The following commands are used to configure Flexible Algorithm definition under the flex-algo sub-mode:

• metric-type delay

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Configuring Flexible Algorithm

Note By default the regular IGP metric is used. If delay metric is enabled, the advertised delay on the link is used as a metric for Flexible Algorithm computation.

• affinity exclude-any name1, name2, … name —name of the affinity map

•

priority priority value priority value —priority used during the Flexible Algorithm definition election.

The following command is used to enable advertisement of the Flexible Algorithm definition in IS-IS:

router isis instance flex-algo algo advertise-definition

Configuring Affinity

The following command is used for defining the affinity-map. Affinity-map associates the name with the particular bit positions in the Extended Admin Group bitmask.

router isis instance flex-algo algo affinity-map name bit-position bit number

router ospf process flex-algo algo affinity-map name bit-position bit number

• name —name of the affinity-map.

• bit number —bit position in the Extended Admin Group bitmask.

The following command is used to associate the affinity with an interface:

router isis instance interface type interface-path-id affinity flex-algo name 1, name 2, …

router ospf process area area interface type interface-path-id affinity flex-algo name 1, name 2, … name —name of the affinity-map

Configuring Prefix-SID Advertisement

The following command is used to advertise prefix-SID for default and strict-SPF algorithm:

router isis instance interface type interface-path-id address-family { ipv4 | ipv6 } [ unicast ] prefix-sid [ strict-spf | algorithm algorithm-number ] [ index | absolute ] sid value

router ospf process area area interface Loopback interface-instance prefix-sid [ strict-spf

| algorithm algorithm-number ] [ index | absolute ] sid value

• algorithm-number —Flexible Algorithm number

• sid value —SID value

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Example: Configuring IS-IS Flexible Algorithm

Example: Configuring IS-IS Flexible Algorithm

router isis 1 affinity-map red bit-position 65 affinity-map blue bit-position 8 affinity-map green bit-position 201 flex-algo 128 advertise-definition affinity exclude-any red

affinity include-any blue flex-algo 129

affinity exclude-any green

address-family ipv4 unicast segment-routing mpls

interface Loopback0

address-family ipv4 unicast prefix-sid algorithm 128 index 100 prefix-sid algorithm 129 index 101 interface GigabitEthernet0/0/0/0 affinity flex-algo red

interface GigabitEthernet0/0/0/1 affinity flex-algo blue red

interface GigabitEthernet0/0/0/2 affinity flex-algo blue

Example: Traffic Steering to Flexible Algorithm Paths

BGP Routes on PE – Color Based Steering

SR-TE On Demand Next-Hop (ODN) feature can be used to steer the BGP traffic towards the Flexible

Algorithm paths.

The following example configuration shows how to setup BGP steering local policy, assuming two router:

R1 (2.2.2.2) and R2 (4.4.4.4), in the topology.

Configuration on router R1: vrf Test address-family ipv4 unicast import route-target

1:150

export route-policy SET_COLOR_RED_HI_BW export route-target

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BGP Routes on PE – Color Based Steering

interface Loopback0 ipv4 address 2.2.2.2 255.255.255.255

interface Loopback150 vrf Test ipv4 address 2.2.2.222 255.255.255.255

interface TenGigE0/1/0/3/0 description exr1 to cxr1 ipv4 address 10.0.20.2 255.255.255.0

extcommunity-set opaque color129-red-igp

129 end-set

route-policy PASS pass end-policy

route-policy SET_COLOR_RED_HI_BW set extcommunity color color129-red-igp pass end-policy

router isis 1 is-type level-2-only net 49.0001.0000.0000.0002.00

log adjacency changes affinity-map RED bit-position 28 flex-algo 128 priority 228

address-family ipv4 unicast metric-style wide advertise link attributes router-id 2.2.2.2

segment-routing mpls

interface Loopback0 address-family ipv4 unicast prefix-sid index 2

prefix-sid algorithm 128 index 282

interface TenGigE0/1/0/3/0 point-to-point address-family ipv4 unicast

router bgp 65000 bgp router-id 2.2.2.2

address-family ipv4 unicast

address-family vpnv4 unicast retain route-target all

neighbor-group RR-services-group remote-as 65000 update-source Loopback0 address-family ipv4 unicast

address-family vpnv4 unicast

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BGP Routes on PE – Color Based Steering

neighbor 4.4.4.4

use neighbor-group RR-services-group

vrf Test rd auto address-family ipv4 unicast redistribute connected

segment-routing traffic-eng logging policy status

segment-list sl-cxr1 index 10 mpls label 16294

policy pol-foo color 129 end-point ipv4 4.4.4.4

candidate-paths preference 100

explicit segment-list sl-cxr1

Configuration on router R2: vrf Test address-family ipv4 unicast import route-target

1:150

export route-policy SET_COLOR_RED_HI_BW export route-target

1:150

interface TenGigE0/1/0/1 description cxr1 to exr1 ipv4 address 10.0.20.1 255.255.255.0

extcommunity-set opaque color129-red-igp

129 end-set

route-policy PASS pass end-policy

route-policy SET_COLOR_RED_HI_BW set extcommunity color color129-red-igp pass end-policy

router isis 1 is-type level-2-only net 49.0001.0000.0000.0004.00

log adjacency changes

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BGP Routes on PE – Color Based Steering affinity-map RED bit-position 28 affinity-map BLUE bit-position 29 affinity-map GREEN bit-position 30 flex-algo 128 priority 228

flex-algo 129 priority 229

flex-algo 130 priority 230

address-family ipv4 unicast metric-style wide advertise link attributes router-id 4.4.4.4

segment-routing mpls

interface Loopback0 address-family ipv4 unicast prefix-sid index 4 prefix-sid algorithm 128 index 284 prefix-sid algorithm 129 index 294 prefix-sid algorithm 130 index 304

interface GigabitEthernet0/0/0/0 point-to-point address-family ipv4 unicast

interface TenGigE0/1/0/1 point-to-point address-family ipv4 unicast

router bgp 65000 bgp router-id 4.4.4.4

address-family ipv4 unicast

address-family vpnv4 unicast

neighbor-group RR-services-group remote-as 65000 update-source Loopback0 address-family ipv4 unicast

address-family vpnv4 unicast

neighbor 1.1.1.1

use neighbor-group RR-services-group

neighbor 2.2.2.2

use neighbor-group RR-services-group

vrf Test rd auto address-family ipv4 unicast

redistribute connected neighbor 25.1.1.2

remote-as 4 address-family ipv4 unicast

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route-policy PASS in route-policy PASS out

segment-routing

end

BGP Routes on PE – Color Based Steering

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Configure Segment Routing Path Computation

Element

The Segment Routing Path Computation Element (SR-PCE) provides stateful PCE functionality by extending the existing IOS-XR PCEP functionality with additional capabilities. SR-PCE is supported on the MPLS data plane and IPv4 control plane.

Note The Cisco IOS XRv 9000 is the recommended platform to act as the SR-PCE. Refer to the Cisco IOS XRv

9000 Router Installation and Configuration Guide for more information.

•

About SR-PCE, on page 119

•

Configure SR-PCE, on page 120

•

PCE-Initiated SR Policies, on page 123

About SR-PCE

Note For more information on PCE, PCC, and PCEP, refer to the Path Computation Element section in the MPLS

Configuration Guide for Cisco NCS 6000 Series Routers .

SR-PCE learns topology information by way of IGP (OSPF or IS-IS) or through BGP Link-State (BGP-LS).

SR-PCE is capable of computing paths using the following methods:

• TE metric—SR-PCE uses the TE metric in its path calculations to optimize cumulative TE metric.

• IGP metric—SR-PCE uses the IGP metric in its path calculations to optimize reachability.

• LSP Disjointness—SR-PCE uses the path computation algorithms to compute a pair of disjoint LSPs.

The disjoint paths can originate from the same head-end or different head-ends. Disjoint level refers to

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Configure SR-PCE the type of resources that should not be shared by the two computed paths. SR-PCE supports the following disjoint path computations:

• Link – Specifies that links are not shared on the computed paths.

• Node – Specifies that nodes are not shared on the computed paths.

• SRLG – Specifies that links with the same SRLG value are not shared on the computed paths.

• SRLG-node – Specifies that SRLG and nodes are not shared on the computed paths.

When the first request is received with a given disjoint-group ID, the first LSP is computed, encoding the shortest path from the first source to the first destination. When the second LSP request is received with the same disjoint-group ID, information received in both requests is used to compute two disjoint paths: one path from the first source to the first destination, and another path from the second source to the second destination. Both paths are computed at the same time.

Configure SR-PCE

This task explains how to configure SR-PCE.

Before you begin

The Cisco IOS XRv 9000 is the recommended platform to act as the SR-PCE.

SUMMARY STEPS

configure

pce

address ipv4 address

state-sync ipv4 address

tcp-buffer size size

password { clear | encrypted } password

segment-routing { strict-sid-only | te-latency }

timers

keepalive time

10.

minimum-peer-keepalive time

11.

reoptimization time

12.

exit

DETAILED STEPS

Step 1

Command or Action configure

Example:

RP/0/RP0/CPU0:router# configure

Purpose

Enters XR Config mode.

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Configure SR-PCE

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Step 8

Step 9

Command or Action pce

Example:

RP/0/RP0/CPU0:router(config)# pce

Purpose

Enables PCE and enters PCE configuration mode.

address ipv4 address

Example:

RP/0/RP0/CPU0:router(config-pce)# address ipv4

192.168.0.1

Configures a PCE IPv4 address.

state-sync ipv4 address

Example:

RP/0/RP0/CPU0:router(config-pce)# state-sync ipv4

192.168.0.3

Configures the remote peer for state synchronization.

tcp-buffer size size

Example:

RP/0/RP0/CPU0:router(config-pce)# tcp-buffer size

1024000

Configures the transmit and receive TCP buffer size for each PCEP session, in bytes. The default buffer size is

256000. The valid range is from 204800 to 1024000.

password

Example:

{ clear | encrypted } password

RP/0/RP0/CPU0:router(config-pce)# password encrypted pwd1

Enables TCP MD5 authentication for all PCEP peers. Any

TCP segment coming from the PCC that does not contain a MAC matching the configured password will be rejected.

Specify if the password is encrypted or clear text.

segment-routing { strict-sid-only | te-latency } Configures the segment routing algorithm to use strict SID or TE latency.

Example:

RP/0/RP0/CPU0:router(config-pce)# segment-routing strict-sid-only

Note This setting is global and applies to all LSPs that request a path from this controller.

timers

Example:

RP/0/RP0/CPU0:router(config-pce)# timers

keepalive time

Example:

Enters timer configuration mode.

Configures the timer value for locally generated keep-alive messages. The default time is 30 seconds.

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Configure the Disjoint Policy (Optional)

Step 10

Step 11

Step 12

Command or Action

RP/0/RP0/CPU0:router(config-pce-timers)# keepalive

Purpose

minimum-peer-keepalive time

Example:

RP/0/RP0/CPU0:router(config-pce-timers)# minimum-peer-keepalive 30

Configures the minimum acceptable keep-alive timer that the remote peer may propose in the PCEP OPEN message during session establishment. The default time is 20 seconds.

reoptimization time

Example:

RP/0/RP0/CPU0:router(config-pce-timers)# reoptimization 600

Configures the re-optimization timer. The default timer is

1800 seconds.

exit

Example:

RP/0/RP0/CPU0:router(config-pce-timers)# exit

Exits timer configuration mode and returns to PCE configuration mode.

Configure the Disjoint Policy (Optional)

This task explains how to configure the SR-PCE to compute disjointness for a pair of LSPs signaled by PCCs that do not include the PCEP association group-ID object in their PCEP request. This can be beneficial for deployments where PCCs do not support this PCEP object or when the network operator prefers to manage the LSP disjoint configuration centrally.

