Implementing IPv6 Addressing and Basic Connectivity

Implementing IPv6 Addressing and Basic
Connectivity
First Published: June 7, 2001
Last Updated: May 5, 2009
Implementing basic IPv6 connectivity in the Cisco IOS software consists of assigning IPv6 addresses to
individual router interfaces. The forwarding of IPv6 traffic can be enabled globally, and Cisco Express
Forwarding switching for IPv6 can also be enabled. Basic connectivity can be enhanced by configuring
support for AAAA record types in the Domain Name System (DNS) name-to-address and
address-to-name lookup processes, and by managing IPv6 neighbor discovery.
This module describes IPv6 addressing and basic IPv6 connectivity tasks.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature
information and caveats, see the release notes for your platform and software release. To find information
about the features documented in this module, and to see a list of the releases in which each feature is
supported, see the “Feature Information for Implementing IPv6 Addressing and Basic Connectivity” section
on page 62.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An
account on Cisco.com is not required.
Contents
•
Prerequisites for Implementing IPv6 Addressing and Basic Connectivity, page 2
•
Restrictions for Implementing IPv6 Addressing and Basic Connectivity, page 2
•
Information About Implementing IPv6 Addressing and Basic Connectivity, page 3
•
How to Implement IPv6 Addressing and Basic Connectivity, page 27
•
Configuration Examples for Implementing IPv6 Addressing and Basic Connectivity, page 51
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© 2006–2009 Cisco Systems, Inc. All rights reserved.
Implementing IPv6 Addressing and Basic Connectivity
Prerequisites for Implementing IPv6 Addressing and Basic Connectivity
•
Where to Go Next, page 56
•
Additional References, page 57
•
Command Reference, page 59
•
Feature Information for Implementing IPv6 Addressing and Basic Connectivity, page 62
Prerequisites for Implementing IPv6 Addressing and Basic
Connectivity
•
This document assumes that you are familiar with IPv4. See the publications shown in the
“Additional References” section for IPv4 configuration and command reference information.
•
The following prerequisites apply to Cisco Express Forwarding and distributed Cisco Express
Forwarding for IPv6:
– To forward IPv6 traffic using Cisco Express Forwarding or distributed Cisco Express
Forwarding, you must configure forwarding of IPv6 unicast datagrams globally on the router by
using the ipv6 unicast-routing command, and you must configure an IPv6 address on an
interface by using the ipv6 address command.
– You must enable Cisco Express Forwarding for IPv4 globally on the router by using the ip cef
command before enabling Cisco Express Forwarding for IPv6 globally on the router by using
the ipv6 cef command.
– On distributed architecture platforms that support both Cisco Express Forwarding and
distributed Cisco Express Forwarding, such as the Cisco 7500 series routers, you must enable
distributed Cisco Express Forwarding for IPv4 globally on the router by using the ip cef
distributed command before enabling distributed Cisco Express Forwarding for IPv6 globally
on the router by using the ipv6 cef distributed command.
Note
By default, the Cisco 12000 series Internet routers support only distributed Cisco Express
Forwarding.
– To use Unicast Reverse Path Forwarding (RPF), enable Cisco Express Forwarding switching or
distributed Cisco Express Forwarding switching in the router. There is no need to configure the
input interface for Cisco Express Forwarding switching. As long as Cisco Express Forwarding
is running on the router, individual interfaces can be configured with other switching modes.
Note
For Unicast RPF to work, Cisco Express Forwarding must be configured globally in the router.
Unicast RPF will not work without Cisco Express Forwarding.
Restrictions for Implementing IPv6 Addressing and Basic
Connectivity
•
2
In Cisco IOS Release 12.2(11)T or earlier releases, IPv6 supports only process switching for packet
forwarding. Cisco Express Forwarding switching and distributed Cisco Express Forwarding
switching for IPv6 are supported in Cisco IOS Release 12.2(13)T. Distributed Cisco Express
Forwarding switching for IPv6 is supported in Cisco IOS Release 12.0(21)ST.
Implementing IPv6 Addressing and Basic Connectivity
Information About Implementing IPv6 Addressing and Basic Connectivity
•
IPv6 packets are transparent to Layer 2 LAN switches because the switches do not examine Layer 3
packet information before forwarding IPv6 frames. Therefore, IPv6 hosts can be directly attached
to Layer 2 LAN switches.
•
In any Cisco IOS release with IPv6 support, multiple IPv6 global addresses within the same prefix
can be configured on an interface. However, multiple IPv6 link-local addresses on an interface are
not supported. See the “IPv6 Addressing and IPv6 Routing Configuration: Example” section for
information on configuring multiple IPv6 global addresses within the same prefix on an interface.
•
Because RFC 3879 deprecates the use of site-local addresses, configuration of private IPv6
addresses should be done following the recommendations of unique local addressing (ULA) in
RFC 4193.
Information About Implementing IPv6 Addressing and Basic
Connectivity
To configure IPv6 addressing and basic connectivity for IPv6 for Cisco IOS software, you must
understand the following concepts:
•
IPv6 for Cisco IOS Software, page 4
•
Large IPv6 Address Space for Unique Addresses, page 4
•
IPv6 Address Formats, page 4
•
IPv6 Address Type: Unicast, page 5
•
IPv6 Address Type: Anycast, page 9
•
IPv6 Address Type: Multicast, page 10
•
IPv6 Address Output Display, page 11
•
Simplified IPv6 Packet Header, page 12
•
Cisco Express Forwarding and Distributed Cisco Express Forwarding Switching for IPv6, page 15
•
DNS for IPv6, page 17
•
Path MTU Discovery for IPv6, page 17
•
Cisco Discovery Protocol IPv6 Address Support, page 17
•
ICMP for IPv6, page 18
•
IPv6 Neighbor Discovery, page 18
•
Link, Subnet, and Site Addressing Changes, page 24
•
IPv6 Prefix Aggregation, page 25
•
IPv6 Site Multihoming, page 26
•
IPv6 Data Links, page 26
•
Routed Bridge Encapsulation for IPv6, page 26
•
Dual IPv4 and IPv6 Protocol Stacks, page 26
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Implementing IPv6 Addressing and Basic Connectivity
Information About Implementing IPv6 Addressing and Basic Connectivity
IPv6 for Cisco IOS Software
IPv6, formerly named IPng (next generation), is the latest version of the Internet Protocol (IP). IP is a
packet-based protocol used to exchange data, voice, and video traffic over digital networks. IPv6 was
proposed when it became clear that the 32-bit addressing scheme of IP version 4 (IPv4) was inadequate
to meet the demands of Internet growth. After extensive discussion it was decided to base IPng on IP but
add a much larger address space and improvements such as a simplified main header and extension
headers. IPv6 is described initially in RFC 2460, Internet Protocol, Version 6 (IPv6) Specification,
issued by the Internet Engineering Task Force (IETF). Further RFCs describe the architecture and
services supported by IPv6.
The architecture of IPv6 has been designed to allow existing IPv4 users to transition easily to IPv6 while
providing services such as end-to-end security, quality of service (QoS), and globally unique addresses.
The larger IPv6 address space allows networks to scale and provide global reachability. The simplified
IPv6 packet header format handles packets more efficiently. IPv6 prefix aggregation, simplified network
renumbering, and IPv6 site multihoming capabilities provide an IPv6 addressing hierarchy that allows
for more efficient routing. IPv6 supports widely deployed routing protocols such as Routing Information
Protocol (RIP), Integrated Intermediate System-to-Intermediate System (IS-IS), Open Shortest Path
First for IPv6, and multiprotocol Border Gateway Protocol (BGP). Other available features include
stateless autoconfiguration, enhanced support for Mobile IPv6, and an increased number of multicast
addresses.
Large IPv6 Address Space for Unique Addresses
The primary motivation for IPv6 is the need to meet the anticipated future demand for globally unique
IP addresses. Applications such as mobile Internet-enabled devices (such as personal digital assistants
[PDAs], telephones, and cars), home-area networks (HANs), and wireless data services are driving the
demand for globally unique IP addresses. IPv6 quadruples the number of network address bits from
32 bits (in IPv4) to 128 bits, which provides more than enough globally unique IP addresses for every
networked device on the planet. By being globally unique, IPv6 addresses inherently enable global
reachability and end-to-end security for networked devices, functionality that is crucial to the
applications and services that are driving the demand for the addresses. Additionally, the flexibility of
the IPv6 address space reduces the need for private addresses and the use of Network Address
Translation (NAT); therefore, IPv6 enables new application protocols that do not require special
processing by border routers at the edge of networks.
IPv6 Address Formats
IPv6 addresses are represented as a series of 16-bit hexadecimal fields separated by colons (:) in the
format: x:x:x:x:x:x:x:x. Following are two examples of IPv6 addresses:
2001:0DB8:7654:3210:FEDC:BA98:7654:3210
2001:0DB8:0:0:8:800:200C:417A
It is common for IPv6 addresses to contain successive hexadecimal fields of zeros. To make IPv6
addresses less cumbersome, two colons (::) may be used to compress successive hexadecimal fields of
zeros at the beginning, middle, or end of an IPv6 address (the colons represent successive hexadecimal
fields of zeros). Table 1 lists compressed IPv6 address formats.
A double colon may be used as part of the ipv6-address argument when consecutive 16-bit values are
denoted as zero. You can configure multiple IPv6 addresses per interfaces, but only one link-local
address.
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Note
Two colons (::) can be used only once in an IPv6 address to represent the longest successive hexadecimal
fields of zeros.
The hexadecimal letters in IPv6 addresses are not case-sensitive.
Table 1
Compressed IPv6 Address Formats
IPv6 Address Type
Preferred Format
Compressed Format
Unicast
2001:0:0:0:0DB8:800:200C:417A 2001::0DB8:800:200C:417A
Multicast
FF01:0:0:0:0:0:0:101
FF01::101
Loopback
0:0:0:0:0:0:0:1
::1
Unspecified
0:0:0:0:0:0:0:0
::
The loopback address listed in Table 1 may be used by a node to send an IPv6 packet to itself. The
loopback address in IPv6 functions the same as the loopback address in IPv4 (127.0.0.1).
Note
The IPv6 loopback address cannot be assigned to a physical interface. A packet that has the IPv6
loopback address as its source or destination address must remain within the node that created the packet.
IPv6 routers do not forward packets that have the IPv6 loopback address as their source or destination
address.
The unspecified address listed in Table 1 indicates the absence of an IPv6 address. For example, a newly
initialized node on an IPv6 network may use the unspecified address as the source address in its packets
until it receives its IPv6 address.
Note
The IPv6 unspecified address cannot be assigned to an interface. The unspecified IPv6 addresses must
not be used as destination addresses in IPv6 packets or the IPv6 routing header.
An IPv6 address prefix, in the format ipv6-prefix/prefix-length, can be used to represent bit-wise
contiguous blocks of the entire address space. The ipv6-prefix must be in the form documented in
RFC 2373 where the address is specified in hexadecimal using 16-bit values between colons. The prefix
length is a decimal value that indicates how many of the high-order contiguous bits of the address
comprise the prefix (the network portion of the address). For example, 2001:0DB8:8086:6502::/32 is a
valid IPv6 prefix.
IPv6 Address Type: Unicast
An IPv6 unicast address is an identifier for a single interface, on a single node. A packet that is sent to
a unicast address is delivered to the interface identified by that address. The Cisco IOS software supports
the following IPv6 unicast address types:
•
Aggregatable Global Address, page 6
•
Link-Local Address, page 7
•
IPv4-Compatible IPv6 Address, page 8
•
Unique Local Address, page 8
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Implementing IPv6 Addressing and Basic Connectivity
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Aggregatable Global Address
An aggregatable global address is an IPv6 address from the aggregatable global unicast prefix. The
structure of aggregatable global unicast addresses enables strict aggregation of routing prefixes that
limits the number of routing table entries in the global routing table. Aggregatable global addresses are
used on links that are aggregated upward through organizations, and eventually to the Internet service
providers (ISPs).
Aggregatable global IPv6 addresses are defined by a global routing prefix, a subnet ID, and an
interface ID. Except for addresses that start with binary 000, all global unicast addresses have a 64-bit
interface ID. The IPv6 global unicast address allocation uses the range of addresses that start with binary
value 001 (2000::/3). Figure 1 shows the structure of an aggregatable global address.
3
Aggregatable Global Address Format
Provider
Site
Host
45 bits
16 bits
64 bits
Global Routing Prefix
SLA
Interface ID
88119
Figure 1
001
Addresses with a prefix of 2000::/3 (001) through E000::/3 (111) are required to have 64-bit interface
identifiers in the extended universal identifier (EUI)-64 format. The Internet Assigned Numbers
Authority (IANA) allocates the IPv6 address space in the range of 2000::/16 to regional registries.
The aggregatable global address typically consists of a 48-bit global routing prefix and a 16-bit subnet
ID or Site-Level Aggregator (SLA). In the IPv6 aggregatable global unicast address format document
(RFC 2374), the global routing prefix included two other hierarchically structured fields named
Top-Level Aggregator (TLA) and Next-Level Aggregator (NLA). The IETF decided to remove the TLS
and NLA fields from the RFCs because these fields are policy-based. Some existing IPv6 networks
deployed before the change might still be using networks based on the older architecture.
A 16-bit subnet field called the subnet ID could be used by individual organizations to create their own
local addressing hierarchy and to identify subnets. A subnet ID is similar to a subnet in IPv4, except that
an organization with an IPv6 subnet ID can support up to 65,535 individual subnets.
An interface ID is used to identify interfaces on a link. The interface ID must be unique to the link. It
may also be unique over a broader scope. In many cases, an interface ID will be the same as or based on
the link-layer address of an interface. Interface IDs used in aggregatable global unicast and other IPv6
address types must be 64 bits long and constructed in the modified EUI-64 format.
Interface IDs are constructed in the modified EUI-64 format in one of the following ways:
•
6
For all IEEE 802 interface types (for example, Ethernet, and FDDI interfaces), the first three octets
(24 bits) are taken from the Organizationally Unique Identifier (OUI) of the 48-bit link-layer
address (the Media Access Control [MAC] address) of the interface, the fourth and fifth octets
(16 bits) are a fixed hexadecimal value of FFFE, and the last three octets (24 bits) are taken from the
last three octets of the MAC address. The construction of the interface ID is completed by setting
the Universal/Local (U/L) bit—the seventh bit of the first octet—to a value of 0 or 1. A value of 0
indicates a locally administered identifier; a value of 1 indicates a globally unique IPv6 interface
identifier.
Implementing IPv6 Addressing and Basic Connectivity
Information About Implementing IPv6 Addressing and Basic Connectivity
•
For all other interface types (for example, serial, loopback, ATM, Frame Relay, and tunnel interface
types—except tunnel interfaces used with IPv6 overlay tunnels), the interface ID is constructed in
the same way as the interface ID for IEEE 802 interface types; however, the first MAC address from
the pool of MAC addresses in the router is used to construct the identifier (because the interface does
not have a MAC address).
•
For tunnel interface types that are used with IPv6 overlay tunnels, the interface ID is the IPv4
address assigned to the tunnel interface with all zeros in the high-order 32 bits of the identifier.
Note
For interfaces using Point-to-Point Protocol (PPP), given that the interfaces at both ends of the
connection might have the same MAC address, the interface identifiers used at both ends of the
connection are negotiated (picked randomly and, if necessary, reconstructed) until both
identifiers are unique. The first MAC address in the router is used to construct the identifier for
interfaces using PPP.
If no IEEE 802 interface types are in the router, link-local IPv6 addresses are generated on the interfaces
in the router in the following sequence:
1.
The router is queried for MAC addresses (from the pool of MAC addresses in the router).
2.
If no MAC addresses are available in the router, the serial number of the router is used to form the
link-local addresses.
3.
If the serial number of the router cannot be used to form the link-local addresses, the router uses a
Message Digest algorithm 5 (MD5) hash to determine the MAC address of the router from the
hostname of the router.
