C H A P T E R
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Configure Segment Routing Microloop Avoidance
The Segment Routing Microloop Avoidance feature enables link-state routing protocols, such as IS-IS and
OSPF, to prevent or avoid microloops during network convergence after a topology change.
•
About Segment Routing Microloop Avoidance, on page 273
•
Configure Segment Routing Microloop Avoidance for IS-IS, on page 273
•
Configure Segment Routing Microloop Avoidance for OSPF, on page 274
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.
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.
• Routers are configured with IS-IS.
• Segment routing for IS-IS is configured. See
Enabling Segment Routing for IS-IS Protocol, on page 61
.
• Enter the following commands in global configuration mode:
Router(config)# ipv4 unnumbered mpls traffic-eng Loopback0
Router(config)# mpls traffic-eng
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Configure Segment Routing Microloop Avoidance
Configure Segment Routing Microloop Avoidance for OSPF
Router(config-mpls-te)# exit
Router(config)#
SUMMARY STEPS
1.
configure
2.
router isis instance-id
3.
address-family ipv4 [ unicast ]
4.
microloop avoidance segment-routing
5.
microloop avoidance rib-update-delay delay-time
DETAILED STEPS
Step 1
Command or Action configure
Example:
Step 2
Step 3
Step 4
Step 5
RP/0/RP0/CPU0:router# configure
router isis instance-id
Example:
RP/0/RP0/CPU0:router(config)# router isis 1
Purpose
Enters global configuration 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 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.
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.
274
Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Configure Segment Routing Microloop Avoidance
Configure Segment Routing Microloop Avoidance 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
81 .
• Enter the following commands in global configuration mode:
Router(config)# ipv4 unnumbered mpls traffic-eng Loopback0
Router(config)# mpls traffic-eng
Router(config-mpls-te)# exit
Router(config)#
SUMMARY STEPS
1.
configure
2.
router ospf process-name
3.
microloop avoidance segment-routing
4.
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
RP/0/RP0/CPU0:router(config)# router ospf 1 microloop avoidance segment-routing
Example:
Step 4
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 global configuration 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 for OSPF
Configure Segment Routing Microloop Avoidance
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Segment Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