SUMMARY STEPS

disjoint-path

group-id value type { link | node | srlg | srlg-node } [ sub-id value ]

strict

lsp { 1 | 2 } pcc ipv4 address lsp-name lsp_name [ shortest-path ]

DETAILED STEPS

Step 1

Command or Action disjoint-path

Example:

RP/0/RP0/CPU0:router(config-pce)# disjoint-path

Purpose

Enters disjoint configuration mode.

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PCE-Initiated SR Policies

Step 2

Step 3

Step 4

Command or Action Purpose

group-id value type srlg-node

Example:

} [

{ link

sub-id value ]

| node | srlg |

RP/0/RP0/CPU0:router(config-pce-disjoint)# group-id

1 type node sub-id 1

Configures the disjoint group ID and defines the preferred level of disjointness (the type of resources that should not be shared by the two paths):

• link —Specifies that links are not shared on the computed paths.

• node —Specifies that nodes are not shared on the computed paths.

• srlg —Specifies that links with the same SRLG value are not shared on the computed paths.

• srlg-node —Specifies that SRLG and nodes are not shared on the computed paths.

If a pair of paths that meet the requested disjointness level cannot be found, then the paths will automatically fallback to a lower level:

• If the requested disjointness level is SRLG or node, then link-disjoint paths will be computed.

• If the requested disjointness level was link, or if the first fallback from SRLG or node disjointness failed, then the lists of segments encoding two shortest paths, without any disjointness constraint, will be computed.

strict

Example:

RP/0/RP0/CPU0:router(config-pce-disjoint)# strict

(Optional) Prevents the automatic fallback behavior of the preferred level of disjointness. If a pair of paths that meet the requested disjointness level cannot be found, the disjoint calculation terminates and no new path is provided. The existing path is not modified.

lsp { 1 | 2 } pcc ipv4 address lsp-name lsp_name

[ shortest-path ]

Adds LSPs to the disjoint group.

Example:

RP/0/RP0/CPU0:router(config-pce-disjoint)# lsp 1 pcc ipv4 192.168.0.1 lsp-name rtrA_t1 shortest-path

RP/0/RP0/CPU0:router(config-pce-disjoint)# lsp 2 pcc ipv4 192.168.0.5 lsp-name rtrE_t2

The shortest-path keyword forces one of the disjoint paths to follow the shortest path from the source to the destination.

This option can only be applied to the the first LSP specified.

PCE-Initiated SR Policies

An SR-TE policy can be configured on the path computation element (PCE) to reduce link congestion or to minimize the number of network touch points.

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PCE-Initiated SR Policies

Note The PCE-initiated SR-TE policies are entered in PCE configuration mode. For more information on configuring

SR-TE policies, see the

SR-TE Policy Overview, on page 37 .

To minimize the number of network touch points, an application, such as a Network Services Orchestrator

(NSO), can request the PCE to create an SR-TE policy. PCE deploys the SR-TE policy using PCC-PCE communication protocol (PCEP).

PCE sends a PCInitiate message to the PCC.

If the PCInitiate message is valid, the PCC sends a PCRpt message; otherwise, it sends PCErr message.

If the PCInitiate message is accepted, the PCE updates the SR-TE policy by sending PCUpd message.

You can achieve high-availability by configuring multiple PCEs with SR-TE policies. If the head-end (PCC) loses connectivity with one PCE, another PCE can assume control of the SR-TE policy.

Configuration Example: PCE-Initiated SR Policy with Explicit SID List

To configure a PCE-initiated SR-TE policy, you must complete the following configurations:

Enter PCE configuration mode.

Create the segment list.

Note When configuring an explicit path using IP addresses of intermediate links, the SR-TE process selects either the protected or the unprotected Adj-SID of the link, depending on the order in which the Adj-SIDs were received.

Create the policy.

/* Enter PCE configuration mode and create the SR-TE segment lists */

Router# configure

Router(config)# pce

/* Create the SR-TE segment lists */

Router(config-pce)# segment-routing

Router(config-pce-sr)# traffic-eng

Router(config-pce-sr-te)# segment-list name addr2a

Router(config-pce-sr-te-sl)# index 10 address ipv4 1.1.1.2

Router(config-pce-sr-te-sl)# index 20 address ipv4 10.2.3.2

Router(config-pce-sr-te-sl)# index 30 address ipv4 1.1.1.4

Router(config-pce-sr-te-sl)# exit

/* Create the SR-TE policy */

Router(config-pce-sr-te)# peer ipv4 1.1.1.1

Router(config-pce-sr-te)# policy P1

Router(config-pce-sr-te-policy)# color 2 end-point ipv4 2.2.2.2

Router(config-pce-sr-te-policy)# candidate-paths

Router(config-pce-sr-te-policy-path)# preference 50

Router(config-pce-sr-te-policy-path-preference)# explicit segment-list addr2a

Router(config-pce-sr-te-pp-info)# commit

Router(config-pce-sr-te-pp-info)# end

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Router(config)#

Running Config pce segment-routing traffic-eng segment-list name addr2a index 1 address ipv4 14.14.14.4

peer ipv4 1.1.1.1

policy P1 color 2 end-point ipv4 2.2.2.2

candidate-paths

preference 50 explicit segment-list addr2a

PCE-Initiated SR Policies

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C H A P T E R

Configure Performance Measurement

Network performance metrics is a critical measure for traffic engineering (TE) in service provider networks.

Network performance metrics include the following:

• Packet loss

• Delay

• Delay variation

• Bandwidth utilization

These network performance metrics provide network operators information about the performance characteristics of their networks for performance evaluation and help to ensure compliance with service level agreements.

The service-level agreements (SLAs) of service providers depend on the ability to measure and monitor these network performance metrics. Network operators can use performance measurement (PM) feature to monitor the network metrics for links and end-to-end TE label switched paths (LSPs).

The following table explains the functionalities supported by performance measurement feature for measuring delay for links.

Table 3: Performance Measurement Functionalities

Functionality Details

Profiles You can configure different profiles for different types of delay measurements.

Use the "interfaces" delay profile type for link-delay measurement. Delay profile allows you to schedule probe and configure metric advertisement parameters for delay measurement.

Protocols

Probe and burst scheduling

Two-Way Active Measurement Protocol (TWAMP) Light (using RFC 5357 with

IP/UDP encap).

Schedule probes and configure metric advertisement parameters for delay measurement.

Metric advertisements Advertise measured metrics periodically using configured thresholds. Also supports accelerated advertisements using configured thresholds.

Measurement history and counters

Maintain packet delay and loss measurement history, session counters, and packet advertisement counters.

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Measurement Modes

•

Measurement Modes, on page 128

•

Link Delay Measurement, on page 130

Measurement Modes

The following table compares the different hardware and timing requirements for the measurement modes supported in SR PM.

Table 4: Measurement Mode Requirements

Measurement Mode PTP Clock Synchronization between Sender and Reflector

One-way

Two-way

Sender:

PTP-Capable HW and HW

Timestamping

Required

Reflector:

PTP-Capable HW and HW

Timestamping

Required

Not Required

One-Way

One-way measurement mode provides the most precise form of one-way delay measurement. PTP-capable hardware and hardware timestamping are required on both Sender and Reflector, with PTP Clock

Synchronization between Sender and Reflector.

Delay measurement in one-way mode is calculated as (T2 – T1).

Figure 8: One-Way

The PM query and response for one-way delay measurement can be described in the following steps:

The local-end router sends PM query packets periodically to the remote side once the egress line card on the router applies timestamps on packets.

The ingress line card on the remote-end router applies time-stamps on packets as soon as they are received.

The remote-end router sends the PM packets containing time-stamps back to the local-end router.

One-way delay is measured using the time-stamp values in the PM packet.

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Measurement Modes

Two-Way

Two-way meaurement mode provides two-way measurements. PTP-capable hardware and hardware timestamping are required on both Sender and Reflector, but PTP clock synchronization between Sender and

Reflector is not required.

Delay measurements in two-way mode are calculated as follows:

• Two-Way Delay = (T4 – T1) – (T3 – T2)

• One-Way Delay = Two-Way Delay/2

Figure 9: Two-Way

The PM query and response for two-way delay measurement can be described in the following steps:

The local-end router sends PM query packets periodically to the remote side once the egress line card on the router applies timestamps on packets.

Ingress line card on the remote-end router applies time-stamps on packets as soon as they are received.

The remote-end router sends the PM packets containing time-stamps back to the local-end router. The remote-end router time-stamps the packet just before sending it for two-way measurement.

The local-end router time-stamps the packet as soon as the packet is received for two-way measurement.

One-way delay and optionally two-way delay is measured using the time-stamp values in the PM packet.

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Link Delay Measurement

Table 5: Feature History Table

Feature Name

Segment Routing Performance

Measurement for Link Delay

Measurement on Link Bundles

Release Information

Release 7.2.2

Feature Description

This enhancement introduces support for using link bundles with

Segment Routing Performance

Measurement link delay measurement

A link bundle is a group of one or more ports that are aggregated together and treated as a single link.

Link bundles allow you to group multiple point-to-point links together into one logical link and provide higher bidirectional bandwidth, redundancy, and load balancing between two routers.

The PM for link delay uses the IP/UDP packet format defined in RFC 5357 (TWAMP-Light) for probes.

Two-Way Active Measurement Protocol (TWAMP) adds two-way or round-trip measurement capabilities.

TWAMP employs time stamps applied at the echo destination (reflector) to enable greater accuracy. In the case of TWAMP Light, the Session-Reflector doesn’t necessarily know about the session state. The

Session-Reflector simply copies the Sequence Number of the received packet to the Sequence Number field of the reflected packet. The controller receives the reflected test packets and collects two-way metrics. This architecture allows for collection of two-way metrics.

Usage Guidelines and Restrictions for PM for Link Delay

The following restrictions and guidelines apply for the PM for link delay feature for different links.

• For broadcast links, only point-to-point (P2P) links are supported. P2P configuration on IGP is required for flooding the value.

• For link bundles, the hashing function may select a member link for forwarding but the reply may come from the remote line card on a different member link of the bundle.

• For one-way delay measurement, clocks should be synchronized on two end-point nodes of the link using

PTP.

Configuration Example: PM for Link Delay

This example shows how to configure performance-measurement functionalities for link delay as a global default profile. The default values for the different parameters in the PM for link delay is given as follows:

• probe measurement mode : The default measurement mode for probe is two-way delay measurement.

If you are configuring one-way delay measurement, hardware clocks must be synchronized between the local-end and remote-end routers using precision time protocol (PTP). See

Measurement Modes, on page

128

for more information.

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• protocol : Interface delay measurement using RFC 5357 with IP/UDP encap (TWAMP-Light).

• burst interval : Interval for sending probe packet. The default value is 3000 milliseconds and the range is from 30 to 15000 milliseconds.

• computation interval : Interval for metric computation. Default is 30 seconds; range is 1 to 3600 seconds.

• periodic advertisement : Periodic advertisement is enabled by default.

• periodic-advertisement interval : The default value is 120 seconds and the interval range is from 30 to

3600 seconds.

• periodic-advertisement threshold : Checks the minimum-delay metric change for threshold crossing for periodic advertisement. The default value is 10 percent and the range is from 0 to 100 percent.

• periodic-advertisement minimum change : The default value is 1000 microseconds (usec) and the range is from 0 to 100000 microseconds.

• accelerated advertisement : Accelerated advertisement is disabled by default.

• accelerated-advertisement threshold : Checks the minimum-delay metric change for threshold crossing for accelerated advertisement. The default value is 20 percent and the range is from 0 to 100 percent.

• accelerated-advertisement minimum change : The default value is 500 microseconds and the range is from 0 to 100000 microseconds.