Link-Local Address
A link-local address is an IPv6 unicast address that can be automatically configured on any interface
using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64
format. Link-local addresses are used in the neighbor discovery protocol and the stateless
autoconfiguration process. Nodes on a local link can use link-local addresses to communicate; the nodes
do not need globally unique addresses to communicate. Figure 2 shows the structure of a link-local
address.
IPv6 routers must not forward packets that have link-local source or destination addresses to other links.
Figure 2
Link-Local Address Format
128 bits
0
Interface ID
FE80::/10
10 bits
52669
1111 1110 10
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Implementing IPv6 Addressing and Basic Connectivity
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IPv4-Compatible IPv6 Address
An IPv4-compatible IPv6 address is an IPv6 unicast address that has zeros in the high-order 96 bits of
the address and an IPv4 address in the low-order 32 bits of the address. The format of an IPv4-compatible
IPv6 address is 0:0:0:0:0:0:A.B.C.D or ::A.B.C.D. The entire 128-bit IPv4-compatible IPv6 address is
used as the IPv6 address of a node and the IPv4 address embedded in the low-order 32 bits is used as the
IPv4 address of the node. IPv4-compatible IPv6 addresses are assigned to nodes that support both the
IPv4 and IPv6 protocol stacks and are used in automatic tunnels. Figure 3 shows the structure of an
IPv4-compatible IPv6 address and a few acceptable formats for the address.
IPv4-Compatible IPv6 Address Format
96 bits
32 bits
0
IPv4 address
::192.168.30.1
= ::C0A8:1E01
52727
Figure 3
Unique Local Address
A unique local address is an IPv6 unicast address that is globally unique and is intended for local
communications. They are not expected to be routable on the global Internet and are routable inside of
a limited area, such as a site. They may also be routed between a limited set of sites.
A unique local address has the following characteristics:
•
It has a globally unique prefix (that is, it has a high probability of uniqueness).
•
It has a well-known prefix to allow for easy filtering at site boundaries.
•
It allows sites to be combined or privately interconnected without creating any address conflicts or
requiring renumbering of interfaces that use these prefixes.
•
It is ISP-independent and can be used for communications inside of a site without having any
permanent or intermittent Internet connectivity.
•
If it is accidentally leaked outside of a site via routing or DNS, there is no conflict with any other
addresses.
•
Applications may treat unique local addresses like global scoped addresses.
Figure 4 shows the structure of a unique local address.
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Implementing IPv6 Addressing and Basic Connectivity
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Figure 4
Unique Local Address Structure
/7
FC00
/48
/64
Interface ID
Global ID 41 bits
Local IPv6
Subnet prefix
Link prefix
• Prefix — FC00::/7 prefix to identify local IPv6 unicast addresses.
• Subnet ID — 16-bit subnet ID is an identifier of a subnet within the site.
• Interface ID — 64-bit IID
232389
• Global ID — 41-bit global identifier used to create a globally unique prefix.
Site-Local Address
Because RFC 3879 deprecates the use of site-local addresses, configuration of private IPv6 addresses
should be done following the recommendations of unique local addressing (ULA) in RFC 4193.
IPv6 Address Type: Anycast
An anycast address is an address that is assigned to a set of interfaces that typically belong to different
nodes. A packet sent to an anycast address is delivered to the closest interface—as defined by the routing
protocols in use—identified by the anycast address. Anycast addresses are syntactically
indistinguishable from unicast addresses because anycast addresses are allocated from the unicast
address space. Assigning a unicast address to more than one interface makes a unicast address an anycast
address. Nodes to which the anycast address is assigned must be explicitly configured to recognize that
the address is an anycast address.
Anycast addresses can be used only by a router, not a host, and anycast addresses must not be used as
the source address of an IPv6 packet.
Figure 5 shows the format of the subnet router anycast address; the address has a prefix concatenated by
a series of zeros (the interface ID). The subnet router anycast address can be used to reach a router on
the link that is identified by the prefix in the subnet router anycast address.
Figure 5
Subnet Router Anycast Address Format
128 bits
Prefix
0000000000000...000
52670
Note
The following shows the configuration for an anycast prefix for 6to4 relay routers:
interface Tunnel0
no ip address
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Implementing IPv6 Addressing and Basic Connectivity
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ipv6 address 2001:0DB8:A00:1::1/64
ipv6 address 2001:oDB8:c058:6301::/128 anycast
tunnel source Ethernet0
tunnel mode ipv6ip 6to4
!
interface Ethernet0
ip address 10.0.0.1 255.255.255.0
ip address 192.88.99.1 255.255.255.0 secondary
!
ipv6 route 2001:0DB8::/16 Tunnel0
!
IPv6 Address Type: Multicast
An IPv6 multicast address is an IPv6 address that has a prefix of FF00::/8 (1111 1111). An IPv6
multicast address is an identifier for a set of interfaces that typically belong to different nodes. A packet
sent to a multicast address is delivered to all interfaces identified by the multicast address. The second
octet following the prefix defines the lifetime and scope of the multicast address. A permanent multicast
address has a lifetime parameter equal to 0; a temporary multicast address has a lifetime parameter equal
to 1. A multicast address that has the scope of a node, link, site, or organization, or a global scope has a
scope parameter of 1, 2, 5, 8, or E, respectively. For example, a multicast address with the prefix
FF02::/16 is a permanent multicast address with a link scope. Figure 6 shows the format of the IPv6
multicast address.
Figure 6
IPv6 Multicast Address Format
128 bits
0
F
8 bits
F
4 bits
4 bits
Lifetime Scope
8 bits
Lifetime =
0 if permanent
1 if temporary
1 = node
2 = link
Scope = 5 = site
8 = organization
E = global
52671
1111 1111
Interface ID
IPv6 nodes (hosts and routers) are required to join (receive packets destined for) the following multicast
groups:
•
All-nodes multicast group FF02:0:0:0:0:0:0:1 (scope is link-local)
•
Solicited-node multicast group FF02:0:0:0:0:1:FF00:0000/104 for each of its assigned unicast and
anycast addresses
IPv6 routers must also join the all-routers multicast group FF02:0:0:0:0:0:0:2 (scope is link-local).
The solicited-node multicast address is a multicast group that corresponds to an IPv6 unicast or anycast
address. IPv6 nodes must join the associated solicited-node multicast group for every unicast and
anycast address to which it is assigned. The IPv6 solicited-node multicast address has the prefix
FF02:0:0:0:0:1:FF00:0000/104 concatenated with the 24 low-order bits of a corresponding IPv6 unicast
or anycast address (see Figure 7). For example, the solicited-node multicast address corresponding to the
IPv6 address 2037::01:800:200E:8C6C is FF02::1:FF0E:8C6C. Solicited-node addresses are used in
neighbor solicitation messages.
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Figure 7
IPv6 Solicited-Node Multicast Address Format
IPv6 unicast or anycast address
Prefix
Interface ID
24 bits
Solicited-node multicast address
FF02
0
1
FF
Lower 24
52672
128 bits
Note
There are no broadcast addresses in IPv6. IPv6 multicast addresses are used instead of broadcast
addresses.
For further information on IPv6 multicast, see the Implementing IPv6 Multicast document.
IPv6 Address Output Display
When IPv6 or IPv4 command output displays an IPv6 address, a long IPv6 address can overflow into
neighboring fields, causing the output to be difficult to read. The output fields were designed to work
with the longest possible IPv4 address, which has 15 characters; IPv6 addresses can be up to 39
characters long. The following scheme has been adopted in IPv4 and IPv6 commands to allow the
appropriate length of IPv6 address to be displayed and move the following fields to the next line, if
necessary. The fields that are moved are kept in alignment with the header row.
Using the output display from the where command as an example, eight connections are displayed. The
first six connections feature IPv6 addresses; the last two connections feature IPv4 addresses.
Router# where
Conn Host
1 test5
2 test4
3
4
5
6
7
8
Address
Byte Idle Conn Name
2001:0DB8:3333:4::5
6
24 test5
2001:0DB8:3333:44::5
6
24 test4
2001:0DB8:3333:4::5 2001:0DB8:3333:4::5
6
24 2001:0DB8:3333:4::5
2001:0DB8:3333:44::5
2001:0DB8:3333:44::5
6
23 2001:0DB8:3333:44::5
2001:0DB8:3000:4000:5000:6000:7000:8001
2001:0DB8:3000:4000:5000:6000:7000:8001
6
20 2001:0DB8:3000:4000:5000:6000:
2001:0DB8:1::1
2001:0DB8:1::1
0
1 2001:0DB8:1::1
10.1.9.1
10.1.9.1
0
0 10.1.9.1
10.222.111.222
10.222.111.222
0
0 10.222.111.222
Connection 1 contains an IPv6 address that uses the maximum address length in the address field.
Connection 2 shows the IPv6 address overflowing the address field and the following fields moved to
the next line, but in alignment with the appropriate headers. Connection 3 contains an IPv6 address that
fills the maximum length of the hostname and address fields without wrapping any lines. Connection 4
shows the effect of both the hostname and address fields containing a long IPv6 address. The output is
shown over three lines keeping the correct heading alignment. Connection 5 displays a similar effect as
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Implementing IPv6 Addressing and Basic Connectivity
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connection 4 with a very long IPv6 address in the hostname and address fields. Note that the connection
name field is actually truncated. Connection 6 displays a very short IPv6 address that does not require
any change in the display. Connections 7 and 8 display short and long IPv4 addresses.
Note
The IPv6 address output display applies to all commands that display IPv6 addresses.
Simplified IPv6 Packet Header
The basic IPv4 packet header has 12 fields with a total size of 20 octets (160 bits) (see Figure 8). The
12 fields may be followed by an Options field, which is followed by a data portion that is usually the
transport-layer packet. The variable length of the Options field adds to the total size of the IPv4 packet
header. The shaded fields of the IPv4 packet header shown in Figure 8 are not included in the IPv6 packet
header.
Figure 8
Version
IPv4 Packet Header Format
Hd Len
Type of Service
Identification
Time to Live
Total Length
Flags
Protocol
Fragment Offset
Header Checksum
Source Address
20
octets
Destination Address
Padding
Data Portion
32 bits
Variable
length
51457
Options
The basic IPv6 packet header has 8 fields with a total size of 40 octets (320 bits) (see Figure 9). Fields
were removed from the IPv6 header because, in IPv6, fragmentation is not handled by routers and
checksums at the network layer are not used. Instead, fragmentation in IPv6 is handled by the source of
a packet and checksums at the data link layer and transport layer are used. (In IPv4, the User Datagram
Protocol (UDP) transport layer uses an optional checksum. In IPv6, use of the UDP checksum is required
to check the integrity of the inner packet.) Additionally, the basic IPv6 packet header and Options field
are aligned to 64 bits, which can facilitate the processing of IPv6 packets.
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Figure 9
IPv6 Packet Header Format
Version
Traffic Class
Flow Label
Payload Length
Next Header
Hop Limit
Source Address
40
octets
Destination Address
Next Header
Extension Header information
Variable
length
32 bits
51458
Data Portion
Table 2 lists the fields in the basic IPv6 packet header.
Table 2
Basic IPv6 Packet Header Fields
Field
Description
Version
Similar to the Version field in the IPv4 packet header, except that the
field lists number 6 for IPv6 instead of number 4 for IPv4.
Traffic Class
Similar to the Type of Service field in the IPv4 packet header. The
Traffic Class field tags packets with a traffic class that is used in
differentiated services.
Flow Label
A new field in the IPv6 packet header. The Flow Label field tags packets
with a specific flow that differentiates the packets at the network layer.
Payload Length
Similar to the Total Length field in the IPv4 packet header. The Payload
Length field indicates the total length of the data portion of the packet.
Next Header
Similar to the Protocol field in the IPv4 packet header. The value of the
Next Header field determines the type of information following the
basic IPv6 header. The type of information following the basic IPv6
header can be a transport-layer packet, for example, a TCP or UDP
packet, or an Extension Header, as shown in Figure 9.
Hop Limit
Similar to the Time to Live field in the IPv4 packet header. The value of
the Hop Limit field specifies the maximum number of routers that an
IPv6 packet can pass through before the packet is considered invalid.
Each router decrements the value by one. Because no checksum is in the
IPv6 header, the router can decrement the value without needing to
recalculate the checksum, which saves processing resources.
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Table 2
Basic IPv6 Packet Header Fields (continued)
Field
Description
Source Address
Similar to the Source Address field in the IPv4 packet header, except
that the field contains a 128-bit source address for IPv6 instead of a
32-bit source address for IPv4.
Destination Address
Similar to the Destination Address field in the IPv4 packet header,
except that the field contains a 128-bit destination address for IPv6
instead of a 32-bit destination address for IPv4.
Following the eight fields of the basic IPv6 packet header are optional extension headers and the data
portion of the packet. If present, each extension header is aligned to 64 bits. There is no fixed number of
extension headers in an IPv6 packet. Together, the extension headers form a chain of headers. Each
extension header is identified by the Next Header field of the previous header. Typically, the final
extension header has a Next Header field of a transport-layer protocol, such as TCP or UDP. Figure 10
shows the IPv6 extension header format.
Figure 10
IPv6 Extension Header Format
IPv6 basic header
(40 octets)
IPv6
packet
Any number of
extension headers
Data (for example,
TCP or UDP)
Ext Header Length
Extension Header Data
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Table 3 lists the extension header types and their Next Header field values.
Table 3
IPv6 Extension Header Types
Header Type
Next
Header
Value
Hop-by-hop options header
0
This header is processed by all hops in the path of a packet.
When present, the hop-by-hop options header always
follows immediately after the basic IPv6 packet header.
Destination options header
60
The destination options header can follow any hop-by-hop
options header, in which case the destination options header
is processed at the final destination and also at each visited
address specified by a routing header. Alternatively, the
destination options header can follow any Encapsulating
Security Payload (ESP) header, in which case the destination
options header is processed only at the final destination.
Routing header
43
The routing header is used for source routing.
Fragment header
44
The fragment header is used when a source must fragment a
packet that is larger than the maximum transmission unit
(MTU) for the path between itself and a destination. The
Fragment header is used in each fragmented packet.
Authentication header
51
The Authentication header and the ESP header are used
within IP Security Protocol (IPsec) to provide
authentication, integrity, and confidentiality of a packet.
These headers are identical for both IPv4 and IPv6.
and
Description
ESP header
50
Upper-layer headers
6 (TCP)
The upper-layer (transport) headers are the typical headers
used inside a packet to transport the data. The two main
17 (UDP)
transport protocols are TCP and UDP.
Mobility headers
135
Extension headers used by mobile nodes, correspondent
nodes, and home agents in all messaging related to the
creation and management of bindings.
Cisco Express Forwarding and Distributed Cisco Express Forwarding
Switching for IPv6
Cisco Express Forwarding is advanced, Layer 3 IP switching technology for the forwarding of IPv6
packets. Distributed Cisco Express Forwarding performs the same functions as Cisco Express
Forwarding but for distributed architecture platforms such as the Cisco 12000 series Internet routers and
the Cisco 7500 series routers. Distributed Cisco Express Forwarding for IPv6 and Cisco Express
Forwarding for IPv6 function the same and offer the same benefits as for distributed Cisco Express
Forwarding for IPv4 and Cisco Express Forwarding for IPv4—network entries that are added, removed,
or modified in the IPv6 Routing Information Base (RIB), as dictated by the routing protocols in use, are
reflected in the Forwarding Information Bases (FIBs), and the IPv6 adjacency tables maintain Layer 2
next-hop addresses for all entries in each FIB.
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Note
By default, the Cisco 12000 series Internet routers support only distributed Cisco Express Forwarding
(Cisco Express Forwarding switching is performed by the line cards). The Cisco 7500 series routers
support both Cisco Express Forwarding and distributed Cisco Express Forwarding. When Cisco Express
Forwarding is configured on Cisco 7500 series routers, Cisco Express Forwarding switching is
performed by the Route Processor (RP); when distributed Cisco Express Forwarding is configured,
Cisco Express Forwarding switching is performed by the line cards.
In Cisco IOS Release 12.0(21)ST, distributed Cisco Express Forwarding included support for IPv6
addresses and prefixes. In Cisco IOS Release 12.0(22)S or later releases and Cisco IOS
Release 12.2(13)T or later releases, distributed Cisco Express Forwarding and Cisco Express
Forwarding were enhanced to include support for separate FIBs for IPv6 global and link-local addresses.