RP/0/0/CPU0:router(config)# performance-measurement delay-profile interfaces

RP/0/0/CPU0:router(config-pm-dm-intf)# probe

RP/0/0/CPU0:router(config-pm-dm-intf-probe)# measurement-mode one-way

RP/0/0/CPU0:router(config-pm-dm-intf-probe)# burst-interval 60

RP/0/0/CPU0:router(config-pm-dm-intf-probe)# computation-interval 60

RP/0/0/CPU0:router(config-pm-dm-intf-probe)# exit

RP/0/0/CPU0:router(config-pm-dm-intf)# advertisement periodic

RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# interval 120

RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# threshold 20

RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# minimum-change 1000

RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# exit

RP/0/0/CPU0:router(config-pm-dm-intf)# advertisement accelerated

RP/0/0/CPU0:router(config-pm-dm-intf-adv-acc)# threshold 30

RP/0/0/CPU0:router(config-pm-dm-intf-adv-acc)# minimum-change 1000

RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# exit

Configure the UDP Destination Port

Configuring the UDP port for TWAMP-Light protocol is optional. By default, PM uses port 862 as the

TWAMP-reserved UDP destination port for delay.

The UDP port is configured for each PM measurement probe type (delay, loss, protocol, authentication mode, etc.) on querier and responder nodes. If you configure a different UDP port, the UDP port for each PM measurement probe type must match on the querier and the responder nodes.

Note The same UDP destination port is used for delay measurement for links and SR Policy.

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Link Delay Measurement

This example shows how to configure the UDP destination port for delay.

Router(config)# performance-measurement

Router(config-perf-meas)# protocol twamp-light

Router(config-pm-protocol)# measurement delay unauthenticated

Router(config-pm-proto-mode)# querier-dst-port 12000

Enable PM for Link Delay Over an Interface

This example shows how to enable PM for link delay over an interface.

RP/0/0/CPU0:router(config)# performance-measurement

RP/0/0/CPU0:router(config-perf-meas)# interface TenGigE0/0/0/0

RP/0/0/CPU0:router(config-pm-intf)# delay-measurement

RP/0/0/CPU0:router(config-pm-dm-intf)# exit

The source and destination IP addresses used in the OAM packet are determined by the IP address present on the interface where the delay-measurement operation is enabled.

the following rules apply to determine the source and destination IP addresses used in the OAM packet:

• If an IPv4 address is configured under the interface, then:

• OAM packet source IP address = Interface's IPv4 address

• OAM packet destination IP address = 127.0.0.0

• Else, if an IPv6 global address is configured under the interface, then:

• OAM packet source IP address = Interface's IPv6 global address

• OAM packet destination IP address = 0::ff:127.0.0.0

This example shows how to enable PM for link delay over an interface with IPv4 address configured: interface TenGigE0/0/0/0 ipv4 address 10.10.10.1 255.255.255.0

performance-measurement interface TenGigE0/0/0/0 delay-measurement

This example shows how to enable PM for link delay over an interface IPv6 address configured: interface TenGigE0/0/0/0 ipv6 address 10:10:10::1/64 performance-measurement interface TenGigE0/0/0/0 delay-measurement

Verification

RP/0/0/CPU0:router# show performance-measurement profile interface

Thu Dec 12 14:13:16.029 PST

-------------------------------------------------------------------------------

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0/0/CPU0

-------------------------------------------------------------------------------

Interface Delay-Measurement:

Profile configuration:

Measurement Type

Probe computation interval

Type of services

Burst interval

Burst count

: Two-Way

: 30 (effective: 30) seconds

: Traffic Class: 6, DSCP: 48

: 3000 (effective: 3000) mSec

: 10 packets

Encap mode

Payload Type

Destination sweeping mode

Periodic advertisement

Interval

Threshold

Minimum-Change

Advertisement accelerated

Threshold crossing check

: UDP

: TWAMP-light

: Disabled

: Enabled

: 120 (effective: 120) sec

: 10%

: 500 uSec

: Disabled

: Minimum-delay

RP/0/0/CPU0:router# show performance-measurement summary detail location 0/2/CPU0

Thu Dec 12 14:09:59.162 PST

-------------------------------------------------------------------------------

0/2/CPU0

-------------------------------------------------------------------------------

Total interfaces

Total SR Policies

: 1

: 0

Total RSVP-TE tunnels

Total Maximum PPS

Total Interfaces PPS

Maximum Allowed Multi-hop PPS

Multi Hop Requested PPS

Dampened Multi Hop Requested PPS

Inuse Burst Interval Adjustment Factor

: 0

: 2000 pkts/sec

: 0 pkts/sec

: 2000 pkts/sec

: 0 pkts/sec (0% of max allowed)

: 0% of max allowed

: 100% of configuration

Interface Delay-Measurement:

Total active sessions

Counters:

Packets:

Total sent

Total received

Errors:

TX:

Reason interface down

Reason no MPLS caps

Reason no IP address

Reason other

RX:

Reason negative delay

Reason delay threshold exceeded

Reason missing TX timestamp

Reason missing RX timestamp

Reason probe full

Reason probe not started

Reason control code error

Reason control code notif

Probes:

Total started

Total completed

Total incomplete

Total advertisements

: 1

: 26

: 0

: 3

: 2

: 0

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SR Policy Delay-Measurement:

Total active sessions

Counters:

Packets:

Total sent

Total received

Errors:

TX:

Reason interface down

Reason no MPLS caps

Reason no IP address

Reason other

RX:

Reason negative delay

Reason delay threshold exceeded

Reason missing TX timestamp

Reason missing RX timestamp

Reason probe full

Reason probe not started

Reason control code error

Reason control code notif

Probes:

Total started

Total completed

Total incomplete

Total advertisements

RSVP-TE Delay-Measurement:

Total active sessions

Counters:

Packets:

Total sent

Total received

Errors:

TX:

Reason interface down

Reason no MPLS caps

Reason no IP address

Reason other

RX:

Reason negative delay

Reason delay threshold exceeded

Reason missing TX timestamp

Reason missing RX timestamp

Reason probe full

Reason probe not started

Reason control code error

Reason control code notif

Probes:

Total started

Total completed

Total incomplete

Total advertisements

: 0

Global Delay Counters:

Total packets sent

Total query packets received

Total invalid session id

Total missing session

: 26

: 0

RP/0/0/CPU0:router# show performance-measurement interfaces detail

Thu Dec 12 14:16:09.692 PST

-------------------------------------------------------------------------------

0/0/CPU0

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-------------------------------------------------------------------------------

0/2/CPU0

-------------------------------------------------------------------------------

Interface Name: GigabitEthernet0/2/0/0 (ifh: 0x1004060)

Delay-Measurement

Loss-Measurement

: Enabled

: Disabled

Configured IPv4 Address

Configured IPv6 Address

Link Local IPv6 Address

Configured Next-hop Address

Local MAC Address

: 10.10.10.2

: 10:10:10::2

: fe80::3a:6fff:fec9:cd6b

: Unknown

: 023a.6fc9.cd6b

Next-hop MAC Address

Primary VLAN Tag

Secondary VLAN Tag

State

: 0291.e460.6707

: None

: Up

Delay Measurement session:

Session ID : 1

Last advertisement:

Advertised at: Dec 12 2019 14:10:43.138 (326.782 seconds ago)

Advertised reason: First advertisement

Advertised delays (uSec): avg: 839, min: 587, max: 8209, variance: 297

Next advertisement:

Threshold check scheduled in 1 more probe (roughly every 120 seconds)

Aggregated delays (uSec): avg: 751, min: 589, max: 905, variance: 112

Rolling average (uSec): 756

Current Probe:

Started at Dec 12 2019 14:15:43.154 (26.766 seconds ago)

Packets Sent: 9, received: 9

Measured delays (uSec): avg: 795, min: 631, max: 1199, variance: 164

Next probe scheduled at Dec 12 2019 14:16:13.132 (in 3.212 seconds)

Next burst packet will be sent in 0.212 seconds

Burst packet sent every 3.0 seconds

Probe samples:

Packet Rx Timestamp

Dec 12 2019 14:15:43.156

Dec 12 2019 14:15:46.156

Dec 12 2019 14:15:49.156

Dec 12 2019 14:15:52.157

Dec 12 2019 14:15:55.156

Dec 12 2019 14:15:58.156

Dec 12 2019 14:16:01.157

Dec 12 2019 14:16:04.157

Dec 12 2019 14:16:07.157

Measured Delay (nsec)

689223

876561

913548

1199620

794008

631437

656440

658267

736880

You can also use the following commands for verifying the PM for link delay on the local-end router.

Command show performance-measurement history probe interfaces [ interface ]

Description

Displays the PM link-delay probe history for interfaces.

show performance-measurement history aggregated interfaces [ interface ] show performance-measurement history advertisement interfaces [ interface ]

Displays the PM link-delay aggregated history for interfaces.

Displays the PM link-delay advertisement history for interfaces.

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Command Description show performance-measurement counters [interface interface ] [location location-name ]

Displays the PM link-delay session counters.

You can also use the following commands for verifying the PM for link-delay configuration on the remote-end router.

Command Description show performance-measurement responder summary [ location location-name ] show performance-measurement responder interfaces [ interface ] show performance-measurement responder counters [ interface interface location-name ]

] [ location

Displays the PM for link-delay summary on the remote-end router (responder).

Displays PM for link-delay for interfaces on the remote-end router.

Displays the PM link-delay session counters on the remote-end router.

SR Performance Measurement Named Profiles

You can create a named performance measurement profile for delay or liveness. Details:

Delay Profile

This example shows how to create a named SR performance measurement delay profile.

Router(config)# performance-measurement delay-profile sr-policy name profile2

Router(config-pm-dm-srpolicy)# probe

Router(config-pm-dm-srpolicy-probe)# burst-interval 60

Router(config-pm-dm-srpolicy-probe)# computation-interval 60

Router(config-pm-dm-srpolicy-probe)# protocol twamp-light

Router(config-pm-dm-srpolicy-probe)# tos dscp 63

Router(config-pm-dm-srpolicy)# advertisement

Router(config-pm-dm-srpolicy-adv)# periodic

Router(config-pm-dm-srpolicy-adv-per)# interval 60

Router(config-pm-dm-srpolicy-adv-per)# minimum-change 1000

Router(config-pm-dm-srpolicy-adv-per)# threshold 20

Router(config-pm-dm-srpolicy-adv-per)# commit

Apply the delay profile for an SR Policy.

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# policy TEST

Router(config-sr-te-policy)# color 4 end-point ipv4 10.10.10.10

Router(config-sr-te-policy)# performance-measurement

Router(config-sr-te-policy-perf-meas)# delay-measurement delay-profile name profile2

Router(config-sr-te-policy)#candidate-paths

Router(config-sr-te-policy-path)#preference 100

Router(config-sr-te-policy-path-pref)#explicit segment-list LIST1

Router(config-sr-te-pp-info)#weight 2

Router(config-sr-te-policy-path-pref)#explicit segment-list LIST2

Router(config-sr-te-pp-info)#weight 3

Running Configuration

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Router# show run segment-routing traffic-eng policy TEST segment-routing traffic-eng policy TEST color 4 end-point ipv4 10.10.10.10

candidate-paths preference 100 explicit segment-list LIST1 weight 2

explicit segment-list LIST2 weight 3

performance-measurement delay-measurement delay-profile name profile2

Verification

Router# show performance-measurement profile named-profile delay sr-policy name profile2

----------------------------

0/RSP0/CPU0

----------------------------

SR Policy Delay Measurement Profile Name: profile2

Profile configuration:

Measurement mode : One-way

Protocol type

Encap mode

: TWAMP-light

: UDP

Type of service:

PM-MPLS traffic class

TWAMP-light DSCP

Probe computation interval

Burst interval

Packets per computation interval

Periodic advertisement

Interval

Threshold

Minimum-change

: 6

: 63

: 60 (effective: 60) seconds

: 60 (effective: 60) mSec

: 1000

: Enabled

: 60 (effective: 60) sec

: 20%

: 1000 uSec

: Disabled Advertisement accelerated

Advertisement logging:

Delay exceeded

Threshold crossing check

Router alert

Destination sweeping mode

Liveness detection parameters:

Multiplier

Logging state change

: Disabled (default)

: Maximum-delay

: Disabled (default)

: Disabled

: 3

: Disabled

On-Demand SR Policy

Router(config-sr-te)# on-demand color 20

Router(config-sr-te-color)# performance-measurement delay-measurement

Router(config-sr-te-color-delay-meas)# delay-profile name profile2

Router(config-sr-te-color-delay-meas)# commit

Running Configuration

Router# show run segment-routing traffic-eng on-demand color 20 segment-routing traffic-eng on-demand color 20

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Link Delay Measurement performance-measurement delay-measurement delay-profile name profile2

Liveness Profile

This example shows how to create a named SR performance measurement liveness profile.

Router(config)# performance-measurement liveness-profile sr-policy name profile3

Router(config-pm-ld-srpolicy)# probe

Router(config-pm-ld-srpolicy-probe)# burst-interval 60

Router(config-pm-ld-srpolicy-probe)# measurement-mode loopback

Router(config-pm-ld-srpolicy-probe)# tos dscp 10

Router(config-pm-ld-srpolicy-probe)# liveness-detection

Router(config-pm-ld-srpolicy-probe)# multiplier 5

Router(config-pm-ld-srpolicy-probe)# commit

Apply the liveness profile for the SR policy

This example shows how to enable PM for SR policy liveness for a specific policy.

For the same policy, you cannot enable delay-measurement (delay-profile) and liveness-detection

(liveness-profile) at the same time. For example, if delay measurement is enabled, use the no delay-measurement command to disable it, and then enable the following command for enabling liveness detection.

Router(config)# segment-routing traffic-eng

Router(config-sr-te)# policy TRST2

Router(config-sr-te-policy)# color 40 end-point ipv4 20.20.20.20

Router(config-sr-te-policy)#candidate-paths

Router(config-sr-te-policy-path)#preference 50

Router(config-sr-te-policy-path-pref)#explicit segment-list LIST3

Router(config-sr-te-pp-info)#weight 2

Router(config-sr-te-policy-path-pref)#explicit segment-list LIST4

Router(config-sr-te-pp-info)#weight 3

Router(config-sr-te-policy)# performance-measurement

Router(config-sr-te-policy-perf-meas)# liveness-detection liveness-profile name profile3

Running Configuration

Router# show run segment-routing traffic-eng policy TRST2 segment-routing traffic-eng policy TRST2 color 40 end-point ipv4 20.20.20.20

candidate-paths preference 50 explicit segment-list LIST3 weight 2

explicit segment-list LIST4

weight 3

performance-measurement liveness-detection liveness-profile name profile3

Verification

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Link Delay Measurement

Router# show performance-measurement profile named-profile delay sr-policy name profile3

-----------

0/RSP0/CPU0

-----------

SR Policy Liveness Detection Profile Name: profile1

Profile configuration:

Measurement mode

Protocol type

Type of service:

: Loopback

: TWAMP-light

TWAMP-light DSCP

Burst interval

Destination sweeping mode

Liveness detection parameters:

Multiplier

Logging state change

: 10

: 60 (effective: 60) mSec

: Disabled

: 3

: Disabled

SR Policy Liveness Detection Profile Name: profile3

Profile configuration:

Measurement mode : Loopback

Protocol type

Type of service:

: TWAMP-light

TWAMP-light DSCP

Burst interval

Destination sweeping mode

Liveness detection parameters:

Multiplier

Logging state change

: 10

: 60 (effective: 60) mSec

: Disabled

: 3

: Disabled

On-Demand SR Policy

For the same policy, you cannot enable delay-measurement (delay-profile) and liveness-detection

(liveness-profile) at the same time. For example, to disable delay measurement, use the no delay-measurement command, and then enable the following command for enabling liveness detection.

Router(config-sr-te)#on-demand color 30

Router(config-sr-te-color)#performance-measurement

Router(config-sr-te-color-pm)# liveness-detection liveness-profile name profile1

Router(config-sr-te-color-delay-meas)# commit

Running Configuration

Router# show run segment-routing traffic-eng on-demand color 30 segment-routing traffic-eng on-demand color 30 performance-measurement liveness-detection liveness-profile name profile3

Verification

Router# show performance-measurement profile named-profile liveness sr-policy name profile3

--------------------

0/RSP0/CPU0

--------------------

SR Policy Liveness Detection Profile Name: profile3

Profile configuration:

Measurement mode : Loopback

Protocol type

Type of service:

: TWAMP-light

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Link Delay Measurement

TWAMP-light DSCP

Burst interval

Destination sweeping mode

Liveness detection parameters:

Multiplier

Logging state change

Configure Performance Measurement

: 10

: 60 (effective: 60) mSec

: Disabled

: 3

: Disabled

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C H A P T E R

Configure Topology-Independent Loop-Free

Alternate (TI-LFA)

Topology-Independent Loop-Free Alternate (TI-LFA) uses segment routing to provide link protection in topologies where other fast reroute techniques cannot provide protection.

• Classic Loop-Free Alternate (LFA) is topology dependent, and therefore cannot protect all destinations in all networks. A limitation of LFA is that, even if one or more LFAs exist, the optimal LFA may not always be provided.

• Remote LFA (RLFA) extends the coverage to 90-95% of the destinations, but it also does not always provide the most desired repair path. RLFA also adds more operational complexity by requiring a targeted

LDP session to the RLFAs to protect LDP traffic.

TI-LFA provides a solution to these limitations while maintaining the simplicity of the IPFRR solution.

The goal of TI-LFA is to reduce the packet loss that results while routers converge after a topology change due to a link failure. Rapid failure repair (< 50 msec) is achieved through the use of pre-calculated backup paths that are loop-free and safe to use until the distributed network convergence process is completed.

The optimal repair path is the path that the traffic will eventually follow after the IGP has converged. This is called the post-convergence path. This path is preferred for the following reasons:

• Optimal for capacity planning — During the capacity-planning phase of the network, the capacity of a link is provisioned while taking into consideration that such link with be used when other links fail.

• Simple to operate — There is no need to perform a case-by-case adjustments to select the best LFA among multiple candidate LFAs.

• Fewer traffic transitions — Since the repair path is equal to the post-convergence path, the traffic switches paths only once.

The following topology illustrates the optimal and automatic selection of the TI-LFA repair path.

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Usage Guidelines and Limitations

Figure 10: TI-LFA Repair Path

Configure Topology-Independent Loop-Free Alternate (TI-LFA)

Node 2 protects traffic to destination Node 5.

With classic LFA, traffic would be steered to Node 4 after a failure of the protected link. This path is not optimal, since traffic is routed over edge node Node 4 that is connected to lower capacity links.

TI-LFA calculates a post-convergence path and derives the segment list required to steer packets along the post-convergence path without looping back.

In this example, if the protected link fails, the shortest path from Node2 to Node5 would be:

Node2

→

Node6

→

Node7

→

Node3

→

Node5

Node7 is the PQ-node for destination Node5. TI-LFA encodes a single segment (prefix SID of Node7) in the header of the packets on the repair path.

•

Usage Guidelines and Limitations, on page 142

•

Configuring TI-LFA for IS-IS, on page 143

•

Configuring TI-LFA for OSPF, on page 145

Usage Guidelines and Limitations

The TI-LFA guidelines and limitations are listed below:

TI-LFA Functionality IS-IS

Protected Traffic Types

OSPFv2

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TI-LFA Functionality

Protection for SR labeled traffic

Protection of IPv4 unlabeled traffic

Protection of IPv6 unlabeled traffic

Protection Types

Link Protection

Node Protection

Local SRLG Protection

Weighted Remote SRLG Protection

Line Card Disjoint Protection

IS-IS

Supported

(IS-ISv4)

Unsupported

Supported

Interface Types

Ethernet Interfaces

Ethernet Bundle Interfaces

Supported

TI-LFA over GRE Tunnel as Protecting Interface

Additional Functionality

BFD-triggered

BFDv6-triggered

Supported

Prefer backup path with lowest total metric Supported

Prefer backup path from ECMP set Supported

Prefer backup path from non-ECMP set Supported

Load share prefixes across multiple backups paths Supported

Limit backup computation up to the prefix priority Supported

Unless specified, IS-IS support is IS-ISv4 and IS-ISv6

OSPFv2

Supported

N/A

Supported

Unsupported

Supported

N/A

Supported

Configuring TI-LFA for IS-IS

This task describes how to enable per-prefix Topology Independent Loop-Free Alternate (TI-LFA) computation to converge traffic flows around link failures.

Before you begin

Ensure that the following topology requirements are met:

• Router interfaces are configured as per the topology.

• Routers are configured with IS-IS.

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Configuring TI-LFA for IS-IS

• Segment routing for IS-IS is configured. See

Enabling Segment Routing for IS-IS Protocol, on page 11 .

SUMMARY STEPS

configure

router isis instance-id

interface type interface-path-id

address-family ipv4 [ unicast ]

fast-reroute per-prefix

fast-reroute per-prefix ti-lfa

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure

router isis instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis 1

Purpose

Enters XR Config mode.

Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.

Note You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.

Enters interface configuration mode.

Step 3 interface type interface-path-id

Example:

RP/0/RP0/CPU0:router(config-isis)# interface

GigabitEthernet0/0/2/1

Step 4

Step 5 address-family ipv4 [ unicast ]

Example:

RP/0/RP0/CPU0:router(config-isis-if)# address-family ipv4 unicast fast-reroute per-prefix

Example:

RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix

Step 6 fast-reroute per-prefix ti-lfa

Example:

Specifies the IPv4 address family, and enters router address family configuration mode.

Enables per-prefix fast reroute.

Enables per-prefix TI-LFA fast reroute link protection.

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Configuring TI-LFA for OSPF

Command or Action

RP/0/RP0/CPU0:router(config-isis-if-af)# fast-reroute per-prefix ti-lfa

Purpose

TI-LFA has been successfully configured for segment routing.

Configuring TI-LFA for OSPF

This task describes how to enable per-prefix Topology Independent Loop-Free Alternate (TI-LFA) computation to converge traffic flows around link failures.

Note TI-LFA can be configured on the instance, area, or interface. When configured on the instance or area, all interfaces in the instance or area inherit the configuration.

Before you begin

Ensure that the following topology requirements are met:

• Router interfaces are configured as per the topology.

• Routers are configured with OSPF.

• Segment routing for OSPF is configured. See

Enabling Segment Routing for OSPF Protocol, on page

23 .

SUMMARY STEPS

configure

router ospf process-name

area area-id

interface type interface-path-id

fast-reroute per-prefix

fast-reroute per-prefix ti-lfa

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure

router ospf process-name

Example:

Purpose

Enters XR Config mode.

Enables OSPF routing for the specified routing process, and places the router in router configuration mode.

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Configuring TI-LFA for OSPF

Step 3

Step 4

Step 5

Step 6

Command or Action

RP/0/RP0/CPU0:router(config)# router ospf 1

area area-id

Example:

RP/0/RP0/CPU0:router(config-ospf)# area 1

interface type interface-path-id

Example:

Purpose

Enters area configuration mode.

Enters interface configuration mode.

RP/0/RP0/CPU0:router(config-ospf-ar)# interface

GigabitEthernet0/0/2/1 fast-reroute per-prefix

Example:

Enables per-prefix fast reroute.

RP/0/RP0/CPU0:router(config-ospf-ar-if)# fast-reroute per-prefix fast-reroute per-prefix ti-lfa

Example:

RP/0/RP0/CPU0:router(config-ospf-ar-if)# fast-reroute per-prefix ti-lfa

Enables per-prefix TI-LFA fast reroute link protection.

TI-LFA has been successfully configured for segment routing.

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Configure Segment Routing Microloop Avoidance

The Segment Routing Microloop Avoidance feature enables link-state routing protocols, such as IS-IS, to prevent or avoid microloops during network convergence after a topology change.

•

About Segment Routing Microloop Avoidance, on page 147

•

Segment Routing Microloop Avoidance Limitations, on page 147

•

Configure Segment Routing Microloop Avoidance for IS-IS, on page 147

•

Configure Segment Routing Microloop Avoidance for OSPF, on page 149

About Segment Routing Microloop Avoidance

Microloops are brief packet loops that occur in the network following a topology change (link down, link up, or metric change events). Microloops are caused by the non-simultaneous convergence of different nodes in the network. If nodes converge and send traffic to a neighbor node that has not converged yet, traffic may be looped between these two nodes, resulting in packet loss, jitter, and out-of-order packets.