Each IPv6 router interface has an association to one IPv6 global FIB and one IPv6 link-local FIB
(multiple interfaces can have an association to the same FIB). All IPv6 router interfaces that are attached
to the same IPv6 link share the same IPv6 link-local FIB. IPv6 packets that have an IPv6 global
destination address are processed by the IPv6 global FIB; however, packets that have an IPv6 global
destination address and an IPv6 link-local source address are sent to the RP for process switching and
scope-error handling. Packets that have a link-local source address are not forwarded off of the local link
and are sent to the RP for process switching and scope-error handling.
Unicast Reverse Path Forwarding
Use the Unicast RPF feature to mitigate problems caused by malformed or forged (spoofed) IPv6 source
addresses that pass through an IPv6 router. Malformed or forged source addresses can indicate
denial-of-service (DoS) attacks based on source IPv6 address spoofing.
When Unicast RPF is enabled on an interface, the router examines all packets received on that interface.
The router verifies that the source address appears in the routing table and matches the interface on
which the packet was received. This “look backward” ability is available only when Cisco Express
Forwarding is enabled on the router, because the lookup relies on the presence of the FIB. Cisco Express
Forwarding generates the FIB as part of its operation.
Note
Unicast RPF is an input function and is applied only on the input interface of a router at the upstream
end of a connection.
The Unicast RPF feature verifies whether any packet received at a router interface arrives on one of the
best return paths to the source of the packet. The feature performs a reverse lookup in the Cisco Express
Forwarding table. If Unicast RPF does not find a reverse path for the packet, Unicast RPF can drop or
forward the packet, depending on whether an access control list (ACL) is specified. If an ACL is
specified, then when (and only when) a packet fails the Unicast RPF check, the ACL is checked to verify
if the packet should be dropped (using a deny statement in the ACL) or forwarded (using a permit
statement in the ACL). Whether a packet is dropped or forwarded, the packet is counted in the global IP
traffic statistics for Unicast RPF drops and in the interface statistics for Unicast RPF.
If no ACL is specified, the router drops the forged or malformed packet immediately and no ACL logging
occurs. The router and interface Unicast RPF counters are updated.
Unicast RPF events can be logged by specifying the logging option for the ACL entries. Log information
can be used to gather information about the attack, such as source address and time.
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Note
With Unicast RPF, all equal-cost “best” return paths are considered valid. Unicast RPF works in cases
where multiple return paths exist, provided that each path is equal to the others in terms of the routing
cost (number of hops, weights, and so on) and as long as the route is in the FIB.
DNS for IPv6
IPv6 supports DNS record types that are supported in the DNS name-to-address and address-to-name
lookup processes. The DNS record types support IPv6 addresses. IPv6 also supports the reverse mapping
of IPv6 addresses to DNS names.
Note
IP6.ARPA support was added in the Cisco IOS 12.3(11)T release. IP6.ARPA is not supported in releases
prior to the Cisco IOS 12.3(11)T release.
Table 4 lists the IPv6 DNS record types.
Table 4
IPv6 DNS Record Types
Record Type
Description
Format
AAAA
Maps a hostname to an IPv6 address. (Equivalent to an A
record in IPv4.)
www.abc.test AAAA 3FFE:YYYY:C18:1::2
Note
PTR
Support for AAAA records and A records over an
IPv6 transport or IPv4 transport is in Cisco IOS
Release 12.2(8)T or later releases.
Maps an IPv6 address to a hostname. (Equivalent to a PTR
record in IPv4.)
Note
2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.8.1.c.0.
y.y.y.y.e.f.f.3.ip6.int PTR www.abc.test
The Cisco IOS software supports resolution of PTR
records for the IP6.INT domain.
Path MTU Discovery for IPv6
As in IPv4, path MTU discovery in IPv6 allows a host to dynamically discover and adjust to differences
in the MTU size of every link along a given data path. In IPv6, however, fragmentation is handled by the
source of a packet when the path MTU of one link along a given data path is not large enough to
accommodate the size of the packets. Having IPv6 hosts handle packet fragmentation saves IPv6 router
processing resources and helps IPv6 networks run more efficiently.
Note
In IPv6, the minimum link MTU is 1280 octets. Cisco recommends using an MTU value of 1500 octets
for IPv6 links.
Cisco Discovery Protocol IPv6 Address Support
The Cisco Discovery Protocol IPv6 address support for neighbor information feature adds the ability to
transfer IPv6 addressing information between two Cisco devices. Cisco Discovery Protocol support for
IPv6 addresses provides IPv6 information to network management products and troubleshooting tools.
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ICMP for IPv6
Internet Control Message Protocol (ICMP) in IPv6 functions the same as ICMP in IPv4. ICMP generates
error messages, such as ICMP destination unreachable messages, and informational messages, such as
ICMP echo request and reply messages. Additionally, ICMP packets in IPv6 are used in the IPv6
neighbor discovery process, path MTU discovery, and the Multicast Listener Discovery (MLD) protocol
for IPv6. MLD is used by IPv6 routers to discover multicast listeners (nodes that want to receive
multicast packets destined for specific multicast addresses) on directly attached links. MLD is based on
version 2 of the Internet Group Management Protocol (IGMP) for IPv4.
A value of 58 in the Next Header field of the basic IPv6 packet header identifies an IPv6 ICMP packet.
ICMP packets in IPv6 are like a transport-layer packet in the sense that the ICMP packet follows all the
extension headers and is the last piece of information in the IPv6 packet. Within IPv6 ICMP packets, the
ICMPv6 Type and ICMPv6 Code fields identify IPv6 ICMP packet specifics, such as the ICMP message
type. The value in the Checksum field is derived (computed by the sender and checked by the receiver)
from the fields in the IPv6 ICMP packet and the IPv6 pseudoheader. The ICMPv6 Data field contains
error or diagnostic information relevant to IP packet processing. Figure 11 shows the IPv6 ICMP packet
header format.
Figure 11
IPv6 ICMP Packet Header Format
Next header = 58
ICMPv6 packet
IPv6 basic header
ICMPv6 packet
ICMPv6 Type
ICMPv6 Code
Checksum
52728
ICMPv6 Data
IPv6 Neighbor Discovery
The IPv6 neighbor discovery process uses ICMP messages and solicited-node multicast addresses to
determine the link-layer address of a neighbor on the same network (local link), verify the reachability
of a neighbor, and track neighboring routers.
The IPv6 static cache entry for neighbor discovery feature allows static entries to be made in the IPv6
neighbor cache. Static routing requires an administrator to manually enter IPv6 addresses, subnet masks,
gateways, and corresponding MAC addresses for each interface of each router into a table. Static routing
enables more control but requires more work to maintain the table. The table must be updated each time
routes are added or changed.
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Stateful Switchover
IPv6 neighbor discovery supports stateful switchover (SSO) using Cisco Express Forwarding. When
switchover occurs, the Cisco Express Forwarding adjacency state, which is checkpointed, is used to
reconstruct the neighbor discovery cache.
IPv6 Neighbor Solicitation Message
A value of 135 in the Type field of the ICMP packet header identifies a neighbor solicitation message.
Neighbor solicitation messages are sent on the local link when a node wants to determine the link-layer
address of another node on the same local link (see Figure 12). When a node wants to determine the
link-layer address of another node, the source address in a neighbor solicitation message is the IPv6
address of the node sending the neighbor solicitation message. The destination address in the neighbor
solicitation message is the solicited-node multicast address that corresponds to the IPv6 address of the
destination node. The neighbor solicitation message also includes the link-layer address of the source
node.
Figure 12
IPv6 Neighbor Discovery—Neighbor Solicitation Message
ICMPv6 Type = 135
Src = A
Dst = solicited-node multicast of B
Data = link-layer address of A
Query = what is your link address?
A and B can now exchange
packets on this link
52673
ICMPv6 Type = 136
Src = B
Dst = A
Data = link-layer address of B
After receiving the neighbor solicitation message, the destination node replies by sending a neighbor
advertisement message, which has a value of 136 in the Type field of the ICMP packet header, on the
local link. The source address in the neighbor advertisement message is the IPv6 address of the node
(more specifically, the IPv6 address of the node interface) sending the neighbor advertisement message.
The destination address in the neighbor advertisement message is the IPv6 address of the node that sent
the neighbor solicitation message. The data portion of the neighbor advertisement message includes the
link-layer address of the node sending the neighbor advertisement message.
After the source node receives the neighbor advertisement, the source node and destination node can
communicate.
Neighbor solicitation messages are also used to verify the reachability of a neighbor after the link-layer
address of a neighbor is identified. When a node wants to verifying the reachability of a neighbor, the
destination address in a neighbor solicitation message is the unicast address of the neighbor.
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Neighbor advertisement messages are also sent when there is a change in the link-layer address of a node
on a local link. When there is such a change, the destination address for the neighbor advertisement is
the all-nodes multicast address.
Neighbor solicitation messages are also used to verify the reachability of a neighbor after the link-layer
address of a neighbor is identified. Neighbor unreachability detection identifies the failure of a neighbor
or the failure of the forward path to the neighbor, and is used for all paths between hosts and neighboring
nodes (hosts or routers). Neighbor unreachability detection is performed for neighbors to which only
unicast packets are being sent and is not performed for neighbors to which multicast packets are being
sent.
A neighbor is considered reachable when a positive acknowledgment is returned from the neighbor
(indicating that packets previously sent to the neighbor have been received and processed). A positive
acknowledgment—from an upper-layer protocol (such as TCP)—indicates that a connection is making
forward progress (reaching its destination) or the receipt of a neighbor advertisement message in
response to a neighbor solicitation message. If packets are reaching the peer, they are also reaching the
next-hop neighbor of the source. Therefore, forward progress is also a confirmation that the next-hop
neighbor is reachable.
For destinations that are not on the local link, forward progress implies that the first-hop router is
reachable. When acknowledgments from an upper-layer protocol are not available, a node probes the
neighbor using unicast neighbor solicitation messages to verify that the forward path is still working.
The return of a solicited neighbor advertisement message from the neighbor is a positive
acknowledgment that the forward path is still working (neighbor advertisement messages that have the
solicited flag set to a value of 1 are sent only in response to a neighbor solicitation message). Unsolicited
messages confirm only the one-way path from the source to the destination node; solicited neighbor
advertisement messages indicate that a path is working in both directions.
Note
A neighbor advertisement message that has the solicited flag set to a value of 0 must not be considered
as a positive acknowledgment that the forward path is still working.
Neighbor solicitation messages are also used in the stateless autoconfiguration process to verify the
uniqueness of unicast IPv6 addresses before the addresses are assigned to an interface. Duplicate address
detection is performed first on a new, link-local IPv6 address before the address is assigned to an
interface (the new address remains in a tentative state while duplicate address detection is performed).
Specifically, a node sends a neighbor solicitation message with an unspecified source address and a
tentative link-local address in the body of the message. If another node is already using that address, the
node returns a neighbor advertisement message that contains the tentative link-local address. If another
node is simultaneously verifying the uniqueness of the same address, that node also returns a neighbor
solicitation message. If no neighbor advertisement messages are received in response to the neighbor
solicitation message and no neighbor solicitation messages are received from other nodes that are
attempting to verify the same tentative address, the node that sent the original neighbor solicitation
message considers the tentative link-local address to be unique and assigns the address to the interface.
Every IPv6 unicast address (global or link-local) must be verified for uniqueness on the link; however,
until the uniqueness of the link-local address is verified, duplicate address detection is not performed on
any other IPv6 addresses associated with the link-local address. The Cisco implementation of duplicate
address detection in the Cisco IOS software does not verify the uniqueness of anycast or global addresses
that are generated from 64-bit interface identifiers.
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IPv6 Router Advertisement Message
Router advertisement (RA) messages, which have a value of 134 in the Type field of the ICMP packet
header, are periodically sent out each configured interface of an IPv6 router. For stateless
autoconfiguration to work properly, the advertised prefix length in RA messages must always be 64 bits.
The RA messages are sent to the all-nodes multicast address (see Figure 13).
IPv6 Neighbor Discovery—RA Message
Router
advertisement
Router
advertisement
Router advertisement packet definitions:
ICMPv6 Type = 134
Src = router link-local address
Dst = all-nodes multicast address
Data = options, prefix, lifetime, autoconfig flag
52674
Figure 13
RA messages typically include the following information:
•
One or more onlink IPv6 prefixes that nodes on the local link can use to automatically configure
their IPv6 addresses
•
Lifetime information for each prefix included in the advertisement
•
Sets of flags that indicate the type of autoconfiguration (stateless or stateful) that can be completed
•
Default router information (whether the router sending the advertisement should be used as a default
router and, if so, the amount of time (in seconds) the router should be used as a default router)
•
Additional information for hosts, such as the hop limit and MTU a host should use in packets that it
originates
RAs are also sent in response to router solicitation messages. Router solicitation messages, which have
a value of 133 in the Type field of the ICMP packet header, are sent by hosts at system startup so that
the host can immediately autoconfigure without needing to wait for the next scheduled RA message.
Given that router solicitation messages are usually sent by hosts at system startup (the host does not have
a configured unicast address), the source address in router solicitation messages is usually the
unspecified IPv6 address (0:0:0:0:0:0:0:0). If the host has a configured unicast address, the unicast
address of the interface sending the router solicitation message is used as the source address in the
message. The destination address in router solicitation messages is the all-routers multicast address with
a scope of the link. When an RA is sent in response to a router solicitation, the destination address in the
RA message is the unicast address of the source of the router solicitation message.
The following RA message parameters can be configured:
•
The time interval between periodic RA messages
•
The “router lifetime” value, which indicates the usefulness of a router as the default router (for use
by all nodes on a given link)
•
The network prefixes in use on a given link
•
The time interval between neighbor solicitation message retransmissions (on a given link)
•
The amount of time a node considers a neighbor reachable (for use by all nodes on a given link)
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The configured parameters are specific to an interface. The sending of RA messages (with default
values) is automatically enabled on Ethernet and FDDI interfaces when the ipv6 unicast-routing
command is configured. For other interface types, the sending of RA messages must be manually
configured by using the no ipv6 nd ra suppress command. The sending of RA messages can be disabled
on individual interfaces by using the ipv6 nd ra suppress command.
Default Router Preferences for Traffic Engineering
Hosts discover and select default routers by listening to RAs. Typical default router selection
mechanisms are suboptimal in certain cases, such as when traffic engineering is needed. For example,
two routers on a link may provide equivalent but not equal-cost routing, and policy may dictate that one
of the routers is preferred. Some examples are as follows:
•
Multiple routers that route to distinct sets of prefixes—Redirects (sent by nonoptimal routers for a
destination) mean that hosts can choose any router and the system will work. However, traffic
patterns may mean that choosing one of the routers would lead to considerably fewer redirects.
•
Accidentally deploying a new router—Deploying a new router before it has been fully configured
could lead to hosts adopting the new router as a default router and traffic disappearing. Network
managers may want to indicate that some routers are more preferred than others.
•
Multihomed situations—Multihomed situations may become more common, because of multiple
physical links and because of the use of tunneling for IPv6 transport. Some of the routers may not
provide full default routing because they route only to the 6-to-4 prefix or they route only to a
corporate intranet. These situations cannot be resolved with redirects, which operate only over a
single link.
The default router preference (DRP) extension provides a coarse preference metric (low, medium, or
high) for default routers. The DRP of a default router is signaled in unused bits in RA messages. This
extension is backward compatible, both for routers (setting the DRP bits) and hosts (interpreting the
DRP bits). These bits are ignored by hosts that do not implement the DRP extension. Similarly, the
values sent by routers that do not implement the DRP extension will be interpreted by hosts that do
implement it as indicating a “medium” preference.
DRPs need to be configured manually. For information on configuring the optional DRP extension, see
the “Configuring the DRP Extension for Traffic Engineering” section.
IPv6 Neighbor Redirect Message
A value of 137 in the type field of the ICMP packet header identifies an IPv6 neighbor redirect message.