The Segment Routing Microloop Avoidance feature detects if microloops are possible following a topology change. If a node computes that a microloop could occur on the new topology, the node creates a loop-free

SR-TE policy path to the destination using a list of segments. After the RIB update delay timer expires, the

SR-TE policy is replaced with regular forwarding paths.

Segment Routing Microloop Avoidance Limitations

For IS-IS, Segment Routing Microloop Avoidance is not supported when incremental shortest path first (ISPF) is configured.

Configure Segment Routing Microloop Avoidance for IS-IS

This task describes how to enable Segment Routing Microloop Avoidance and set the Routing Information

Base (RIB) update delay value for IS-IS.

Before you begin

Ensure that the following topology requirements are met:

• Router interfaces are configured as per the topology.

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Configure Segment Routing Microloop Avoidance for IS-IS

• Routers are configured with IS-IS.

• Segment routing for IS-IS is configured. See

Enabling Segment Routing for IS-IS Protocol, on page 11 .

SUMMARY STEPS

configure

router isis instance-id

address-family ipv4 [ unicast ]

microloop avoidance segment-routing

microloop avoidance rib-update-delay delay-time

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

Step 3

Step 4

Step 5

Purpose

Enters XR Config mode.

RP/0/RP0/CPU0:router# configure

router isis instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis 1

Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.

You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.

Specifies the IPv4 address family and enters router address family configuration mode.

address-family ipv4 [ unicast ]

Example:

RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast microloop avoidance segment-routing

Example:

Enables Segment Routing Microloop Avoidance.

RP/0/RP0/CPU0:router(config-isis-af)# microloop avoidance segment-routing

microloop avoidance rib-update-delay delay-time

Example:

RP/0/RP0/CPU0:router(config-isis-af)# microloop avoidance rib-update-delay 3000

Specifies the amount of time the node uses the microloop avoidance policy before updating its forwarding table. The delay-time is in milliseconds. The range is from 1-60000.

The default value is 5000.

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Configure Segment Routing Microloop Avoidance for OSPF

Configure Segment Routing Microloop Avoidance for OSPF

This task describes how to enable Segment Routing Microloop Avoidance and set the Routing Information

Base (RIB) update delay value for OSPF.

Before you begin

Ensure that the following topology requirements are met:

• Router interfaces are configured as per the topology.

• Routers are configured with OSPF.

• Segment routing for OSPF is configured. See

Enabling Segment Routing for OSPF Protocol, on page

23 .

SUMMARY STEPS

configure

router ospf process-name

microloop avoidance segment-routing

microloop avoidance rib-update-delay delay-time

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure

router ospf process-name

Example:

Step 3

Step 4

RP/0/RP0/CPU0:router(config)# router ospf 1 microloop avoidance segment-routing

Example:

RP/0/RP0/CPU0:router(config-ospf)# microloop avoidance segment-routing

microloop avoidance rib-update-delay delay-time

Example:

RP/0/RP0/CPU0:router(config-ospf)# microloop avoidance rib-update-delay 3000

Purpose

Enters XR Config mode.

Enables OSPF routing for the specified routing process, and places the router in router configuration mode.

Enables Segment Routing Microloop Avoidance.

Specifies the amount of time the node uses the microloop avoidance policy before updating its forwarding table. The delay-time is in milliseconds. The range is from 1-60000.

The default value is 5000.

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Configure Segment Routing Microloop Avoidance

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Configure Segment Routing Mapping Server

The mapping server is a key component of the interworking between LDP and segment routing. It enables

SR-capable nodes to interwork with LDP nodes. The mapping server advertises Prefix-to-SID mappings in

IGP on behalf of other non-SR-capable nodes.

•

Segment Routing Mapping Server, on page 151

•

Segment Routing and LDP Interoperability, on page 152

•

Configuring Mapping Server, on page 154

•

Enable Mapping Advertisement, on page 156

•

Enable Mapping Client, on page 158

Segment Routing Mapping Server

The mapping server functionality in Cisco IOS XR segment routing centrally assigns prefix-SIDs for some or all of the known prefixes. A router must be able to act as a mapping server, a mapping client, or both.

• A router that acts as a mapping server allows the user to configure SID mapping entries to specify the prefix-SIDs for some or all prefixes. This creates the local SID-mapping policy. The local SID-mapping policy contains non-overlapping SID-mapping entries. The mapping server advertises the local

SID-mapping policy to the mapping clients.

• A router that acts as a mapping client receives and parses remotely received SIDs from the mapping server to create remote SID-mapping entries.

• A router that acts as a mapping server and mapping client uses the remotely learnt and locally configured mapping entries to construct the non-overlapping consistent active mapping policy. IGP instance uses the active mapping policy to calculate the prefix-SIDs of some or all prefixes.

The mapping server automatically manages the insertions and deletions of mapping entries to always yield an active mapping policy that contains non-overlapping consistent SID-mapping entries.

• Locally configured mapping entries must not overlap each other.

• The mapping server takes the locally configured mapping policy, as well as remotely learned mapping entries from a particular IGP instance, as input, and selects a single mapping entry among overlapping mapping entries according to the preference rules for that IGP instance. The result is an active mapping policy that consists of non-overlapping consistent mapping entries.

• At steady state, all routers, at least in the same area or level, must have identical active mapping policies.

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Usage Guidelines and Restrictions

Usage Guidelines and Restrictions

• The position of the mapping server in the network is not important. However, since the mapping advertisements are distributed in IGP using the regular IGP advertisement mechanism, the mapping server needs an IGP adjacency to the network.

• The role of the mapping server is crucial. For redundancy purposes, you should configure multiple mapping servers in the networks.

• The mapping server functionality does not support a scenario where SID-mapping entries learned through one IS-IS instance are used by another IS-IS instance to determine the prefix-SID of a prefix. For example, mapping entries learnt from remote routers by 'router isis 1' cannot be used to calculate prefix-SIDs for prefixes learnt, advertised, or downloaded to FIB by 'router isis 2'. A mapping server is required for each

IS-IS instance.

• Segment Routing Mapping Server does not support Virtual Routing and Forwarding (VRF) currently.

Segment Routing and LDP Interoperability

IGP provides mechanisms through which segment routing (SR) interoperate with label distribution protocol

(LDP). The control plane of segment routing co-exists with LDP.

The Segment Routing Mapping Server (SRMS) functionality in SR is used to advertise SIDs for destinations, in the LDP part of the network, that do not support SR. SRMS maintains and advertises segment identifier

(SID) mapping entries for such destinations. IGP propagates the SRMS mapping entries and interacts with

SRMS to determine the SID value when programming the forwarding plane. IGP installs prefixes and corresponding labels, into routing information base (RIB), that are used to program the forwarding information base (FIB).

Example: Segment Routing LDP Interoperability

Consider a network with a mix of segment routing (SR) and label distribution protocol (LDP). A continuous multiprotocol label switching (MPLS) LSP (Labeled Switched Path) can be established by facilitating interoperability. One or more nodes in the SR domain act as segment routing mapping server (SRMS). SRMS advertises SID mappings on behalf of non-SR capable nodes. Each SR-capable node learns about SID assigned to non-SR capable nodes without explicitly configuring individual nodes.

Consider a network as shown in the following image. This network is a mix of both LDP and SR-capable nodes.

In this mixed network:

• Nodes P6, P7, P8, PE4 and PE3 are LDP-capable

• Nodes PE1, PE2, P5 and P6 are SR-capable

• Nodes PE1, PE2, P5 and P6 are configured with segment routing global block (SRGB) of (100, 200)

• Nodes PE1, PE2, P5 and P6 are configured with node segments of 101, 102, 105 and 106 respectively

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Example: Segment Routing LDP Interoperability

A service flow must be established from PE1 to PE3 over a continuous MPLS tunnel. This requires SR and

LDP to interoperate.

LDP to SR

The traffic flow from LDP to SR (right to left) involves:

PE3 learns a service route whose nhop is PE1. PE3 has an LDP label binding from the nhop P8 for the

FEC PE1. PE3 forwards the packet P8.

P8 has an LDP label binding from its nhop P7 for the FEC PE1. P8 forwards the packet to P7.

P7 has an LDP label binding from its nhop P6 for the FEC PE1. P7 forwards the packet to P6.

P6 does not have an LDP binding from its nhop P5 for the FEC PE1. But P6 has an SR node segment to the IGP route PE1. P6 forwards the packet to P5 and swaps its local LDP label for FEC PE1 by the equivalent node segment 101. This process is called label merging.

P5 pops 101, assuming PE1 has advertised its node segment 101 with the penultimate-pop flag set and forwards to PE1.

PE1 receives the tunneled packet and processes the service label.

The end-to-end MPLS tunnel is established from an LDP LSP from PE3 to P6 and the related node segment from P6 to PE1.

SR to LDP

Suppose that the operator configures P5 as a Segment Routing Mapping Server (SRMS) and advertises the mappings (P7, 107), (P8, 108), (PE3, 103) and (PE4, 104). If PE3 was SR-capable, the operator may have configured PE3 with node segment 103. Because PE3 is non-SR capable, the operator configures that policy at the SRMS; the SRMS advertises the mapping on behalf of the non-SR capable nodes. Multiple SRMS servers can be provisioned in a network for redundancy. The mapping server advertisements are only understood by the SR-capable nodes. The SR capable routers install the related node segments in the MPLS data plane in exactly the same manner if node segments were advertised by the nodes themselves.

The traffic flow from SR to LDP (left to right) involves:

PE1 installs the node segment 103 with nhop P5 in exactly the same manner if PE3 had advertised node segment 103.

P5 swaps 103 for 103 and forwards to P6.

The nhop for P6 for the IGP route PE3 is non-SR capable. (P7 does not advertise the SR capability.)

However, P6 has an LDP label binding from that nhop for the same FEC. (For example, LDP label 103.)

P6 swaps 103 for 103 and forwards to P7. We refer to this process as label merging.

P7 swaps this label with the LDP label received from P8 and forwards to P8.

P8 pops the LDP label and forwards to PE3.

PE3 receives the packet and processes as required.

The end-to-end MPLS LSP is established from an SR node segment from PE1 to P6 and an LDP LSP from

P6 to PE3.

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Configuring Mapping Server

Configuring Mapping Server

Perform these tasks to configure the mapping server and to add prefix-SID mapping entries in the active local mapping policy.

SUMMARY STEPS

configure

segment-routing

mapping-server

prefix-sid-map

address-family ipv4 | ipv6

ip-address / prefix-length first-SID-value range range

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure segment-routing

Example:

RP/0/RP0/CPU0:router(config)# segment-routing

Purpose

Enters XR Config mode.

Enables segment routing.

Step 3

Step 4

Step 5 mapping-server

Example:

Enables mapping server configuration mode.

RP/0/RP0/CPU0:router(config-sr)# mapping-server prefix-sid-map

Example:

RP/0/RP0/CPU0:router(config-sr-ms)# prefix-sid-map

Enables prefix-SID mapping configuration mode.

Note Two-way prefix SID can be enabled directly under IS-IS or through a mapping server.

Configures address-family for IS-IS.

address-family ipv4 | ipv6

Example:

This example shows the address-family for ipv4:

RP/0/RP0/CPU0:router(config-sr-ms-map)# address-family ipv4

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Configuring Mapping Server

Step 6

Step 7

Command or Action

This example shows the address-family for ipv6:

Purpose

RP/0/RP0/CPU0:router(config-sr-ms-map)# address-family ipv6 ip-address / prefix-length first-SID-value range range

Example:

RP/0/RP0/CPU0:router(config-sr-ms-map-af)#

10.1.1.1/32 10 range 200

RP/0/RP0/CPU0:router(config-sr-ms-map-af)#

20.1.0.0/16 400 range 300

Adds SID-mapping entries in the active local mapping policy. In the configured example:

• Prefix 10.1.1.1/32 is assigned prefix-SID 10, prefix

10.1.1.2/32 is assigned prefix-SID 11,…, prefix

10.1.1.199/32 is assigned prefix-SID 200

• Prefix 20.1.0.0/16 is assigned prefix-SID 400, prefix

20.2.0.0/16 is assigned prefix-SID 401,…, and so on.

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

Verify information about the locally configured prefix-to-SID mappings.

Note Specify the address family for IS-IS.

RP/0/RP0/CPU0:router# show segment-routing mapping-server prefix-sid-map ipv4

Prefix SID Index Range Flags

20.1.1.0/24

10.1.1.1/32

400

300

200

Number of mapping entries: 2

RP/0/RP0/CPU0:router# show segment-routing mapping-server prefix-sid-map ipv4 detail

Prefix

20.1.1.0/24

SID Index:

Range:

400

300

Last Prefix: 20.2.44.0/24

Last SID Index: 699

Flags:

10.1.1.1/32

SID Index:

Range:

Last Prefix:

200

10.1.1.200/32

Last SID Index: 209

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Enable Mapping Advertisement

Flags:

Number of mapping entries: 2

What to do next

Enable the advertisement of the local SID-mapping policy in the IGP.

Enable Mapping Advertisement

In addition to configuring the static mapping policy, you must enable the advertisement of the mappings in the IGP.

Perform these steps to enable the IGP to advertise the locally configured prefix-SID mapping.

Configure Mapping Advertisement for IS-IS

SUMMARY STEPS

router isis instance-id

address-family { ipv4 | ipv6 } [ unicast ]

segment-routing prefix-sid-map advertise-local

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action

router isis instance-id

Example:

RP/0/RP0/CPU0:router(config)# router isis 1

Purpose

Enables IS-IS routing for the specified routing instance, and places the router in router configuration mode.

• You can change the level of routing to be performed by a particular routing instance by using the is-type router configuration command.

Step 2 address-family { ipv4 | ipv6 } [ unicast ]

Example:

The following is an example for ipv4 address family:

Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.

Step 3

RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast segment-routing prefix-sid-map advertise-local

Example:

Configures IS-IS to advertise locally configured prefix-SID mappings.

RP/0/RP0/CPU0:router(config-isis-af)# segment-routing prefix-sid-map advertise-local

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Configure Segment Routing Mapping Server

Configure Mapping Advertisement for OSPF

Step 4

Command or Action

Use the commit or end command.

Purpose commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

Verify IS-IS prefix-SID mapping advertisement and TLV.

RP/0/RP0/CPU0:router# show isis database verbose

<...removed...>

SID Binding: 10.1.1.1/32 F:0 M:0 S:0 D:0 A:0 Weight:0 Range:200

SID: Start:10 , Algorithm:0, R:0 N:0 P:0 E:0 V:0 L:0

SID Binding: 20.1.1.0/24 F:0 M:0 S:0 D:0 A:0 Weight:0 Range:300

SID: Start:400 , Algorithm:0, R:0 N:0 P:0 E:0 V:0 L:0

Configure Mapping Advertisement for OSPF

SUMMARY STEPS

router ospf process-name

segment-routing prefix-sid-map advertise-local

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action

router ospf process-name

Example:

Step 2

Step 3

RP/0/RP0/CPU0:router(config)# router ospf 1 segment-routing prefix-sid-map advertise-local

Example:

Purpose

Enables OSPF routing for the specified routing instance, and places the router in router configuration mode.

Configures OSPF to advertise locally configured prefix-SID mappings.

RP/0/RP0/CPU0:router(config-ospf)# segment-routing prefix-sid-map advertise-local

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

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Enable Mapping Client

Command or Action Purpose end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

Verify OSP prefix-SID mapping advertisement and TLV.

RP/0/RP0/CPU0:router# show ospf database opaque-area

<...removed...>

Extended Prefix Range TLV: Length: 24

AF : 0

Prefix : 10.1.1.1/32

Range Size: 200

Flags : 0x0

SID sub-TLV: Length: 8

Flags

MTID

: 0x60

: 0

Algo : 0

SID Index : 10

Enable Mapping Client

By default, mapping client functionality is enabled.

You can disable the mapping client functionality by using the segment-routing prefix-sid-map receive disable command.

You can re-enable the mapping client functionality by using the segment-routing prefix-sid-map receive command.

The following example shows how to enable the mapping client for IS-IS:

RP/0/RP0/CPU0:router(config)# router isis 1

RP/0/RP0/CPU0:router(config-isis)# address-family ipv4 unicast

RP/0/RP0/CPU0:router(config-isis-af)# segment-routing prefix-sid-map receive

The following example shows how to enable the mapping client for OSPF:

RP/0/RP0/CPU0:router(config)# router ospf 1

RP/0/RP0/CPU0:router(config-ospf)# segment-routing prefix-sid-map receive

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Using Segment Routing Traffic Matrix

This module provides information about the Segment Routing Traffic Matrix (SR-TM) and the Traffic Collector process, and describes how to configure the TM border and the Traffic Collector and to display traffic information.

•

Segment Routing Traffic Matrix, on page 159

•

Traffic Collector Process, on page 159

•

Configuring Traffic Collector, on page 160

•

Displaying Traffic Information, on page 162

Segment Routing Traffic Matrix

A network's traffic matrix is a description, measure, or estimation of the aggregated traffic flows that enter, traverse, and leave a network.

The Segment Routing Traffic Matrix (SR-TM) is designed to help users understand traffic patterns on a router.

The Traffic Matrix border divides the network into two parts: internal (interfaces that are inside the border) and external (interfaces that are outside the border). By default, all interfaces are internal. You can configure an interface as external.

Traffic Collector Process

The Traffic Collector collects packet and byte statistics from router components such as prefix counters, tunnel counters, and the TM counter. The TM counter increments when traffic that comes from an external interface to the network is destined for a segment routing prefix-SID. The Traffic Collector keeps histories of the statistics and makes them persistent across process restarts, failovers, and ISSU. Histories are retained for a configurable length of time.

Pcounters

A Pcounter is a packet and byte pair of counters. There is one Pcounter per tunnel. There are two Pcounters per prefix-SID:

• Base Pcounter – any packet that is switched on the prefix-SID forwarding information base (FIB) entry

• TM Pcounter – any packet from an external interface and switched on the prefix-SID FIB entry

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Configuring Traffic Collector

The Traffic Collector periodically collects the Base Pcounters and TM Pcounters of all prefix-SIDs, and the

Pcounters of all tunnel interfaces.

For each Pcounter, the Traffic Collector calculates the number of packets and bytes that have been forwarded during the last interval. The Traffic Collector keeps a history of the per-interval statistics for each of the

Pcounters. Each entry in the history contains:

• The start and end time of the interval

• The number of packets forwarded during the interval

• The number of bytes forwarded during the interval

Feature Support and Limitations

• Pcounters for IPv4 SR Prefix SIDs are supported.

• Pcounters for IPv6 SR Prefix SIDs are not supported.

• TM Pcounters increment for incoming SR-labeled and IP traffic destined for an SR Prefix SID.

• External interface support can be enabled on all Ethernet interfaces except Management, Bundle, and sub interfaces. Tunnels may not be set as external interfaces.

• Default VRF is supported. Non-default VRF is not supported.

Configuring Traffic Collector

Perform these tasks to configure the traffic collector.

SUMMARY STEPS

configure

traffic-collector

statistics collection-interval value

statistics history-size value

statistics history-timeout value

interface type l3-interface-address

Use the commit or end command.

DETAILED STEPS

Step 1

Command or Action configure

Example:

Step 2

RP/0/RP0/CPU0:router# configure traffic-collector

Example:

Purpose

Enters XR Config mode.

Enables traffic collector and places the router in traffic collector configuration mode.

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Configuring Traffic Collector

Step 3

Step 4

Step 5

Step 6

Step 7

Command or Action

RP/0/RP0/CPU0:router(config)# traffic-collector

Purpose

statistics collection-interval value

Example:

RP/0/RP0/CPU0:router(config-tc)# statistics collection-interval 5

(Optional) Sets the frequency that the traffic collector collects and posts data, in minutes. Valid values are 1, 2,

3, 4, 5, 6, 10, 12,15, 20, 30, and 60. The default interval is

statistics history-size value

Example:

RP/0/RP0/CPU0:router(config-tc)# statistics history-size 10

(Optional) Specifies the number of entries kept in the history database. Valid values are from 1 to 10. The default is 5.

Note The number of entries affects how the average packet and average byte rates are calculated. The rates are calculated over the range of the histories and are not averages based in real time.

statistics history-timeout value

Example:

RP/0/RP0/CPU0:router(config-tc)# statistics history-timeout 24

(Optional) When a prefix SID or a tunnel-te interface is deleted, the history-timeout sets the length of time, in hours, that the prefix SID and tunnel statistics are retained in the history before they are removed. The minimum is one hour; the maximum is 720 hours. The default is 48.

Note Enter 0 to disable the history timeout. (No history is retained.)

interface type l3-interface-address

Example:

RP/0/RP0/CPU0:router(config-tc)# interface TenGigE

0/1/0/3

Identifies interfaces that handle external traffic. Only L3 interfaces are supported for external traffic.

Use the commit or end command.

commit —Saves the configuration changes and remains within the configuration session.

end —Prompts user to take one of these actions:

• Yes — Saves configuration changes and exits the configuration session.

• No —Exits the configuration session without committing the configuration changes.

• Cancel —Remains in the configuration session, without committing the configuration changes.

This completes the configuration for the traffic collector.

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Displaying Traffic Information

Displaying Traffic Information

The following show commands display information about the interfaces and tunnels:

Note For detailed information about the command syntax for the following show commands, see the Segment

Routing Command Reference Guide .

• Display the configured external interfaces:

RP/0/RSP0/CPU0:router# show traffic-collector external-interface

Interface Status

-----------------------------------

Te0/1/0/3 Enabled

Te0/1/0/4 Enabled

• Display the counter history database for a prefix-SID:

RP/0/RSP0/CPU0:router# show traffic-collector ipv4 counters prefix 1.1.1.10/32 detail

Prefix: 1.1.1.10/32 Label: 16010 State: Active

Base :

Average over the last 5 collection intervals :

Packet rate: 9496937 pps, Byte rate: 9363979882 Bps

History of counters:

23:01 - 23:02 : Packets 9379529, Bytes: 9248215594

23:00 - 23:01: Packets 9687124, Bytes: 9551504264

22:59 - 23:00: Packets 9539200, Bytes: 9405651200

22:58 - 22:59: Packets 9845278, Bytes: 9707444108

22:57 - 22:58: Packets 9033554, Bytes: 8907084244

TM Counters :

Average over the last 5 collection intervals :

Packet rate: 9528754 pps, Byte rate: 9357236821 Bps

History of counters:

23:01 - 23:02: Packets 9400815, Bytes: 9231600330

23:00 - 23:01: Packets 9699455, Bytes: 9524864810

22:59 - 23:00: Packets 9579889, Bytes: 9407450998

22:58 - 22:59: Packets 9911734, Bytes: 9733322788

22:57 - 22:58: Packets 9051879, Bytes: 8888945178

This output shows the average Pcounter (packets, bytes), the Pcounter history, and the collection interval of the Base and TM for the specified prefix-SID.

• Display the counter history database for a policy:

RP/0/RSP0/CPU0:router# show traffic-collector counters tunnels srte_c_12_ep_6.6.6.2

detail

Tunnel: srte_c_12_ep_6.6.6.2

State: Active

Average over the last 5 collection intervals :

Packet rate: 9694434 pps, Byte rate: 9597489858 Bps

History of counters:

23:14 – 23:15 : Packets 9870522 , Bytes: 9771816780

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Displaying Traffic Information

23:13 – 23:14: Packets 9553048 , Bytes: 9457517520

23:12 – 23:13: Packets 9647265 , Bytes: 9550792350

23:11 – 23:12: Packets 9756654 , Bytes: 9659087460

23:10 – 23:11: Packets 9694434 , Bytes: 9548235180

This output shows the average Pcounter (packets, bytes), the Pcounter history, and the collection interval for the policy.