Routers send neighbor redirect messages to inform hosts of better first-hop nodes on the path to a
destination (see Figure 14).
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Implementing IPv6 Addressing and Basic Connectivity
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Figure 14
Router B
IPv6 Neighbor Discovery—Neighbor Redirect Message
Host H
Router A
IPv6 packet
Neighbor redirect packet definitions:
ICMPv6 Type = 137
Src = link-local address of Router A
Dst = link-local address of Host H
Data = target address (link-local
address of Router B), options
(header of redirected packet)
60981
Note: If the target is a host, the target
address is equal to the destination
address of the redirect packet and
the options include the link-layer
address of the target host (if known).
Subsequent IPv6 packets
Note
A router must be able to determine the link-local address for each of its neighboring routers in order to
ensure that the target address (the final destination) in a redirect message identifies the neighbor router
by its link-local address. For static routing, the address of the next-hop router should be specified using
the link-local address of the router; for dynamic routing, all IPv6 routing protocols must exchange the
link-local addresses of neighboring routers.
After forwarding a packet, a router should send a redirect message to the source of the packet under the
following circumstances:
•
The destination address of the packet is not a multicast address.
•
The packet was not addressed to the router.
•
The packet is about to be sent out the interface on which it was received.
•
The router determines that a better first-hop node for the packet resides on the same link as the
source of the packet.
•
The source address of the packet is a global IPv6 address of a neighbor on the same link, or a
link-local address.
Use the ipv6 icmp error-interval command to limit the rate at which the router generates all IPv6 ICMP
error messages, including neighbor redirect messages, which ultimately reduces link-layer congestion.
Note
A router must not update its routing tables after receiving a neighbor redirect message, and hosts must
not originate neighbor redirect messages.
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Link, Subnet, and Site Addressing Changes
This section describes the IPv6 stateless autoconfiguration and general prefix features, which can be
used to manage link, subnet, and site addressing changes.
IPv6 Stateless Autoconfiguration
All interfaces on IPv6 nodes must have a link-local address, which is usually automatically configured
from the identifier for an interface and the link-local prefix FE80::/10. A link-local address enables a
node to communicate with other nodes on the link and can be used to further configure the node.
Nodes can connect to a network and automatically generate global IPv6 addresses without the need for
manual configuration or help of a server, such as a Dynamic Host Configuration Protocol (DHCP) server.
With IPv6, a router on the link advertises in RA messages any global prefixes, and its willingness to
function as a default router for the link. RA messages are sent periodically and in response to router
solicitation messages, which are sent by hosts at system startup.
A node on the link can automatically configure global IPv6 addresses by appending its interface
identifier (64 bits) to the prefixes (64 bits) included in the RA messages. The resulting 128-bit IPv6
addresses configured by the node are then subjected to duplicate address detection to ensure their
uniqueness on the link. If the prefixes advertised in the RA messages are globally unique, then the IPv6
addresses configured by the node are also guaranteed to be globally unique. Router solicitation
messages, which have a value of 133 in the Type field of the ICMP packet header, are sent by hosts at
system startup so that the host can immediately autoconfigure without needing to wait for the next
scheduled RA message.
Simplified Network Renumbering for IPv6 Hosts
The strict aggregation of the global routing table requires that networks be renumbered when the service
provider for the network is changed. When the stateless autoconfiguration functionality in IPv6 is used
to renumber a network, the prefix from a new service provider is added to RA messages that are sent on
the link. (The RA messages contain both the prefix from the old service provider and the prefix from the
new service provider.) Nodes on the link automatically configure additional addresses by using the prefix
from the new service provider. The nodes can then use the addresses created from the new prefix and the
existing addresses created from the old prefix on the link. Configuration of the lifetime parameters
associated with the old and new prefixes means that nodes on the link can make the transition to using
only addresses created from the new prefix. During a transition period, the old prefix is removed from
RA messages and only addresses that contain the new prefix are used on the link (the renumbering is
complete) (see Figure 15).
Figure 15
IPv6 Network Renumbering for Hosts Using Stateless Autoconfiguration
Host autoconfigured
addresses are:
new address autoconfigured
from a new prefix and
old addresses autoconfigured
from an old prefix
24
Sends new network-type
information
(prefixes, [old and new] )
52677
MAC address:
00:2c:04:00:FF:56
Implementing IPv6 Addressing and Basic Connectivity
Information About Implementing IPv6 Addressing and Basic Connectivity
IPv6 General Prefixes
The upper 64 bits of an IPv6 address are composed from a global routing prefix plus a subnet ID, as
defined in RFC 3513. A general prefix (for example, /48) holds a short prefix, based on which a number
of longer, more specific prefixes (for example, /64) can be defined. When the general prefix is changed,
all of the more specific prefixes based on it will change, too. This function greatly simplifies network
renumbering and allows for automated prefix definition.
For example, a general prefix might be 48 bits long (“/48”) and the more specific prefixes generated from
it might be 64 bits long (“/64”). In the following example, the leftmost 48 bits of all the specific prefixes
will be the same—and the same as the general prefix itself. The next 16 bits are all different.
•
General prefix: 2001:0DB8:2222::/48
•
Specific prefix: 2001:0DB8:2222:0000::/64
•
Specific prefix: 2001:0DB8:2222:0001::/64
•
Specific prefix: 2001:0DB8:2222:4321::/64
•
Specific prefix: 2001:0DB8:2222:7744::/64
General prefixes can be defined in several ways:
•
Manually
•
Based on a 6to4 interface
•
Dynamically, from a prefix received by a DHCP for IPv6 prefix delegation client
More specific prefixes, based on a general prefix, can be used when configuring IPv6 on an interface.
DHCP for IPv6 Prefix Delegation
DHCP for IPv6 can be used in environments to deliver stateful and stateless information. For further
information about this feature, see Implementing DHCP for IPv6.
IPv6 Prefix Aggregation
The aggregatable nature of the IPv6 address space enables an IPv6 addressing hierarchy. For example,
an enterprise can subdivide a single IPv6 prefix from a service provider into multiple, longer prefixes
for use within its internal network. Conversely, a service provider can aggregate all of the prefixes of its
customers into a single, shorter prefix that the service provider can then advertise over the IPv6 internet
(see Figure 16).
IPv6 Prefix Aggregation
Customer
no. 1
2001:0410:0001::/48
Customer
no. 2
2001:0410:0002::/48
Only announces
the /35 prefix
ISP
2001:0410::/35
IPv6 Internet
2001::/16
52680
Figure 16
25
Implementing IPv6 Addressing and Basic Connectivity
Information About Implementing IPv6 Addressing and Basic Connectivity
IPv6 Site Multihoming
Multiple IPv6 prefixes can be assigned to networks and hosts. Having multiple prefixes assigned to a
network makes it easy for that network to connect to multiple ISPs without breaking the global routing
table (see Figure 17).
Figure 17
IPv6 Site Multihoming
ISP
2001:0410::/32
Announces the
2001:0410::/32 prefix
IPv6 Internet
2001::/16
Customer
no. 1
ISP
2001:0418::/32
Announces the
2001:0418::/32 prefix
52681
2001:0410:0001::/48
2001:0418:0001::/48
IPv6 Data Links
In IPv6 networks, a data link is a network sharing a particular link-local prefix. Data links are networks
arbitrarily segmented by a network administrator in order to provide a multilevel, hierarchical routing
structure while shielding the subnetwork from the addressing complexity of attached networks. The
function of a subnetwork in IPv6 is similar to a subnetwork in IPv4. A subnetwork prefix is associated
with one data link; multiple subnetwork prefixes may be assigned to the same data link.
The following data links are supported for IPv6: ATM permanent virtual circuit (PVC) and ATM LANE,
Ethernet, Fast Ethernet, Gigabit Ethernet, FDDI, Frame Relay PVC, Cisco High-Level Data Link
Control (HDLC), PPP over Packet over SONET, ISDN, serial interfaces, and dynamic packet transport
(DPT). See Start Here: Cisco IOS Software Release Specifics for IPv6 Features for release details on
supported data links.
Routed Bridge Encapsulation for IPv6
Routed bridge encapsulation (RBE) provides a mechanism for routing a protocol from a bridged
interface to another routed or bridged interface. RBE for IPv6 can be used on ATM point-to-point
subinterfaces that are configured for IPv6 half-bridging. Routing of IP packets and IPv6 half-bridging,
bridging, PPP over Ethernet (PPPoE), or other Ethernet 802.3-encapsulated protocols can be configured
on the same subinterface.
Dual IPv4 and IPv6 Protocol Stacks
The dual IPv4 and IPv6 protocol stack technique can be used to transition to IPv6. It enables gradual,
one-by-one upgrades to applications running on nodes. Applications running on nodes are upgraded to
make use of the IPv6 protocol stack. Applications that are not upgraded—they support only the IPv4
protocol stack—can coexist with upgraded applications on a node. New and upgraded applications make
use of both the IPv4 and IPv6 protocol stacks (see Figure 18).
26
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
Dual IPv4 and IPv6 Protocol Stack Technique
Existing Application
Upgraded Application
TCP
UDP
TCP
UDP
IPv4
IPv6
IPv4
IPv6
0x0800
0x86dd
Data Link (Ethernet)
0x0800
0x86dd
Frame
protocol ID
52683
Figure 18
Data Link (Ethernet)
One application program interface (API) supports both IPv4 and IPv6 addresses and DNS requests. An
application can be upgraded to the new API and still use only the IPv4 protocol stack. The Cisco IOS
software supports the dual IPv4 and IPv6 protocol stack technique. When an interface is configured with
both an IPv4 and an IPv6 address, the interface will forward both IPv4 and IPv6 traffic.
In Figure 19, an application that supports dual IPv4 and IPv6 protocol stacks requests all available
addresses for the destination hostname www.a.com from a DNS server. The DNS server replies with all
available addresses (both IPv4 and IPv6 addresses) for www.example.com. The application chooses an
address—in most cases, IPv6 addresses are the default choice—and connects the source node to the
destination using the IPv6 protocol stack.
Dual IPv4 and IPv6 Protocol Stack Applications
www.example.com
=*?
IPv4
3ffe:yyyy::1
10.1.1.1
DNS
server
10.1.1.1
52684
Figure 19
IPv6
3ffe:yyyy::1
How to Implement IPv6 Addressing and Basic Connectivity
The tasks in the following sections explain how to implement IPv6 addressing and basic connectivity:
•
Configuring IPv6 Addressing and Enabling IPv6 Routing, page 28
•
Defining and Using IPv6 General Prefixes, page 30
•
Configuring an Interface to Support the IPv4 and IPv6 Protocol Stacks, page 33
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Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
•
Configuring IPv6 ICMP Rate Limiting, page 34
•
Configuring the DRP Extension for Traffic Engineering, page 35
•
Configuring Cisco Express Forwarding and Distributed Cisco Express Forwarding Switching for
IPv6, page 36
•
Mapping Hostnames to IPv6 Addresses, page 41
•
Mapping IPv6 Addresses to IPv6 ATM and Frame Relay Interfaces, page 42
•
Displaying IPv6 Redirect Messages, page 45
Configuring IPv6 Addressing and Enabling IPv6 Routing
This task explains how to assign IPv6 addresses to individual router interfaces and enable the forwarding
of IPv6 traffic globally on the router. By default, IPv6 addresses are not configured and IPv6 routing is
disabled.
Note
The ipv6-address argument in the ipv6 address command must be in the form documented in RFC 2373
where the address is specified in hexadecimal using 16-bit values between colons.
The ipv6-prefix argument in the ipv6 address command must be in the form documented in RFC 2373
where the address is specified in hexadecimal using 16-bit values between colons.
The /prefix-length keyword and argument in the ipv6 address command is a decimal value that indicates
how many of the high-order contiguous bits of the address comprise the prefix (the network portion of
the address) A slash mark must precede the decimal value.
IPv6 Multicast Groups
An IPv6 address must be configured on an interface for the interface to forward IPv6 traffic. Configuring
a global IPv6 address on an interface automatically configures a link-local address and activates IPv6
for that interface. Additionally, the configured interface automatically joins the following required
multicast groups for that link:
•
Solicited-node multicast group FF02:0:0:0:0:1:FF00::/104 for each unicast and anycast address
assigned to the interface
•
All-nodes link-local multicast group FF02::1
•
All-routers link-local multicast group FF02::2
Note
The solicited-node multicast address is used in the neighbor discovery process.
Restrictions
In Cisco IOS Release 12.2(4)T or later releases, Cisco IOS Release 12.0(21)ST, and Cisco IOS
Release 12.0(22)S or later releases, the ipv6 address or ipv6 address eui-64 command can be used to
configure multiple IPv6 global addresses within the same prefix on an interface. Multiple IPv6 link-local
addresses on an interface are not supported.
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How to Implement IPv6 Addressing and Basic Connectivity
Prior to Cisco IOS Releases 12.2(4)T, 12.0(21)ST, and 12.0(22)S, the Cisco IOS command-line interface
(CLI) displays the following error message when multiple IPv6 addresses within the same prefix on an
interface are configured:
Prefix <prefix-number> already assigned to <interface-type>
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface type number
4.
ipv6 address ipv6-prefix/prefix-length eui-64
or
ipv6 address ipv6-address/prefix-length link-local
or
ipv6 address ipv6-prefix/prefix-length anycast
or
ipv6 enable
5.
exit
6.
ipv6 unicast-routing
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Specifies an interface type and number, and places the
router in interface configuration mode.
Example:
Router(config)# interface ethernet 0/0
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Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
Step 4
Command or Action
Purpose
ipv6 address ipv6-prefix/prefix-length eui-64
or
Specifies an IPv6 network assigned to the interface and
enables IPv6 processing on the interface.
ipv6 address ipv6-address/prefix-length
link-local
or
or
Specifies an IPv6 address assigned to the interface and
enables IPv6 processing on the interface.
ipv6 address ipv6-prefix/prefix-length anycast
or
or
Automatically configures an IPv6 link-local address on the
interface while also enabling the interface for IPv6
processing. The link-local address can be used only to
communicate with nodes on the same link.
ipv6 enable
Example:
Router(config-if)# ipv6 address
2001:0DB8:0:1::/64 eui-64
•
Specifying the ipv6 address eui-64 command
configures global IPv6 addresses with an interface
identifier (ID) in the low-order 64 bits of the IPv6
address. Only the 64-bit network prefix for the address
needs to be specified; the last 64 bits are automatically
computed from the interface ID.
•
Specifying the ipv6 address link-local command
configures a link-local address on the interface that is
used instead of the link-local address that is
automatically configured when IPv6 is enabled on the
interface.
•
Specifying the ipv6 address anycast command adds an
IPv6 anycast address.
or
Example:
Router(config-if)# ipv6 address
FE80::260:3EFF:FE11:6770 link-local
or
Example:
Router(config-if) ipv6 address
2001:0DB8:1:1:FFFF:FFFF:FFFF:FFFE/64 anycast
or
Example:
Router(config-if)# ipv6 enable
Step 5
Exits interface configuration mode, and returns the router to
global configuration mode.
exit
Example:
Router(config-if)# exit
Step 6
ipv6 unicast-routing
Enables the forwarding of IPv6 unicast datagrams.
Example:
Router(config)# ipv6 unicast-routing
Defining and Using IPv6 General Prefixes
General prefixes can be defined in several ways:
•
Manually
•
Based on a 6to4 interface
•
Dynamically, from a prefix received by a DHCP for IPv6 prefix delegation client
More specific prefixes, based on a general prefix, can be used when configuring IPv6 on an interface.
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Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
The following tasks describe how to define and use IPv6 general prefixes:
•
Defining a General Prefix Manually, page 31
•
Defining a General Prefix Based on a 6to4 Interface, page 31
•
Defining a General Prefix with the DHCP for IPv6 Prefix Delegation Client Function, page 32
•
Using a General Prefix in IPv6, page 32
Defining a General Prefix Manually
The following task describes how to define a general prefix manually.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ipv6 general-prefix prefix-name [ipv6-prefix/prefix-length] [6to4 interface-type interface-number]
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ipv6 general-prefix prefix-name
{ipv6-prefix/prefix-length | 6to4
interface-type interface-number}
Defines a general prefix for an IPv6 address.