Configuring Telemetry Session to Export SR-TM Statistics

The following configuration shows how to enable the SR-TM and the corresponding model-driven streaming

Telemetry paths for exporting SR-TM statistics. Refer to the Telemetry Configuration Guide for Cisco NCS

6000 Series Routers for details on telemetry.

/* Configure the SR-TM */ traffic-collector interface TenGigE0/3/0/0/8

statistics history-size 10 history-timeout 1

/* Configure streaming telemetry */ telemetry model-driven destination-group test-collector-1 address-family ipv4 10.1.201.250 port 1624

encoding self-describing-gpb protocol tcp

destination-group test-collector-2

address-family ipv4 10.30.110.147 port 31500 encoding self-describing-gpb protocol tcp

/* Configure telemetry paths for SR-TM */ sensor-group test-sg-SRTM sensor-path Cisco-IOS-XR-infra-tc-oper:traffic-collector/summary sensor-path Cisco-IOS-XR-infra-tc-oper:traffic-collector/afs/af/counters/tunnels/tunnel sensor-path Cisco-IOS-XR-infra-tc-oper:traffic-collector/afs/af/counters/prefixes/prefix sensor-path

Cisco-IOS-XR-infra-tc-oper:traffic-collector/external-interfaces/external-interface sensor-path

Cisco-IOS-XR-infra-tc-oper:traffic-collector/vrf-table/default-vrf/afs/af/counters/tunnels/tunnel sensor-path

Cisco-IOS-XR-infra-tc-oper:traffic-collector/vrf-table/default-vrf/afs/af/counters/prefixes/prefix

subscription test-subscription sensor-group-id test-sg-SRTM sample-interval 60000 destination-id test-collector-1 destination-id test-collector-2

source-interface Loopback0

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Using Segment Routing Traffic Matrix

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C H A P T E R

Using Segment Routing OAM

Segment Routing Operations, Administration, and Maintenance (OAM) helps service providers to monitor label-switched paths (LSPs) and quickly isolate forwarding problems to assist with fault detection and troubleshooting in the network. The Segment Routing OAM feature provides support for BGP prefix SIDs,

Nil-FEC (forwarding equivalence classes) LSP Ping and Traceroute functionality.

•

MPLS Ping and Traceroute for BGP and IGP Prefix-SID, on page 165

•

Examples: MPLS Ping, Traceroute, and Tree Trace for Prefix-SID, on page 166

•

MPLS LSP Ping and Traceroute Nil FEC Target, on page 167

•

Examples: LSP Ping and Traceroute for Nil_FEC Target , on page 168

•

Segment Routing Ping and Traceroute, on page 169

•

Segment Routing Data Plane Monitoring , on page 174

MPLS Ping and Traceroute for BGP and IGP Prefix-SID

MPLS Ping and Traceroute operations for Prefix SID are supported for various BGP and IGP scenarios, for example:

• Within an IS-IS level or OSPF area

• Across IS-IS levels or OSPF areas

• Route redistribution from IS-IS to OSPF and from OSPF to IS-IS

• Anycast Prefix SID

• Combinations of BGP and LDP signaled LSPs

The MPLS LSP Ping feature is used to check the connectivity between ingress Label Switch Routers (LSRs) and egress LSRs along an LSP. MPLS LSP ping uses MPLS echo request and reply messages, similar to

Internet Control Message Protocol (ICMP) echo request and reply messages, to validate an LSP. The destination

IP address of the MPLS echo request packet is different from the address used to select the label stack. The destination IP address is defined as a 127.x.y.z/8 address and it prevents the IP packet from being IP switched to its destination, if the LSP is broken.

The MPLS LSP Traceroute feature is used to isolate the failure point of an LSP. It is used for hop-by-hop fault localization and path tracing. The MPLS LSP Traceroute feature relies on the expiration of the Time to

Live (TTL) value of the packet that carries the echo request. When the MPLS echo request message hits a transit node, it checks the TTL value and if it is expired, the packet is passed to the control plane, else the

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Examples: MPLS Ping, Traceroute, and Tree Trace for Prefix-SID message is forwarded. If the echo message is passed to the control plane, a reply message is generated based on the contents of the request message.

The MPLS LSP Tree Trace (traceroute multipath) operation is also supported for BGP and IGP Prefix SID.

MPLS LSP Tree Trace provides the means to discover all possible equal-cost multipath (ECMP) routing paths of an LSP to reach a destination Prefix SID. It uses multipath data encoded in echo request packets to query for the load-balancing information that may allow the originator to exercise each ECMP. When the packet

TTL expires at the responding node, the node returns the list of downstream paths, as well as the multipath information that can lead the operator to exercise each path in the MPLS echo reply. This operation is performed repeatedly for each hop of each path with increasing TTL values until all ECMP are discovered and validated.

MPLS echo request packets carry Target FEC Stack sub-TLVs. The Target FEC sub-TLVs are used by the responder for FEC validation. The BGP and IGP IPv4 prefix sub-TLV has been added to the Target FEC

Stack sub-TLV. The IGP IPv4 prefix sub-TLV contains the prefix SID, the prefix length, and the protocol

(IS-IS or OSPF). The BGP IPv4 prefix sub-TLV contains the prefix SID and the prefix length.

Examples: MPLS Ping, Traceroute, and Tree Trace for Prefix-SID

These examples use the following topology:

MPLS Ping for Prefix-SID

RP/0/RP0/CPU0:router-arizona# ping mpls ipv4 1.1.1.4/32

Thu Dec 17 01:01:42.301 PST

Sending 5, 100-byte MPLS Echos to 1.1.1.4, timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms

MPLS Traceroute for Prefix-SID

RP/0/RP0/CPU0:router-arizona# traceroute mpls ipv4 1.1.1.4/32

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MPLS LSP Ping and Traceroute Nil FEC Target

Thu Dec 17 14:45:05.563 PST

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

0 12.12.12.1 MRU 4470 [Labels: 16004 Exp: 0]

L 1 12.12.12.2 MRU 4470 [Labels: 16004 Exp: 0] 3 ms

L 2 23.23.23.3 MRU 4470 [Labels: implicit-null Exp: 0] 3 ms

! 3 34.34.34.4 11 ms

MPLS Tree Trace for Prefix-SID

RP/0/RP0/CPU0:router-arizona# traceroute mpls multipath ipv4 1.1.1.4/32

Thu Dec 17 14:55:46.549 PST

Starting LSP Path Discovery for 1.1.1.4/32

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

LL!

Path 0 found, output interface TenGigE0/0/0/0 nexthop 12.12.12.2

source 12.12.12.1 destination 127.0.0.0

Path 1 found, output interface TenGigE0/0/0/0 nexthop 12.12.12.2

source 12.12.12.1 destination 127.0.0.2

LL!

Path 2 found, output interface TenGigE0/0/0/1 nexthop 15.15.15.5

source 15.15.15.1 destination 127.0.0.1

Path 3 found, output interface TenGigE0/0/0/1 nexthop 15.15.15.5

source 15.15.15.1 destination 127.0.0.0

Paths (found/broken/unexplored) (4/0/0)

Echo Request (sent/fail) (10/0)

Echo Reply (received/timeout) (10/0)

Total Time Elapsed 53 ms

MPLS LSP Ping and Traceroute Nil FEC Target

The Nil-FEC LSP ping and traceroute operations are extensions of regular MPLS ping and traceroute.

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Examples: LSP Ping and Traceroute for Nil_FEC Target

Nil-FEC LSP Ping/Traceroute functionality supports segment routing and MPLS Static. It also acts as an additional diagnostic tool for all other LSP types. This feature allows operators to provide the ability to freely test any label stack by allowing them to specify the following:

• label stack

• outgoing interface

• nexthop address

In the case of segment routing, each segment nodal label and adjacency label along the routing path is put into the label stack of an echo request message from the initiator Label Switch Router (LSR); MPLS data plane forwards this packet to the label stack target, and the label stack target sends the echo message back.

The following table shows the syntax for the ping and traceroute commands.

Table 6: LSP Ping and Traceroute Nil FEC Commands

Command Syntax ping mpls nil-fec labels { label [ ,label ]} [ output { interface tx-interface } [ nexthop nexthop-ip-addr ]] traceroute mpls nil-fec labels { label [ ,label ]} [ output { interface tx-interface } [ nexthop nexthop-ip-addr ]]

Examples: LSP Ping and Traceroute for Nil_FEC Target

These examples use the following topology:

Node loopback IP address: 172.18.1.3

172.18.1.4

172.18.1.5

172.18.1.7

Node label: 16004 16005 16007

Nodes: Arizona ---- Utah ------- Wyoming ---- Texas

Interface:

Interface IP address:

GigabitEthernet0/2/0/1 GigabitEthernet0/2/0/1

10.1.1.3

10.1.1.4

RP/0/RP0/CPU0:router-utah# show mpls forwarding

Tue Jul 5 13:44:31.999 EDT

Local

Label

Outgoing

Label

Prefix or ID

Outgoing

Interface

Next Hop Bytes

Switched

------ ----------- ------------------ ------------ --------------- ------------

16004 Pop No ID Gi0/2/0/1 10.1.1.4

1392

Pop

16005 16005

16005

16007 16007

16007

No ID

Gi0/2/0/2

Gi0/2/0/0

Gi0/2/0/1

Gi0/2/0/0

Gi0/2/0/1

10.1.2.2

10.1.1.4

10.1.2.2

10.1.1.4

10.1.2.2

4752

24000 Pop

24001 Pop

24002 Pop

24003 Pop

24004 Pop

24005 Pop

24006 Pop

24007 Pop

SR Adj (idx 0)

SR Adj (idx 2)

SR Adj (idx 0)

SR Adj (idx 2)

No ID

Gi0/2/0/0

Gi0/2/0/1

Gi0/2/0/1 tt10 tt11 tt12 tt13

10.1.1.4

10.1.2.2

point2point point2point point2point point2point

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Segment Routing Ping and Traceroute

24008 Pop No ID tt30 point2point 0

Ping Nil FEC Target

RP/0/RP0/CPU0:router-arizona# ping mpls nil-fec labels 16005,16007 output interface

GigabitEthernet 0/2/0/1 nexthop 10.1.1.4 repeat 1

Sending 1, 72-byte MPLS Echos with Nil FEC labels 16005,16007, timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'd' - see DDMAP for return code,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

Success rate is 100 percent (1/1), round-trip min/avg/max = 1/1/1 ms

Total Time Elapsed 0 ms

Traceroute Nil FEC Target

RP/0/RP0/CPU0:router-arizona# traceroute mpls nil-fec labels 16005,16007 output interface

GigabitEthernet 0/2/0/1 nexthop 10.1.1.4

Tracing MPLS Label Switched Path with Nil FEC labels 16005,16007, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no label entry,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'd' - see DDMAP for return code,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

0 10.1.1.3 MRU 1500 [Labels: 16005/16007/explicit-null Exp: 0/0/0]

L 1 10.1.1.4 MRU 1500 [Labels: implicit-null/16007/explicit-null Exp: 0/0/0] 1 ms

L 2 10.1.1.5 MRU 1500 [Labels: implicit-null/explicit-null Exp: 0/0] 1 ms

! 3 10.1.1.7 1 ms

Segment Routing Ping and Traceroute

Segment Routing Ping

The MPLS LSP ping feature is used to check the connectivity between ingress and egress of LSP. MPLS LSP ping uses MPLS echo request and reply messages, similar to Internet Control Message Protocol (ICMP) echo request and reply messages, to validate an LSP. Segment routing ping is an extension of the MPLS LSP ping to perform the connectivity verification on the segment routing control plane.

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Segment Routing Ping

Note Segment routing ping can only be used when the originating device is running segment routing.