When defining a general prefix manually, specify both the
ipv6-prefix and /prefix-length arguments.
Example:
Router(config)# ipv6 general-prefix my-prefix
2001:0DB8:2222::/48
Defining a General Prefix Based on a 6to4 Interface
The following task describes how to define a general prefix based on a 6to4 interface.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ipv6 general-prefix prefix-name [ipv6-prefix/prefix-length] [6to4 interface-type interface-number]
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Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ipv6 general-prefix prefix-name
{ipv6-prefix/prefix-length | 6to4
interface-type interface-number}
Example:
Router(config)# ipv6 general-prefix my-prefix
6to4 ethernet 0
Defines a general prefix for an IPv6 address.
When defining a general prefix based on a 6to4 interface,
specify the 6to4 keyword and the interface-type
interface-number arguments.
When defining a general prefix based on an interface used
for 6to4 tunneling, the general prefix will be of the form
2001:a.b.c.d::/48, where “a.b.c.d” is the IPv4 address of the
interface referenced.
Defining a General Prefix with the DHCP for IPv6 Prefix Delegation Client Function
You can define a general prefix dynamically using the DHCP for IPv6 prefix delegation client function.
For information on how to perform this task, see the Implementing DHCP for IPv6 module.
Using a General Prefix in IPv6
The following task describes how to use a general prefix in IPv6.
SUMMARY STEPS
32
1.
enable
2.
configure terminal
3.
interface type number
4.
ipv6 address {ipv6-address/prefix-length | prefix-name sub-bits/prefix-length}
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Specifies an interface type and number, and places the
router in interface configuration mode.
Example:
Router(config)# interface ethernet 0/0
Step 4
ipv6 address {ipv6-address/prefix-length |
prefix-name sub-bits/prefix-length}
Configures an IPv6 prefix name for an IPv6 address and
enables IPv6 processing on the interface.
Example:
Router(config-if) ipv6 address my-prefix
2001:0DB8:0:7272::/64
Configuring an Interface to Support the IPv4 and IPv6 Protocol Stacks
When an interface in a Cisco networking device is configured with both an IPv4 and an IPv6 address,
the interface forwards both IPv4 and IPv6 traffic—the interface can send and receive data on both IPv4
and IPv6 networks. To configure an interface in a Cisco networking device to support both the IPv4 and
IPv6 protocol stacks, perform the following task.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ipv6 unicast-routing
4.
interface type number
5.
ip address ip-address mask [secondary]
6.
ipv6 address {ipv6-address/prefix-length | prefix-name sub-bits/prefix-length}
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Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
DETAILED STEPS
Step 1
Command
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ipv6 unicast-routing
Enables the forwarding of IPv6 unicast datagrams.
Example:
Router(config)# ipv6 unicast routing
Step 4
interface type number
Specifies the interface type and number, and enters interface
configuration mode.
Example:
Router(config)# interface ethernet 0
Step 5
ip address ip-address mask [secondary
[vrf vrf-name]]
Specifies a primary or secondary IPv4 address for an interface.
Example:
Router(config-if)# ip address
192.168.99.1 255.255.255.0
Step 6
ipv6 address {ipv6-address/prefix-length
| prefix-name sub-bits/prefix-length}
Specifies the IPv6 network assigned to the interface and enables
IPv6 processing on the interface.
Note
Example:
Router(config-if)# ipv6 address
2001:0DB8:c18:1::3/64
See the “Configuring IPv6 Addressing and Enabling IPv6
Routing” section for more information on configuring IPv6
addresses.
Configuring IPv6 ICMP Rate Limiting
This task explains how to customize IPv6 ICMP rate limiting.
IPv6 ICMP Rate Limiting
In Cisco IOS Release 12.2(8)T or later releases, the IPv6 ICMP rate limiting feature implements a token
bucket algorithm for limiting the rate at which IPv6 ICMP error messages are sent out on the network.
The initial implementation of IPv6 ICMP rate limiting defined a fixed interval between error messages,
but some applications, such as traceroute, often require replies to a group of requests sent in rapid
succession. The fixed interval between error messages is not flexible enough to work with applications
such as traceroute and can cause the application to fail. Implementing a token bucket scheme allows a
number of tokens—representing the ability to send one error message each—to be stored in a virtual
bucket. The maximum number of tokens allowed in the bucket can be specified, and for every error
message to be sent, one token is removed from the bucket. If a series of error messages is generated,
34
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
error messages can be sent until the bucket is empty. When the bucket is empty of tokens, IPv6 ICMP
error messages are not sent until a new token is placed in the bucket. The token bucket algorithm does
not increase the average rate limiting time interval, and it is more flexible than the fixed time interval
scheme.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ipv6 icmp error-interval milliseconds [bucketsize]
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
ipv6 icmp error-interval milliseconds
[bucketsize]
Configures the interval and bucket size for IPv6 ICMP error
messages.
•
The milliseconds argument specifies the interval
between tokens being added to the bucket.
•
The optional bucketsize argument defines the maximum
number of tokens stored in the bucket.
Example:
Router(config)# ipv6 icmp error-interval 50 20
Configuring the DRP Extension for Traffic Engineering
This task describes how to configure the DRP extension to RAs in order to signal the preference value
of a default router.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface type number
4.
ipv6 nd router-preference {high | medium | low}
35
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Specifies the interface type and number, and enters interface
configuration mode.
Example:
Router(config)# interface ethernet 0
Step 4
ipv6 nd router-preference {high | medium | low}
Configures a DRP for a router on a specific interface
Example:
Router(config-if)# ipv6 nd router-preference high
Configuring Cisco Express Forwarding and Distributed Cisco Express
Forwarding Switching for IPv6
The following tasks explain how to configure Cisco Express Forwarding and distributed Cisco Express
Forwarding switching for IPv6:
•
Configuring Cisco Express Forwarding Switching on Distributed and Nondistributed Architecture
Platforms, page 36
•
Configuring Unicast RPF, page 39
Configuring Cisco Express Forwarding Switching on Distributed and Nondistributed Architecture
Platforms
Cisco Express Forwarding is designed for nondistributed architecture platforms, such as the Cisco 7200
series routers. Distributed Cisco Express Forwarding is designed for distributed architecture platforms,
such as the Cisco 12000 series Internet routers or the Cisco 7500 series routers. Nondistributed platforms
do not support distributed Cisco Express Forwarding; however, some distributed platforms, such as the
Cisco 7500 series routers, support both Cisco Express Forwarding and distributed Cisco Express
Forwarding.
When Cisco Express Forwarding is configured on Cisco 7500 series routers, Cisco Express Forwarding
switching is performed by the RP; when distributed Cisco Express Forwarding is configured,
Cisco Express Forwarding switching is performed by the line cards. By default, the Cisco 12000 series
Internet routers support only distributed Cisco Express Forwarding (Cisco Express Forwarding
switching is performed by the line cards).
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Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
Prerequisites
To enable the router to forward Cisco Express Forwarding and distributed Cisco Express Forwarding
traffic, use the ipv6 unicast-routing command to configure the forwarding of IPv6 unicast datagrams
globally on the router, and use the ipv6 address command to configure IPv6 address and IPv6 processing
on an interface.
You must enable Cisco Express Forwarding for IPv4 globally on the router by using the ip cef command
before enabling Cisco Express Forwarding for IPv6 globally on the router.
You must enable distributed Cisco Express Forwarding for IPv4 by using the ip cef distributed
command before enabling distributed Cisco Express Forwarding for IPv6.
Restrictions
The ipv6 cef and ipv6 cef distributed commands are not supported on the Cisco 12000 series Internet
routers because this distributed platform operates only in distributed Cisco Express Forwarding mode.
In Cisco IOS Release 12.0(22)S or later releases, the following restrictions apply to nondistributed and
distributed architecture platforms configured for Cisco Express Forwarding and distributed
Cisco Express Forwarding:
Note
By default, the Cisco 12000 series Internet routers support only distributed Cisco Express
Forwarding (Cisco Express Forwarding switching is performed by the line cards).
•
IPv6 packets that have global source and destination addresses are Cisco Express
Forwarding-switched or distributed Cisco Express Forwarding-switched.
•
IPv6 packets that have link-local source and destination addresses are process-switched.
•
IPv6 packets that are tunneled within manually configured IPv6 tunnels are Cisco Express
Forwarding-switched.
•
Only the following interface and encapsulation types are supported:
– ATM PVC and ATM LANE
– Cisco HDLC
– Ethernet, Fast Ethernet, and Gigabit Ethernet
– FDDI
– Frame Relay PVC
– PPP over Packet over SONET, ISDN, and serial (synchronous and asynchronous) interface
types
•
The following interface and encapsulation types are not supported:
– HP 100VG-AnyLAN
– Switched Multimegabit Data Service (SMDS)
– Token Ring
– X.25
Note
Contact your local Cisco Systems account representative for specific Cisco Express
Forwarding and distributed Cisco Express Forwarding hardware restrictions.
37
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ipv6 cef
or
ipv6 cef distributed
4.
ipv6 cef accounting [non-recursive | per-prefix | prefix-length]
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Example:
Router# configure terminal
38
Enters global configuration mode.
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
Step 3
Command or Action
Purpose
ipv6 cef
Enables Cisco Express Forwarding globally on the router.
or
or
ipv6 cef distributed
Enables distributed Cisco Express Forwarding globally on
the router.
Example:
Router(config)# ipv6 cef
or
Example:
Router(config)# ipv6 cef distributed
Step 4
ipv6 cef accounting [non-recursive | per-prefix
| prefix-length]
Example:
Enables Cisco Express Forwarding and distributed
Cisco Express Forwarding network accounting globally on
the router.
•
Network accounting for Cisco Express Forwarding and
distributed Cisco Express Forwarding enables you to
better understand Cisco Express Forwarding traffic
patterns within your network by collecting statistics
specific to Cisco Express Forwarding and distributed
Cisco Express Forwarding traffic. For example,
network accounting for Cisco Express Forwarding and
distributed Cisco Express Forwarding enables you to
collect information such as the number of packets and
bytes switched to a destination or the number of packets
switched through a destination.
•
The optional per-prefix keyword enables the collection
of the number of packets and bytes express forwarded
to an IPv6 destination (or IPv6 prefix).
•
The optional prefix-length keyword enables the
collection of the number of packets and bytes express
forwarded to an IPv6 prefix length.
Router(config)# ipv6 cef accounting
Note
When Cisco Express Forwarding is enabled
globally on the router, accounting information is
collected at the RP; when distributed Cisco Express
Forwarding is enabled globally on the router,
accounting information is collected at the line cards.
Configuring Unicast RPF
This task explains how to configure unicast RPF.
Prerequisites
To use Unicast RPF, enable Cisco Express Forwarding switching or distributed Cisco Express
Forwarding switching in the router. There is no need to configure the input interface for Cisco Express
Forwarding switching. As long as Cisco Express Forwarding is running on the router, individual
interfaces can be configured with other switching modes.
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Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
It is very important for Cisco Express Forwarding to be configured globally in the router. Unicast
RPF will not work without Cisco Express Forwarding.
Note
Restrictions
Unicast RPF should not be used on interfaces that are internal to the network. Internal interfaces are
likely to have routing asymmetry, meaning that there are multiple routes to the source of a packet.
Unicast RPF should be applied only where there is natural or configured symmetry.
For example, routers at the edge of the network of an ISP are more likely to have symmetrical reverse
paths than routers that are in the core of the ISP network. Routers that are in the core of the ISP network
have no guarantee that the best forwarding path out of the router will be the path selected for packets
returning to the router. Therefore, we do not recommend that you apply Unicast RPF where there is a
chance of asymmetric routing. It is simplest to place Unicast RPF only at the edge of a network or, for
an ISP, at the customer edge of the network.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface type number
4.
ipv6 verify unicast source reachable-via {rx | any} [allow-default] [allow-self-ping]
[access-list-name]
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Specifies an interface type and number, and places the
router in interface configuration mode.
Example:
Router(config)# interface atm 0
Step 4
ipv6 verify unicast source reachable-via {rx |
any} [allow-default] [allow-self-ping]
[access-list-name]
Example:
Router(config-if)# ipv6 verify unicast source
reachable-via any
40
Verifies that a source address exists in the FIB table and
enables Unicast RPF.
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
Mapping Hostnames to IPv6 Addresses
This task explains how to map hostnames with IPv6 addresses.
Hostname-to-Address Mappings
A name server is used to track information associated with domain names. A name server can maintain
a database of hostname-to-address mappings. Each name can map to one or more IPv4 addresses, IPv6
addresses, or both address types. In order to use this service to map domain names to IPv6 addresses,
you must specify a name server and enable the DNS—the global naming scheme of the Internet that
uniquely identifies network devices.
The Cisco IOS software maintains a cache of hostname-to-address mappings for use by the connect,
telnet, and ping commands, related Telnet support operations, and many other commands that generate
command output. This cache speeds the conversion of names to addresses.
Similar to IPv4, IPv6 uses a naming scheme that allows a network device to be identified by its location
within a hierarchical name space that provides for domains. Domain names are joined with periods (.)
as the delimiting characters. For example, Cisco is a commercial organization that is identified by a com
domain name, so its domain name is cisco.com. A specific device in this domain, the FTP server, for
example, is identified as ftp.cisco.com.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
ipv6 host name [port] ipv6-address1 [ipv6-address2...ipv6-address4]
4.
ip domain name [vrf vrf-name] name
or
ip domain list [vrf vrf-name] name
5.
ip name-server [vrf vrf-name] server-address1 [server-address2...server-address6]
6.
ip domain-lookup
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
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Step 3
Command or Action
Purpose
ipv6 host name [port] ipv6-address1
[ipv6-address2...ipv6-address4]
Defines a static hostname-to-address mapping in the
hostname cache.
•
Typically, it is easier to refer to network devices by
symbolic names rather than numerical addresses
(services such as Telnet can use hostnames or
addresses). Hostnames and IPv6 addresses can be
associated with one another through static or dynamic
means.
•
Manually assigning hostnames to addresses is useful
when dynamic mapping is not available.
Example:
Router(config)# ipv6 host cisco-sj
2001:0DB8:20:1::12
Step 4
ip domain name [vrf vrf-name] name
or
ip domain list [vrf vrf-name] name
Example:
Router(config)# ip domain-name cisco.com
(Optional) Defines a default domain name that the
Cisco IOS software will use to complete unqualified
hostnames.
or
(Optional) Defines a list of default domain names to
complete unqualified hostnames.
•
or
Example:
Router(config)# ip domain list cisco1.com
Note
Step 5
ip name-server [vrf vrf-name] server-address1
[server-address2...server-address6]
Router(config)# ip name-server
2001:0DB8::250:8bff:fee8:f800
2001:0DB8:0:f004::1
Step 6
ip domain-lookup
The ip domain name and ip domain list commands
are used to specify default domain names that can
be used by both IPv4 and IPv6.
Specifies one or more hosts that supply name information.
•
Example:
You can specify a default domain name that the
Cisco IOS software will use to complete domain name
requests. You can specify either a single domain name
or a list of domain names. Any hostname that does not
contain a complete domain name will have the default
domain name you specify appended to it before the
name is looked up.
Note
Specifies one or more hosts (up to six) that can function
as a name server to supply name information for DNS.
The server-address argument can be either an IPv4
or IPv6 address.
Enables DNS-based address translation.
•
DNS is enabled by default.
Example:
Router(config)# ip domain-lookup
Mapping IPv6 Addresses to IPv6 ATM and Frame Relay Interfaces
This task explains how to how to map IPv6 addresses to ATM and Frame Relay PVCs. Specifically, the
steps in this section explain how to explicitly map IPv6 addresses to the ATM and Frame Relay PVCs
used to reach the addresses.
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Note
This task shows how to configure both ATM and Frame Relay PVCs. Many of the steps are labeled
optional because many networks will require only one type of PVC to be configured. The steps in this
section are not applicable to ATM LANE.
IPv6 for Cisco IOS Software Support for Wide-Area Networking Technologies
IPv6 for Cisco IOS software supports wide-area networking technologies such as Cisco HDLC, PPP over
Packet over SONET (PoS), ISDN, and serial (synchronous and asynchronous) interface types, ATM
PVCs, and Frame Relay PVCs. These technologies function the same in IPv6 as they do in IPv4—IPv6
does not enhance the technologies in any way.
IPv6 Addresses and PVCs
Broadcast and multicast are used in LANs to map protocol (network-layer) addresses to the hardware
addresses of remote nodes (hosts and routers). Because using broadcast and multicast to map
network-layer addresses to hardware addresses in circuit-based WANs such as ATM and Frame Relay
networks is difficult to implement, these networks utilize implicit, explicit, and dynamic mappings for
the network-layer addresses of remote nodes and the PVCs used to reach the addresses.
Assigning an IPv6 address to an interface by using the ipv6 address command defines the IPv6
addresses for the interface and the network that is directly connected to the interface. If only one PVC
is terminated on the interface (the interface is a point-to-point interface), there is an implicit mapping
between all of the IPv6 addresses on the network and the PVC used to reach the addresses (no additional
address mappings are needed). If several PVCs are terminated on the interface (the interface is a
point-to-multipoint interface), the protocol ipv6 command (for ATM networks) or the frame-relay map
ipv6 command (for Frame Relay networks) is used to configure explicit mappings between the IPv6
addresses of the remote nodes and the PVCs used to reach the addresses.
Note
Given that IPv6 supports multiple address types, and depending on which applications or protocols are
configured on a point-to-multipoint interface, you may need to configure multiple explicit mappings
between the IPv6 addresses of the interface and the PVC used to reach the addresses. For example,
explicitly mapping both the link-local and global IPv6 address of a point-to-multipoint interface to the
PVC that the interface terminates ensures that the Interior Gateway Protocol (IGP) configured on the
interface forwards traffic to and from the PVC correctly.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
interface type number
4.
pvc [name] vpi/vci [ces | ilmi | qsaal | smds | l2transport]
5.
protocol ipv6 ipv6-address [[no] broadcast]
6.
exit
7.
ipv6 address ipv6-address/prefix-length link-local
8.
exit
9.
interface type number
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10. frame-relay map ipv6 ipv6-address dlci [broadcast] [cisco] [ietf] [payload-compression
{packet-by-packet | frf9 stac [hardware-options] | data-stream stac [hardware-options]}]
11. ipv6 address ipv6-address/prefix-length link-local
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router> enable
Step 2
configure terminal
Enters global configuration mode.
Example:
Router# configure terminal
Step 3
interface type number
Specifies an interface type and number, and places the
router in interface configuration mode.
Example:
Router(config)# interface atm 0
Step 4
pvc [name] vpi/vci [ces | ilmi | qsaal | smds
| l2transport]
(Optional) Creates or assigns a name to an ATM PVC and
places the router in ATM VC configuration mode.
Example:
Router(config-if)# pvc 1/32
Step 5
protocol ipv6 ipv6-address [[no] broadcast]
Example:
(Optional) Maps the IPv6 address of a remote node to the
PVC used to reach the address.
•
The ipv6-address argument must be in the form
documented in RFC 2373 where the address is
specified in hexadecimal using 16-bit values between
colons.
•
The optional [no] broadcast keywords indicate
whether the map entry should be used when IPv6
multicast packets (not broadcast packets) are sent to the
interface. Pseudobroadcasting is supported. The [no]
broadcast keywords in the protocol ipv6 command
take precedence over the broadcast command
configured on the same ATM PVC.
Router(config-if-atm-vc)# protocol ipv6
2001:0DB8:2222:1003::45
Step 6
exit
Example:
Router(config-if-atm-vc)# exit
44
Exits ATM VC configuration mode, and returns the router
to interface configuration mode.
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
Step 7
Command or Action
Purpose
ipv6 address ipv6-address/prefix-length
link-local
Specifies an IPv6 network assigned to the interface and
enables IPv6 processing on the interface.
•
In the context of this task, a link-local address of the
node at the other end of the link is required for the IGP
used in the network.
•
Specifying the ipv6 address link-local command
configures a link-local address on the interface that is
used instead of the link-local address that is
automatically configured when IPv6 is enabled on the
interface.
Example:
Router(config-if)# ipv6 address
2001:0DB8:2222:1003::72/64 link-local
Step 8
Exits interface configuration mode, and returns the router to
global configuration mode.
exit
Example:
Router(config-if)# exit
Step 9
interface type number
Specifies an interface type and number, and places the
router in interface configuration mode.
Example:
Router(config)# interface serial 3
Step 10
frame-relay map ipv6 ipv6-address dlci
[broadcast] [cisco] [ietf] [payload-compression
{packet-by-packet | frf9 stac
[hardware-options] | data-stream stac
[hardware-options]}]
(Optional) Maps the IPv6 address of a remote node to the
data-link connection identifier (DLCI) of the PVC used to
reach the address.
Example:
Router(config-if)# frame-relay map ipv6
FE80::E0:F727:E400:A 17 broadcast
Step 11
ipv6 address ipv6-address/prefix-length
link-local
Specifies an IPv6 network assigned to the interface and
enables IPv6 processing on the interface.
•
In the context of this task, a link-local address of the
node at the other end of the link is required for the IGP
used in the network.
•
Specifying the ipv6 address link-local command
configures a link-local address on the interface that is
used instead of the link-local address that is
automatically configured when IPv6 is enabled on the
interface.
Example:
Router(config-if)# ipv6 address
2001:0DB8:2222:1044::46/64 link-local
Displaying IPv6 Redirect Messages
This task explains how to display IPv6 redirect messages. The commands shown are optional and can be
entered in any order.
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IPv6 Redirect Messages
The IPv6 Redirect Messages feature enables a router to send ICMP IPv6 neighbor redirect messages to
inform hosts of better first hop nodes (routers or hosts) on the path to a destination.
There are no configuration tasks for the IPv6 Redirect Messages feature. The sending of IPv6 redirect
messages is enabled by default. Use the no ipv6 redirects command to disable the sending of IPv6
redirect messages on an interface. Use the ipv6 redirects command to reenable the sending of IPv6
redirect messages if the Cisco IOS software is forced to resend a packet through the same interface on
which the packet was received.
To verify whether the sending of IPv6 redirect messages is enabled on an interface, enter the show ipv6
interface command.
SUMMARY STEPS
1.
enable
2.
show ipv6 interface [brief] [type number] [prefix]
3.
show ipv6 neighbors [interface-type interface-number | ipv6-address | ipv6-hostname | statistics]
4.
show ipv6 route [ipv6-address | ipv6-prefix/prefix-length | protocol | interface-type
interface-number]
5.
show ipv6 traffic
6.
show frame-relay map [interface type number] [dlci]
7.
show atm map
8.
show hosts [vrf vrf-name | all | hostname | summary]
9.
enable
10. show running-config
DETAILED STEPS
Step 1
Command or Action
Purpose
enable
Enables privileged EXEC mode.
•
Enter your password if prompted.
Example:
Router# enable
Step 2
show ipv6 interface [brief] [type number]
[prefix]
Displays the usability status of interfaces configured for
IPv6.
•
Example:
Router# show ipv6 interface ethernet 0
Step 3
show ipv6 neighbors [interface-type
interface-number | ipv6-address | ipv6-hostname
| statistics]
Example:
Router# show ipv6 neighbors ethernet 2
46
Displays information about the status of IPv6 neighbor
redirect messages, IPv6 neighbor discovery messages,
and stateless autoconfiguration.
Displays IPv6 neighbor discovery cache information.
Implementing IPv6 Addressing and Basic Connectivity
How to Implement IPv6 Addressing and Basic Connectivity
Step 4
Command or Action
Purpose
show ipv6 route [ipv6-address |
ipv6-prefix/prefix-length | protocol |
interface-type interface-number]
(Optional) Displays the current contents of the IPv6 routing
table.
Example:
Router# show ipv6 route
Step 5
show ipv6 traffic
(Optional) Displays statistics about IPv6 traffic.
Example:
Router# show ipv6 traffic
Step 6
show frame-relay map [interface type number]
[dlci]
Displays the current map entries and information about the
Frame Relay connections.
Example:
Router# show frame-relay map
Step 7
Displays the list of all configured ATM static maps to
remote hosts on an ATM network and on ATM bundle maps.
show atm map
Example:
Router# show atm map
Step 8
show hosts [vrf vrf-name | all | hostname |
summary]
Displays the default domain name, the style of name lookup
service, a list of name server hosts, and the cached list of
hostnames and addresses.
Example:
Router# show hosts
Step 9
Enables privileged EXEC mode.
enable
•
Enter your password if prompted.
Example:
Router> enable
Step 10
show running-config
Displays the current configuration running on the router.
Example:
Router# show running-config
Examples
This section provides the following output examples:
•
Sample Output from the show ipv6 interface Command
•
Sample Output from the show ipv6 neighbors Command
•
Sample Output from the show ipv6 route Command
•
Sample Output from the show ipv6 traffic Command
•
Sample Output from the show frame-relay map Command
•
Sample Output from the show atm map Command
•
Sample Output from the show hosts Command
•
Sample Output from the show running-config Command
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Sample Output from the show ipv6 interface Command
In the following example, the show ipv6 interface command is used to verify that IPv6 addresses are
configured correctly for Ethernet interface 0. Information is also displayed about the status of IPv6
neighbor redirect messages, IPv6 neighbor discovery messages, and stateless autoconfiguration.
Router# show ipv6 interface ethernet 0
Ethernet0 is up, line protocol is up
IPv6 is stalled, link-local address is FE80::1
Global unicast address(es):
2001:0DB8:2000::1, subnet is 2001:0DB8:2000::/64
2001:0DB8:3000::1, subnet is 2001:0DB8:3000::/64
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF00:1
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds
ND advertised reachable time is 0 milliseconds
ND advertised retransmit interval is 0 milliseconds
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
Hosts use stateless autoconfig for addresses.
Sample Output from the show ipv6 neighbors Command
In the following example, the show ipv6 neighbors command is used to display IPv6 neighbor discovery
cache information. A hyphen (-) in the Age field of the command output indicates a static entry. The
following example displays IPv6 neighbor discovery cache information for Ethernet interface 2:
Router# show ipv6 neighbors ethernet 2
IPv6 Address
2001:0DB8:0:4::2
FE80::XXXX:A0FF:FED6:141E
2001:0DB8:1::45a
Age
0
0
-
Link-layer Addr
0003.a0d6.141e
0003.a0d6.141e
0002.7d1a.9472
State
REACH
REACH
REACH
Interface
Ethernet2
Ethernet2
Ethernet2
Sample Output from the show ipv6 route Command
When the ipv6-address or ipv6-prefix/prefix-length argument is specified, only route information for that
address or network is displayed. The following is sample output from the show ipv6 route command
when entered with the IPv6 prefix 2001:0DB8::/35:
Router# show ipv6 route 2001:0DB8::/35
IPv6 Routing Table - 261 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
B 2001:0DB8::/35 [20/3]
via FE80::60:5C59:9E00:16, Tunnel1
Sample Output from the show ipv6 traffic Command
In the following example, the show ipv6 traffic command is used to display ICMP rate-limited counters:
Router# show ipv6 traffic
ICMP statistics:
Rcvd: 188 input, 0 checksum errors, 0 too short
0 unknown info type, 0 unknown error type
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unreach: 0 routing, 0 admin, 0 neighbor, 0 address, 0 port
parameter: 0 error, 0 header, 0 option
0 hopcount expired, 0 reassembly timeout,0 too big
0 echo request, 0 echo reply
0 group query, 0 group report, 0 group reduce
1 router solicit, 175 router advert, 0 redirects
0 neighbor solicit, 12 neighbor advert
Sent: 7376 output, 56 rate-limited
unreach: 0 routing, 15 admin, 0 neighbor, 0 address, 0 port
parameter: 0 error, 0 header, 0 option
0 hopcount expired, 0 reassembly timeout,0 too big
15 echo request, 0 echo reply
0 group query, 0 group report, 0 group reduce
0 router solicit, 7326 router advert, 0 redirects
2 neighbor solicit, 22 neighbor advert
Sample Output from the show frame-relay map Command
In the following example, the show frame-relay map command is used to verify that the IPv6 address
of a remote node is mapped to the DLCI of the PVC used to reach the address. The following example
shows that the link-local and global IPv6 addresses (FE80::E0:F727:E400:A and
2001:0DB8:2222:1044::73; FE80::60:3E47:AC8:8 and 2001.0DB8:2222:1044::72) of two remote nodes
are explicitly mapped to DLCI 17 and DLCI 19, respectively. Both DLCI 17 and DLCI 19 are terminated
on interface serial 3 of this node; therefore, interface serial 3 of this node is a point-to-multipoint
interface.
Router# show frame-relay map
Serial3 (up): ipv6 FE80::E0:F727:E400:A dlci 17(0x11,0x410), static,
broadcast, CISCO, status defined, active
Serial3 (up): ipv6 2001:0DB8:2222:1044::72 dlci 19(0x13,0x430), static,
CISCO, status defined, active
Serial3 (up): ipv6 2001:0DB8:2222:1044::73 dlci 17(0x11,0x410), static,
CISCO, status defined, active
Serial3 (up): ipv6 FE80::60:3E47:AC8:8 dlci 19(0x13,0x430), static,
broadcast, CISCO, status defined, active
Sample Output from the show atm map Command
In the following example, the show atm map command is used to verify that the IPv6 address of a
remote node is mapped to the PVC used to reach the address. The following example shows that the
link-local and global IPv6 addresses (FE80::60:3E47:AC8:C and 2001:0DB8:2222:1003::72,
respectively) of a remote node are explicitly mapped to PVC 1/32 of ATM interface 0:
Router# show atm map
Map list ATM0pvc1 : PERMANENT
ipv6 FE80::60:3E47:AC8:C maps to VC 1, VPI 1, VCI 32, ATM0
, broadcast
ipv6 2001:0DB8:2222:1003::72 maps to VC 1, VPI 1, VCI 32, ATM0
Sample Output from the show hosts Command
The state of the name lookup system on the DHCP for IPv6 client can be displayed with the show hosts
command:
Router# show hosts
Default domain is not set
Domain list:example.com
Name/address lookup uses domain service
Name servers are 2001:0DB8:A:B::1, 2001:0DB8:3000:3000::42
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Codes:UN - unknown, EX - expired, OK - OK, ?? - revalidate
temp - temporary, perm - permanent
NA - Not Applicable None - Not defined
Host
sdfasfd
Port
None
Flags
Age Type
(temp, UN) 0 IPv6
Address(es)
Sample Output from the show running-config Command
In the following example, the show running-config command is used to verify that IPv6 processing of
packets is enabled globally on the router and on applicable interfaces, and that an IPv6 address is
configured on applicable interfaces:
Router# show running-config
Building configuration...
Current configuration : 22324 bytes
!
! Last configuration change at 14:59:38 PST Tue Jan 16 2001
! NVRAM config last updated at 04:25:39 PST Tue Jan 16 2001 by bird
!
hostname Router
!
ipv6 unicast-routing
!
interface Ethernet0
no ip route-cache
no ip mroute-cache
no keepalive
media-type 10BaseT
ipv6 address 2001:0DB8:0:1::/64 eui-64
!
In the following example, the show running-config command is used to verify that Cisco Express
Forwarding and network accounting for Cisco Express Forwarding have been enabled globally on a
nondistributed architecture platform, and that Cisco Express Forwarding has been enabled on an IPv6
interface. The following output shows that both that Cisco Express Forwarding and network accounting
for Cisco Express Forwarding have been enabled globally on the router, and that Cisco Express
Forwarding has also been enabled on Ethernet interface 0:
Router# show running-config
Building configuration...
Current configuration : 22324 bytes
!
! Last configuration change at 14:59:38 PST Tue Jan 16 2001
! NVRAM config last updated at 04:25:39 PST Tue Jan 16 2001 by bird
!
hostname Router
!
ip cef
ipv6 unicast-routing
ipv6 cef
ipv6 cef accounting prefix-length
!