You can initiate the segment routing ping operation only when Segment Routing control plane is available at the originator, even if it is not preferred. This allows you to validate the SR path before directing traffic over the path. Segment Routing ping can use either generic FEC type or SR control-plane FEC type (SR-OSPF,

SR-ISIS). In mixed networks, where some devices are running MPLS control plane (for example, LDP) or do not understand SR FEC, generic FEC type allows the device to successfully process and respond to the echo request. By default, generic FEC type is used in the target FEC stack of segment routing ping echo request. Generic FEC is not coupled to a particular control plane; it allows path verification when the advertising protocol is unknown or might change during the path of the echo request. If you need to specify the target

FEC, you can select the FEC type as OSPF, IS-IS, or BGP. This ensures that only devices that are running segment routing control plane, and can therefore understand the segment routing IGP FEC, respond to the echo request.

Configuration Examples

These examples show how to use segment routing ping to test the connectivity of a segment routing control plane. In the first example, FEC type is not specified. You can also specify the FEC type as shown in the other examples.

RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32

Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/5 ms

RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32 fec-type generic

Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms

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Segment Routing Traceroute

RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32 fec-type igp ospf

Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms

RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32 fec-type igp isis

Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms

RP/0/RP0/CPU0:router# ping sr-mpls 10.1.1.2/32 fec-type bgp

Sending 5, 100-byte MPLS Echos to 10.1.1.2/32, timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms

Segment Routing Traceroute

The MPLS LSP traceroute is used to isolate the failure point of an LSP. It is used for hop-by-hop fault localization and path tracing. The MPLS LSP traceroute feature relies on the expiration of the Time to Live

(TTL) value of the packet that carries the echo request. When the MPLS echo request message hits a transit

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Segment Routing Traceroute node, it checks the TTL value and if it is expired, the packet is passed to the control plane, else the message is forwarded. If the echo message is passed to the control plane, a reply message is generated based on the contents of the request message. Segment routing traceroute feature extends the MPLS LSP traceroute functionality to segment routing networks.

Similar to segment routing ping, you can initiate the segment routing traceroute operation only when Segment

Routing control plane is available at the originator, even if it is not preferred. Segment Routing traceroute can use either generic FEC type or SR control-plane FEC type (SR-OSPF, SR-ISIS). By default, generic FEC type is used in the target FEC stack of segment routing traceroute echo request. If you need to specify the target FEC, you can select the FEC type as OSPF, IS-IS, or BGP. This ensures that only devices that are running segment routing control plane, and can therefore understand the segment routing IGP FEC, respond to the echo request.

The existence of load balancing at routers in an MPLS network provides alternate paths for carrying MPLS traffic to a target router. The multipath segment routing traceroute feature provides a means to discover all possible paths of an LSP between the ingress and egress routers.

Configuration Examples

These examples show how to use segment routing traceroute to trace the LSP for a specified IPv4 prefix SID address. In the first example, FEC type is not specified. You can also specify the FEC type as shown in the other examples.

RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32

Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]

! 1 10.12.12.2 3 ms

RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32 fec-type generic

Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]

! 1 10.12.12.2 2 ms

RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32 fec-type igp ospf

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Segment Routing Traceroute

Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]

! 1 10.12.12.2 2 ms

RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32 fec-type igp isis

Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]

! 1 10.12.12.2 2 ms

RP/0/RP0/CPU0:router# traceroute sr-mpls 10.1.1.2/32 fec-type bgp

Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

0 10.12.12.1 MRU 1500 [Labels: implicit-null/implicit-null Exp: 0/0]

! 1 10.12.12.2 2 ms

This example shows how to use multipath traceroute to discover all the possible paths for a IPv4 prefix SID.

RP/0/RP0/CPU0:router# traceroute sr-mpls multipath 10.1.1.2/32

Starting LSP Path Discovery for 10.1.1.2/32

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,

'L' - labeled output interface, 'B' - unlabeled output interface,

'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,

'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,

'P' - no rx intf label prot, 'p' - premature termination of LSP,

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Segment Routing Data Plane Monitoring

'R' - transit router, 'I' - unknown upstream index,

'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

Path 0 found, output interface GigabitEthernet0/0/0/2 nexthop 10.13.13.2

source 10.13.13.1 destination 127.0.0.0

Path 1 found, output interface Bundle-Ether1 nexthop 10.12.12.2

source 10.12.12.1 destination 127.0.0.0

Paths (found/broken/unexplored) (2/0/0)

Echo Request (sent/fail) (2/0)

Echo Reply (received/timeout) (2/0)

Total Time Elapsed 14 ms

Segment Routing Data Plane Monitoring

Unreported traffic drops in MPLS networks could be difficult to detect and isolate. They can be caused by user configuration, out-of-sync neighbors, or incorrect data-plane programming. Segment Routing Data Plane

Monitoring (SR DPM) provides a scalable solution to address data-plane consistency verification and detection of unreported traffic drops. SR DPM validates the actual data plane status of all FIB entries associated with

SR IGP prefix SIDs.

The primary benefits of SR DPM include:

• Automation – A node automatically verifies the integrity of the actual forwarding entries exercised by transit traffic.

• Comprehensive Coverage – Tests validate forwarding consistency for each set of destination prefixes across each combination of upstream and downstream neighbors and across all ECMP possibilities.

• Scalability – SR DPM is a highly scalable solution due to its localized detection process.

• Proactive and Reactive modes of operation – Solution caters to both continuous and on-demand verification.

• Standards-based – SR DPM uses existing MPLS OAM tools and leverages SR to enforce test traffic path.

DPM performs data plane validation in two phases:

• Adjacency Validation—Using special MPLS echo request packets, adjacency validation ensures that all local links are able to forward and receive MPLS traffic correctly from their neighbors. It also ensures that DPM is able to verify all local adjacency SID labels and to flag any inconsistencies, including traffic drops, forwarding by the local or neighboring device to an incorrect neighbor that is not associated with the specified adjacency, or forwarding by the local or neighboring device to the correct neighbor but over an incorrect link not associated with the specified adjacency. DPM validates the following adjacencies for each link when available:

• Unprotected adjacency

• Protected adjacency

• Static adjacency

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• Dynamic adjacency

• Shared adjacency

Note Observe the following limitations for adjacency validation:

• The adjacency validation phase only validates links that are participating in

IGP (OSPF and IS-IS) instances. If one or more link is not part of the IGP, it will not be validated since there are no Adjacency SID labels.

• Adjacency validation only validates physical and bundle links, including broadcast links.

• Prefix Validation—Prefix validation identifies any forwarding inconsistency of any IGP Prefix SID reachable from the device. The validation is done for all upstream and downstream neighbor combinations of each prefix SID, and identifies inconsistencies in the downstream neighbor. The prefix validation phase simulates customer traffic path by validating both ingress and egress forwarding chain at the DPM processing node.

Since prefix validation is localized to a device running DPM as well as its immediate neighbors, it does not suffer from scale limitations of end-to-end monitoring.

Prefix validation builds on top of adjacency validation by using special MPLS echo requests that travel to the upstream node, return to the DPM-processing node, and time-to-live (TTL) expire at the immediate downstream node, thus exercising entire forwarding path towards the downstream.

Note Observe the following limitations for prefix validation:

• Because prefix validation builds on top of adjacency validation, if a link is not part of adjacency validation, it is not used in prefix validation.

• If all adjacencies are marked as “Faulty” during adjacency validation, prefix validation is not performed.

• If a node only has downstream links at a specific node, but no upstream node

(possible in certain PE node scenarios), Prefix Validation is not performed.

• Prefix validation does not support TI-LFA.

DPM maintains a database of all prefixes and adjacencies being monitored.

The prefix database is populated by registering as a redistribution client to RIB, which enables DPM to keep the database up-to-date whenever IGP pushes a new prefix SID to RIB, deletes an existing prefix SID, or when the path of an existing prefix SID is modified.

DPM maintains the following prefix data:

• IPv4 Prefix

• Prefix Length

• Prefix SID label

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• Error stats

DPM also maintains a list of all local adjacencies. DPM maintains a database that contains local links, their respective local and remote adjacency labels and IP addresses, and error stats.

SR-DPM Operation: Example

The following SR-DPM operation example use the following scenarios:

Figure 11: Test Iteration A Path

Figure 12: Test Iteration B Path

Node 2 is a DPM-capable device. DPM is enabled in proactive mode to perform forwarding consistency tests for all prefix-SIDs in the network. For each destination prefix, the router identifies the directly connected upstream and downstream neighbors used to reach a given destination.

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Configure SR DPM

Using node 9 as the prefix under test (prefix-SID = 16009), node 1 is designated as the upstream node and node 3 as the downstream nodes with 2 ECMPs.

Node 2 generates test traffic (MPLS OAM ping with source_ip of node 2) to test its forwarding for every upstream/downstream combination. In this case, two combinations exist:

• Prefix-SID node 9 - test iteration A path = Node 2 to Node 1 to Node 2 to Node 3 (via top ECMP)

• Prefix-SID node 9 - test iteration B path = Node 2 to Node 1 to Node 2 to Node 3 (via bottom ECMP)

Node 2 adds a label stack in order to enforce the desired path for the test traffic. For example, two labels are added to the packet for test iterations A and B:

• The top label is equal to the adjacency-SID on node 1 for the interface facing node 2 (adjacency SID

= 24012). The bottom label is the prefix-SID under test (16009). The test traffic is sent on the interface facing node 1.

• The top label (after being POPed at node 1) causes the test traffic to come back to node 2. This returning traffic is completely hardware-switched based on the forwarding entry for the prefix-SID under test (16009). Note that the labeled test traffic has a time-to-live (TTL) of 2 and it will never be forwarded beyond the downstream router(s).

• When test traffic reaches node 3, a TTL expired response is sent back to node 2. If the response packet arrives over the expected interface ( top ECMP link) then the forwarding verification on node

2 for the first iteration towards node 9 is considered to be a success.

• The difference between the test traffic for test iteration A and B in this example is the destination_ip of the MPLS OAM ping. Node 2 calculates them in this order to exercise a given ECMP path (if present). Thus, test traffic for iteration A is hashed onto the top ECMP and test traffic for iteration

B is hashed onto the bottom ECMP link.

The DPM tests are then repeated for the remaining prefix-SIDs in the network

Configure SR DPM

To configure SR-DPM, complete the following configurations:

• Enable SR DPM

• Configure SR DPM interval timer

• Configure SR DPM rate limit

Enable SR DPM

Use the mpls oam dpm command to enable SR DPM and enter MPLS OAM DPM command mode.

Router(config)# mpls oam dpm

Router(config-oam-dpm)#

Configure SR DPM Interval Timer

Use the interval minutes command in MPLS OAM DPM command mode to specify how often to run DPM scan. The range is from 1 to 3600 minutes. The default is 30 minutes.

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Router(config-oam-dpm)# interval 240

Router(config-oam-dpm#

Configure SR DPM Rate Limit

Use the pps pps command in MPLS OAM DPM command mode to rate limit the number of echo request packets per second (PPS) generated by DPM. The range is from 1 to 250 PPS. The default is 50 PPS.

Note If the specified rate limit is more than the rate limit for overall MPLS OAM requests, DPM generates an error message.

Router(config-oam-dpm)# pps 45

Router(config-oam-dpm#

Verification

Router# show mpls oam dpm summary

Displays the overall status of SR-DPM from the last run.

Router# show mpls oam dpm adjacency summary

Displays the result of DPM adjacency SID verification for all local interfaces from the last run.

Router# show mpls oam dpm adjacency interface

Displays the result of DPM adjacency SID verification for all adjacencies for the specified local interface.

Router# show mpls oam dpm counters

Outputs various counters for DPM from last run as well as since the start of DPM process.

Router# show mpls oam dpm prefix summary

Displays the result of DPM prefix SID verification for all reachable IGP prefix SIDs from the last run.

Router# show mpls oam dpm prefix prefix

Displays the result of DPM prefix SID verification for the specified prefix including all upstream and downstream combinations.

Router# show mpls oam dpm trace

Returns logged traces for DPM.

In addition, the existing show mpls oam command is extended to specify DPM counters.

Router# show mpls oam counters packet dpm

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Reklāma