!
interface Ethernet0
ip address 10.4.9.11 255.0.0.0
media-type 10BaseT
ipv6 address 2001:0DB8:C18:1::/64 eui-64
!
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Configuration Examples for Implementing IPv6 Addressing and Basic Connectivity
In the following example, the show running-config command is used to verify that distributed
Cisco Express Forwarding and network accounting for distributed Cisco Express Forwarding have been
enabled globally on a distributed architecture platform, such as the Cisco 7500 series routers. The
following example shows that both distributed Cisco Express Forwarding and network accounting for
Cisco Express Forwarding have been enabled globally on the router.
Note
Distributed Cisco Express Forwarding is enabled by default on the Cisco 12000 series Internet routers
and disabled by default on the Cisco 7500 series routers. Therefore, output from the show
running-config command on the Cisco 12000 series does not show whether distributed Cisco Express
Forwarding is configured globally on the router. The following output is from a Cisco 7500 series router.
Router# show running-config
Building configuration...
Current configuration : 22324 bytes
!
! Last configuration change at 14:59:38 PST Tue Jan 16 2001
! NVRAM config last updated at 04:25:39 PST Tue Jan 16 2001 by bird
!
hostname Router
!
ip cef distributed
ipv6 unicast-routing
ipv6 cef distributed
ipv6 cef accounting prefix-length
In the following example, the show running-config command is used to verify static
hostname-to-address mappings, default domain names, and name servers in the hostname cache, and to
verify that the DNS service is enabled:
Router# show running-config
Building configuration...
!
ipv6 host cisco-sj 2001:0DB8:20:1::12
!
ip domain-name cisco.com
ip domain-lookup
ip name-server 2001:0DB8:C01F:768::1
Configuration Examples for Implementing IPv6 Addressing and
Basic Connectivity
This section provides the following configuration examples:
•
IPv6 Addressing and IPv6 Routing Configuration: Example, page 52
•
Dual Protocol Stacks Configuration: Example, page 52
•
IPv6 ICMP Rate Limiting Configuration: Example, page 52
•
Cisco Express Forwarding and Distributed Cisco Express Forwarding Configuration: Example,
page 53
•
Hostname-to-Address Mappings Configuration: Example, page 53
•
IPv6 Address to ATM and Frame Relay PVC Mapping Configuration: Examples, page 53
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Configuration Examples for Implementing IPv6 Addressing and Basic Connectivity
IPv6 Addressing and IPv6 Routing Configuration: Example
In the following example, IPv6 is enabled on the router with both a link-local address and a global
address based on the IPv6 prefix 2001:0DB8:c18:1::/64. The EUI-64 interface ID is used in the
low-order 64 bits of both addresses. Output from the show ipv6 interface command is included to show
how the interface ID (260:3EFF:FE47:1530) is appended to the link-local prefix FE80::/64 of Ethernet
interface 0.
ipv6 unicast-routing
interface ethernet 0
ipv6 address 2001:0DB8:c18:1::/64 eui-64
Router# show ipv6 interface ethernet 0
Ethernet0 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::260:3EFF:FE47:1530
Global unicast address(es):
2001:0DB8:C18:1:260:3EFF:FE47:1530, subnet is 2001:0DB8:C18:1::/64
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF47:1530
FF02::9
MTU is 1500 bytes
ICMP error messages limited to one every 500 milliseconds
ND reachable time is 30000 milliseconds
ND advertised reachable time is 0 milliseconds
ND advertised retransmit interval is 0 milliseconds
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
Hosts use stateless autoconfig for addresses.
In the following example, multiple IPv6 global addresses within the prefix 2001:0DB8::/64 are
configured on Ethernet interface 0:
interface ethernet 0
ipv6 address 2001:0DB8::1/64
ipv6 address 2001:0DB8::/64 eui-64
Dual Protocol Stacks Configuration: Example
The following example enables the forwarding of IPv6 unicast datagrams globally on the router and
configures Ethernet interface 0 with both an IPv4 address and an IPv6 address:
ipv6 unicast-routing
interface Ethernet0
ip address 192.168.99.1 255.255.255.0
ipv6 address 2001:0DB8:c18:1::3/64
IPv6 ICMP Rate Limiting Configuration: Example
The following example shows an interval of 50 milliseconds and a bucket size of 20 tokens being
configured for IPv6 ICMP error messages:
ipv6 icmp error-interval 50 20
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Configuration Examples for Implementing IPv6 Addressing and Basic Connectivity
Cisco Express Forwarding and Distributed Cisco Express Forwarding
Configuration: Example
In the following example, both Cisco Express Forwarding for IPv6 and network accounting for Cisco
Express Forwarding for IPv6 have been enabled globally on a nondistributed architecture router, and
Cisco Express Forwarding for IPv6 has been enabled on Ethernet interface 0. The example also shows
that the forwarding of IPv6 unicast datagrams has been configured globally on the router with the ipv6
unicast-routing command, an IPv6 address has been configured on Ethernet interface 0 with the ipv6
address command, and Cisco Express Forwarding for IPv4 has been configured globally on the router
with the ip cef command.
ip cef
ipv6 unicast-routing
ipv6 cef
ipv6 cef accounting prefix-length
interface Ethernet0
ip address 10.4.9.11 255.0.0.0
media-type 10BaseT
ipv6 address 2001:0DB8:C18:1::/64 eui-64
In the following example, both distributed Cisco Express Forwarding for IPv6 and network accounting
for distributed Cisco Express Forwarding for IPv6 have been enabled globally on a distributed
architecture router. The forwarding of IPv6 unicast datagrams has been configured globally on the router
with the ipv6 unicast-routing command and distributed Cisco Express Forwarding for IPv4 has been
configured globally on the router with the ip cef distributed command.
ip cef distributed
ipv6 unicast-routing
ipv6 cef distributed
ipv6 cef accounting prefix-length
Hostname-to-Address Mappings Configuration: Example
The following example defines two static hostname-to-address mappings in the hostname cache,
establishes a domain list with several alternate domain names to complete unqualified hostnames,
specifies host 2001:0DB8::250:8bff:fee8:f800 and host 2001:0DB8:0:f004::1 as the name servers, and
reenables the DNS service:
ipv6 host cisco-sj 2001:0DB8:700:20:1::12
ipv6 host cisco-hq 2001:0DB8:768::1 2001:0DB8:20:1::22
ip domain list example1.com
ip domain list example2.com
ip domain list example3.edu
ip name-server 2001:0DB8::250:8bff:fee8:f800 2001:0DB8:0:f004::1
ip domain-lookup
IPv6 Address to ATM and Frame Relay PVC Mapping Configuration: Examples
This section provides the following IPv6 ATM and Frame Relay PVC mapping configuration examples:
•
IPv6 ATM PVC Mapping Configuration—Point-to-Point Interface: Example
•
IPv6 ATM PVC Mapping Configuration—Point-to-Multipoint Interface: Example
•
IPv6 Frame Relay PVC Mapping Configuration—Point-to-Point Interface: Example
53
Implementing IPv6 Addressing and Basic Connectivity
Configuration Examples for Implementing IPv6 Addressing and Basic Connectivity
•
IPv6 Frame Relay PVC Mapping Configuration—Point-to-Multipoint Interface: Example
IPv6 ATM PVC Mapping Configuration—Point-to-Point Interface: Example
In the following example, two nodes named Router 1 and Router 2 are connected by a single PVC. The
point-to-point subinterface ATM0.132 is used on both nodes to terminate the PVC; therefore, the
mapping between the IPv6 addresses of both nodes and the PVC is implicit (no additional mappings are
required).
Router 1 Configuration
interface ATM 0
no ip address
!
interface ATM 0.132 point-to-point
pvc 1/32
encapsulation aal5snap
!
ipv6 address 2001:0DB8:2222:1003::72/64
Router 2 Configuration
interface ATM 0
no ip address
!
interface ATM 0.132 point-to-point
pvc 1/32
encapsulation aal5snap
!
ipv6 address 2001:0DB8:2222:1003::45/64
IPv6 ATM PVC Mapping Configuration—Point-to-Multipoint Interface: Example
In the following example, the same two nodes (Router 1 and Router 2) from the previous example are
connected by the same PVC. In this example, however, the point-to-multipoint interface ATM0 is used
on both nodes to terminate the PVC; therefore, explicit mappings are required between the link-local and
global IPv6 addresses of interface ATM0 on both nodes and the PVC. Additionally, ATM
pseudobroadcasts are enabled on the link-local address of interface ATM0 on both nodes. The link-local
address specified here is the link-local address of the other end of the PVC.
Router 1 Configuration
interface ATM 0
no ip address
pvc 1/32
protocol ipv6 2001:0DB8:2222:1003::45
protocol ipv6 FE80::60:2FA4:8291:2 broadcast
encapsulation aal5snap
!
ipv6 address 2001:0DB8:2222:1003::72/64
Router 2 Configuration
interface ATM 0
no ip address
pvc 1/32
protocol ipv6 FE80::60:3E47:AC8:C broadcast
protocol ipv6 2001:0DB8:2222:1003::72
encapsulation aal5snap
!
54
Implementing IPv6 Addressing and Basic Connectivity
Configuration Examples for Implementing IPv6 Addressing and Basic Connectivity
ipv6 address 2001:0DB8:2222:1003::45/64
IPv6 Frame Relay PVC Mapping Configuration—Point-to-Point Interface: Example
In the following example, three nodes named Router A, Router B, and Router C make up a fully meshed
network. Each node is configured with two PVCs, which provide an individual connection to each of the
other two nodes. Each PVC is configured on a different point-to-point subinterface, which creates three
unique IPv6 networks (2001:0DB8:2222:1017:/64, 2001:0DB8:2222:1018::/64, and
2001:0DB8:2222:1019::/64). Therefore, the mappings between the IPv6 addresses of each node and the
DLCI (DLCI 17, 18, and 19) of the PVC used to reach the addresses are implicit (no additional mappings
are required).
Note
Given that each PVC in the following example is configured on a different point-to-point subinterface,
the configuration in the following example can also be used in a network that is not fully meshed.
Additionally, configuring each PVC on a different point-to-point subinterface can help simplify your
routing protocol configuration. However, the configuration in the following example requires more than
one IPv6 network, whereas configuring each PVC on point-to-multipoint interfaces requires only one
IPv6 network.
Router A Configuration
interface Serial 3
encapsulation frame-relay
!
interface Serial3.17 point-to-point
description to Router B
ipv6 address 2001:0DB8:2222:1017::46/64
frame-relay interface-dlci 17
!
interface Serial 3.19 point-to-point
description to Router C
ipv6 address 2001:0DB8:2222:1019::46/64
frame-relay interface-dlci 19
Router B Configuration
interface Serial 5
encapsulation frame-relay
!
interface Serial5.17 point-to-point
description to Router A
ipv6 address 2001:0DB8:2222:1017::73/64
frame-relay interface-dlci 17
!
interface Serial5.18 point-to-point
description to Router C
ipv6 address 2001:0DB8:2222:1018::73/64
frame-relay interface-dlci 18
Router C Configuration
interface Serial 0
encapsulation frame-relay
!
interface Serial0.18 point-to-point
description to Router B
ipv6 address 2001:0DB8:2222:1018::72/64
frame-relay interface-dlci 18
!
55
Implementing IPv6 Addressing and Basic Connectivity
Where to Go Next
interface Serial0.19 point-to-point
description to Router A
ipv6 address 2001:0DB8:2222:1019::72/64
frame-relay interface-dlci 19
IPv6 Frame Relay PVC Mapping Configuration—Point-to-Multipoint Interface: Example
In the following example, the same three nodes (Router A, Router B, and Router C) from the previous
example make up a fully meshed network and each node is configured with two PVCs (which provide
an individual connection to each of the other two nodes). However, the two PVCs on each node in the
following example are configured on a single interface (serial 3, serial 5, and serial 10, respectively),
which makes each interface a point-to-multipoint interface. Therefore, explicit mappings are required
between the link-local and global IPv6 addresses of each interface on all three nodes and the DLCI
(DLCI 17, 18, and 19) of the PVC used to reach the addresses.
Router A Configuration
interface Serial 3
encapsulation frame-relay
ipv6 address 2001:0DB8:2222:1044::46/64
frame-relay map ipv6 FE80::E0:F727:E400:A 17 broadcast
frame-relay map ipv6 FE80::60:3E47:AC8:8 19 broadcast
frame-relay map ipv6 2001:0DB8:2222:1044::72 19
frame-relay map ipv6 2001:0DB8:2222:1044::73 17
Router B Configuration
interface Serial 5
encapsulation frame-relay
ipv6 address 2001:0DB8:2222:1044::73/64
frame-relay map ipv6 FE80::60:3E59:DA78:C 17 broadcast
frame-relay map ipv6 FE80::60:3E47:AC8:8 18 broadcast
frame-relay map ipv6 2001:0DB8:2222:1044::46 17
frame-relay map ipv6 2001:0DB8:2222:1044::72 18
Router C Configuration
interface Serial 10
encapsulation frame-relay
ipv6 address 2001:0DB8:2222:1044::72/64
frame-relay map ipv6 FE80::60:3E59:DA78:C 19
frame-relay map ipv6 FE80::E0:F727:E400:A 18
frame-relay map ipv6 2001:0DB8:2222:1044::46
frame-relay map ipv6 2001:0DB8:2222:1044::73
broadcast
broadcast
19
18
Where to Go Next
If you want to implement IPv6 routing protocols, see the Implementing RIP for IPv6, Implementing IS-IS
for IPv6, or Implementing Multiprotocol BGP for IPv6 module.
56
Implementing IPv6 Addressing and Basic Connectivity
Additional References
Additional References
The following sections provide references related to the Implementing IPv6 Addressing and Basic
Connectivity feature.
Related Documents
Related Topic
Document Title
IPv6 supported feature list
“Start Here: Cisco IOS Software Release Specifics for IPv6
Features,” Cisco IOS IPv6 Configuration Guide
IPv6 commands: complete command syntax, command Cisco IOS IPv6 Command Reference
mode, defaults, usage guidelines, and examples
IPv6 DHCP description and configuration
“Implementing DHCP for IPv6,” Cisco IOS IPv6 Configuration
Guide
IPv4 addressing configuration tasks
“Configuring IPv4 Addresses,” Cisco IOS IP Addressing Services
Configuration Guide
IPv4 services configuration tasks
“Configuring IP Services,” Cisco IOS IP Application Services
Configuration Guide
IPv4 addressing commands
Cisco IOS IP Addressing Services Command Reference
IPv4 IP services commands
Cisco IOS IP Application Services Command Reference
Stateful switchover
“Stateful Switchover,” Cisco IOS High Availability Configuration
Guide
Switching configuration tasks
“Cisco IOS IP Switching Features Roadmap,” Cisco IOS IP
Switching Configuration Guide
Switching commands
Cisco IOS IP Switching Command Reference
Standards
Standards
Title
No new or modified standards are supported by this
—
feature, and support for existing standards has not been
modified by this feature.
MIBs
MIBs
MIBs Link
No new or modified MIBs are supported, and support
for existing MIBs has not been modified.
To locate and download MIBs for selected platforms, Cisco IOS
releases, and feature sets, use Cisco MIB Locator found at the
following URL:
http://www.cisco.com/go/mibs
57
Implementing IPv6 Addressing and Basic Connectivity
Additional References
RFCs
RFCs
Title
RFC 1981
Path MTU Discovery for IP version 6
RFC 2373
IP Version 6 Addressing Architecture
RFC 2374
An Aggregatable Global Unicast Address Format
RFC 2460
Internet Protocol, Version 6 (IPv6) Specification
RFC 2461
Neighbor Discovery for IP Version 6 (IPv6)
RFC 2462
IPv6 Stateless Address Autoconfiguration
RFC 2463
Internet Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification
RFC 2464
Transmission of IPv6 Packets over Ethernet Networks
RFC 2467
Transmission of IPv6 Packets over FDDI Networks
RFC 2472
IP Version 6 over PPP
RFC 2492
IPv6 over ATM Networks
RFC 2590
Transmission of IPv6 Packets over Frame Relay Networks
Specification
RFC 3152
Delegation of IP6.ARPA
RFC 3162
RADIUS and IPv6
RFC 3513
Internet Protocol Version 6 (IPv6) Addressing Architecture
RFC 3596
DNS Extensions to Support IP version 6
RFC 3879
Deprecating Site Local Addresses
RFC 4193
Unique Local IPv6 Unicast Addresses
Technical Assistance
Description
Link
The Cisco Support website provides extensive online
resources, including documentation and tools for
troubleshooting and resolving technical issues with
Cisco products and technologies.
http://www.cisco.com/techsupport
To receive security and technical information about
your products, you can subscribe to various services,
such as the Product Alert Tool (accessed from Field
Notices), the Cisco Technical Services Newsletter, and
Really Simple Syndication (RSS) Feeds.
Access to most tools on the Cisco Support website
requires a Cisco.com user ID and password.
58
Implementing IPv6 Addressing and Basic Connectivity
Command Reference
Command Reference
The following commands are introduced or modified in the feature or features documented in this
module. For information about these commands, see the Cisco IOS IPv6 Command Reference at
http://www.cisco.com/en/US/docs/ios/ipv6/command/reference/ipv6_book.html. For information about
all Cisco IOS commands, use the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup
or the Cisco IOS Master Command List, All Releases, at
http://www.cisco.com/en/US/docs/ios/mcl/all_release/all_mcl.html.
•
atm route-bridged
•
cef table consistency-check
•
clear cef table
•
clear ipv6 neighbors
•
clear ipv6 route
•
clear ipv6 traffic
•
copy
•
debug adjacency
•
debug ipv6 cef drop
•
debug ipv6 cef events
•
debug ipv6 cef hash
•
debug ipv6 cef receive
•
debug ipv6 cef table
•
debug ipv6 icmp
•
debug ipv6 nd
•
debug ipv6 packet
•
debug ipv6 routing
•
frame-relay map ipv6
•
ip name-server
•
ipv6 address
•
ipv6 address anycast
•
ipv6 address eui-64
•
ipv6 address link-local
•
ipv6 atm-vc
•
ipv6 cef
•
ipv6 cef accounting
•
ipv6 cef distributed
•
ipv6 enable
•
ipv6 general-prefix
•
ipv6 hop-limit
•
ipv6 icmp error-interval
59
Implementing IPv6 Addressing and Basic Connectivity
Command Reference
60
•
ipv6 mtu
•
ipv6 nd dad attempts
•
ipv6 nd managed-config-flag
•
ipv6 nd ns-interval
•
ipv6 nd prefix
•
ipv6 nd prefix-advertisement
•
ipv6 nd ra interval
•
ipv6 nd ra lifetime
•
ipv6 nd ra suppress
•
ipv6 nd reachable-time
•
ipv6 nd router-preference
•
ipv6 neighbor
•
ipv6 redirects
•
ipv6 unicast-routing
•
ipv6 unnumbered
•
ipv6 verify unicast reverse-path
•
ipv6 verify unicast source reachable-via
•
logging host
•
logging origin-id
•
logging source-interface
•
neighbor activate
•
neighbor override-capability-neg
•
neighbor send-label
•
neighbor translate-update
•
neighbor update-source
•
ping
•
ping ipv6
•
protocol ipv6 (ATM)
•
show adjacency
•
show atm map
•
show cdp entry
•
show cdp neighbors
•
show cef
•
show cef interface
•
show cef linecard
•
show frame-relay map
•
show ipv6 cef
•
show ipv6 cef adjacency
Implementing IPv6 Addressing and Basic Connectivity
Command Reference
•
show ipv6 cef non-recursive
•
show ipv6 cef summary
•
show ipv6 cef switching statistics
•
show ipv6 cef traffic prefix-length
•
show ipv6 cef tree
•
show ipv6 cef unresolved
•
show ipv6 general-prefix
•
show ipv6 interface
•
show ipv6 mtu
•
show ipv6 neighbors
61
Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and
Basic Connectivity
Table 5 lists the features in this module and provides links to specific configuration information. Only
features that were introduced or modified in Cisco IOS Release 12.2(2)T or a later release appear in the
table.
For information on a feature in this technology that is not documented here, see the Start Here:
Cisco IOS Software Release Specifies for IPv6 Features roadmap.
Not all commands may be available in your Cisco IOS software release. For release information about a
specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support.
Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images
support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to
http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
62
Table 5 lists only the Cisco IOS software release that introduced support for a given feature in a given
Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS
software release train also support that feature.
Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Table 5
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Feature Name
Releases
Feature Information
IPv6: ICMPv6
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
ICMP for IPv6 generates error messages, such as ICMP
destination unreachable messages, and informational
messages, such as ICMP echo request and reply messages.
Additionally, ICMP packets in IPv6 are used in the IPv6
neighbor discovery process, path MTU discovery, and the
MLD protocol for IPv6.
IPv6: ICMPv6 redirect
IPv6: ICMP rate limiting
The following sections provide information about this
feature:
•
ICMP for IPv6, page 18
•
IPv6 Neighbor Discovery, page 18
•
IPv6 Neighbor Solicitation Message, page 19
•
IPv6 Router Advertisement Message, page 21
•
IPv6 Stateless Autoconfiguration, page 24
•
Configuring IPv6 ICMP Rate Limiting, page 34
•
IPv6 ICMP Rate Limiting Configuration: Example,
page 52
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(4)T
12.3
12.3(2)T
12.4
12.4(2)T
A value of 137 in the Type field of the ICMP packet header
identifies an IPv6 neighbor redirect message. Routers send
neighbor redirect messages to inform hosts of better
first-hop nodes on the path to a destination.
12.2(8)T
12.3
12.3(2)T
12.4
12.4(2)T
The IPv6 ICMP rate limiting feature implements a token
bucket algorithm for limiting the rate at which IPv6 ICMP
error messages are sent out on the network.
The following sections provide information about this
feature:
•
IPv6 Neighbor Redirect Message, page 22
•
IPv6 Redirect Messages, page 46
The following sections provide information about this
feature:
•
Configuring IPv6 ICMP Rate Limiting, page 34
•
IPv6 ICMP Rate Limiting, page 34
•
IPv6 ICMP Rate Limiting Configuration: Example,
page 52
63
Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Table 5
Feature Information for Implementing IPv6 Addressing and Basic Connectivity (continued)
Feature Name
Releases
Feature Information
IPv6: IPv6 default router preferences
12.2(33)SB
12.2(33)SRA
12.4(2)T
12.2(33)SXH
The DRP extension provides a coarse preference metric
(low, medium, or high) for default routers.
IPv6: IPv6 MTU path discovery
IPv6: IPv6 neighbor discovery
IPv6: IPv6 neighbor discovery duplicate
address detection
64
The following sections provide information about this
feature:
•
Default Router Preferences for Traffic Engineering,
page 22
•
Configuring the DRP Extension for Traffic
Engineering, page 35
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
Path MTU discovery in IPv6 allows a host to dynamically
discover and adjust to differences in the MTU size of every
link along a given data path.
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
The IPv6 neighbor discovery process uses ICMP messages
and solicited-node multicast addresses to determine the
link-layer address of a neighbor on the same network (local
link), verify the reachability of a neighbor, and track
neighboring routers.
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(4)T
12.3
12.3(2)T
12.4
12.4(2)T
The following sections provide information about this
feature:
•
Path MTU Discovery for IPv6, page 17
•
ICMP for IPv6, page 18
The following sections provide information about this
feature:
•
Link-Local Address, page 7
•
ICMP for IPv6, page 18
•
IPv6 Neighbor Discovery, page 18
•
IPv6 Multicast Groups, page 28
IPv6 neighbor discovery duplicate address detection is
performed first on a new, link-local IPv6 address before the
address is assigned to an interface (the new address remains
in a tentative state while duplicate address detection is
performed).
The following sections provide information about this
feature:
•
IPv6 Neighbor Solicitation Message, page 19
•
IPv6 Stateless Autoconfiguration, page 24
Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Table 5
Feature Information for Implementing IPv6 Addressing and Basic Connectivity (continued)
Feature Name
Releases
Feature Information
IPv6: IPv6 stateless autoconfiguration
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
The IPv6 stateless autoconfiguration feature can be used to
manage link, subnet, and site addressing changes.
IPv6: IPv6 static cache entry for neighbor
discovery
IPv6 access services: Remote bridged
encapsulation (RBE)
The following sections provide information about this
feature:
•
Link-Local Address, page 7
•
IPv6 Neighbor Solicitation Message, page 19
•
IPv6 Router Advertisement Message, page 21
•
IPv6 Stateless Autoconfiguration, page 24
•
Simplified Network Renumbering for IPv6 Hosts,
page 24
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(33)SRA
12.2(8)T
12.3
12.3(2)T
12.4
12.4(2)T
The IPv6 static cache entry for neighbor discovery feature
allows static entries to be made in the IPv6 neighbor cache.
12.3(4)T
12.4
12.4(2)T
RBE provides a mechanism for routing a protocol from a
bridged interface to another routed or bridged interface.
The following section provides information about this
feature:
•
The following section provides information about this
feature:
•
IPv6: Anycast Address
12.2(25)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(33)SXH
12.3(4)T
12.4
12.4(2)T
IPv6 Neighbor Discovery, page 18
Routed Bridge Encapsulation for IPv6, page 26
An anycast address is an address that is assigned to a set of
interfaces that typically belong to different nodes.
The following sections provide information about this
feature:
•
IPv6 Address Type: Anycast, page 9
•
IPv6 Address Type: Multicast, page 10
•
IPv6 Multicast Groups, page 28
•
Configuring IPv6 Addressing and Enabling IPv6
Routing, page 28
65
Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Table 5
Feature Information for Implementing IPv6 Addressing and Basic Connectivity (continued)
Feature Name
Releases
Feature Information
IPv6 address types: Unicast
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
An IPv6 unicast address is an identifier for a single
interface, on a single node.
Unicast Reverse Path Forwarding for IPv6
12.0(31)S
The following sections provide information about this
feature:
•
IPv6 Address Formats, page 4
•
IPv6 Address Type: Unicast, page 5
•
IPv6 Address Type: Anycast, page 9
•
IPv6 Address Type: Multicast, page 10
•
IPv6 Neighbor Solicitation Message, page 19
•
IPv6 Router Advertisement Message, page 21
•
Configuring IPv6 Addressing and Enabling IPv6
Routing, page 28
The Unicast RPF feature mitigates problems caused by
malformed or forged (spoofed) IPv6 source addresses that
pass through an IPv6 router.
The following sections provide information about this
feature:
IPv6 data link: ATM PVC and ATM LANE
IPv6 data link: Cisco High-Level Data Link
Control (HDLC)
66
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
•
Prerequisites for Implementing IPv6 Addressing and
Basic Connectivity, page 2
•
Unicast Reverse Path Forwarding, page 16
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. ATM PVC and ATM LANE are
data links supported for IPv6.
The following sections provide information about this
feature:
•
IPv6 Data Links, page 26
•
Configuring Cisco Express Forwarding and Distributed
Cisco Express Forwarding Switching for IPv6, page 36
•
Mapping IPv6 Addresses to IPv6 ATM and Frame
Relay Interfaces, page 42
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. HDLC is a type of data link
supported for IPv6.
The following sections provide information about this
feature:
•
IPv6 Data Links, page 26
•
Configuring Cisco Express Forwarding and Distributed
Cisco Express Forwarding Switching for IPv6, page 36
•
Mapping IPv6 Addresses to IPv6 ATM and Frame
Relay Interfaces, page 42
Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Table 5
Feature Information for Implementing IPv6 Addressing and Basic Connectivity (continued)
Feature Name
Releases
IPv6 data link: Dynamic packet transport (DPT) 12.0(23)S
Feature Information
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. DPT is a type of data link
supported for IPv6.
The following section provides information about this
feature:
•
IPv6 Data Links, page 26
IPv6 data link: Ethernet, Fast Ethernet, Gigabit 12.0(22)S
Ethernet, and 10-Gigabit Ethernet
12.2(14)S
12.2(28)SB
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. Ethernet, Fast Ethernet, Gigabit
Ethernet, and 10-Gigabit Ethernet are data links supported
for IPv6.
IPv6 data link: FDDI
12.2(14)S
12.2(28)SB
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. FDDI is a type of data link
supported for IPv6.
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. Frame relay PVC is a type of
data link supported for IPv6.
IPv6 data link: Frame Relay PVC
The following sections provide information about this
feature:
•
IPv6 Data Links, page 26
•
Configuring Cisco Express Forwarding and Distributed
Cisco Express Forwarding Switching for IPv6, page 36
The following sections provide information about this
feature:
•
IPv6 Data Links, page 26
•
Configuring Cisco Express Forwarding and Distributed
Cisco Express Forwarding Switching for IPv6, page 36
The following sections provide information about this
feature:
•
IPv6 Data Links, page 26
•
Configuring Cisco Express Forwarding and Distributed
Cisco Express Forwarding Switching for IPv6, page 36
•
Mapping IPv6 Addresses to IPv6 ATM and Frame
Relay Interfaces, page 42
67
Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Table 5
Feature Information for Implementing IPv6 Addressing and Basic Connectivity (continued)
Feature Name
Releases
Feature Information
IPv6 data link: PPP service over Packet over
SONET, ISDN, and serial (synchronous and
asynchronous) interfaces
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. PPP service over Packet over
SONET, ISDN, and serial interfaces is a type of data link
supported for IPv6.
IPv6 data link: VLANs using
Cisco Inter-Switch Link (ISL)
IPv6 data link: VLANs using IEEE 802.1Q
encapsulation
IPv6 services: AAAA DNS lookups over an
IPv4 transport
68
The following sections provide information about this
feature:
•
IPv6 Data Links, page 26
•
Configuring Cisco Express Forwarding and Distributed
Cisco Express Forwarding Switching for IPv6, page 36
•
Mapping IPv6 Addresses to IPv6 ATM and Frame
Relay Interfaces, page 42
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. VLANs using Cisco ISL is a
type of data link supported for IPv6.
12.0(22)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(14)S
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
In IPv6 networks, a data link is a network sharing a
particular link-local prefix. VLANs using IEEE 802.1Q
encapsulation is a type of data link supported for IPv6.
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
IPv6 basic connectivity can be enhanced by configuring
support for AAAA record types in the DNS
name-to-address and address-to-name lookup processes.
The following section provides information about this
feature:
•
IPv6 Data Links, page 26
The following section provides information about this
feature:
•
IPv6 Data Links, page 26
The following section provides information about this
feature:
•
DNS for IPv6, page 17
Implementing IPv6 Addressing and Basic Connectivity
Feature Information for Implementing IPv6 Addressing and Basic Connectivity
Table 5
Feature Information for Implementing IPv6 Addressing and Basic Connectivity (continued)
Feature Name
Releases
Feature Information
IPv6 services: Cisco Discovery Protocol—IPv6 12.2(14)S
address family support for neighbor information 12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(8)T
12.3
12.3(2)T
12.4
12.4(2)T
The Cisco Discovery Protocol IPv6 address support for
neighbor information feature adds the ability to transfer
IPv6 addressing information between two Cisco devices.
IPv6 services: DNS lookups over an IPv6
transport
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(8)T
12.3
12.3(2)T
12.4
12.4(2)T
IPv6 supports DNS record types that are supported in the
DNS name-to-address and address-to-name lookup
processes.
12.3(4)T
12.4
12.4(2)T
The upper 64 bits of an IPv6 address are composed from a
global routing prefix plus a subnet ID. A general prefix (for
example, /48) holds a short prefix, based on which a number
of longer, more specific, prefixes (for example, /64) can be
defined.
IPv6 services: generic prefix
The following section provides information about this
feature:
•
Cisco Discovery Protocol IPv6 Address Support,
page 17
The following section provides information about this
feature:
•
DNS for IPv6, page 17
The following sections provide information about this
feature:
IPv6 switching: Cisco Express Forwarding and 12.0(21)ST
distributed Cisco Express Forwarding support 12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(13)T
12.3
12.3(2)T
12.4
12.4(2)T
•
IPv6 General Prefixes, page 25
•
Defining and Using IPv6 General Prefixes, page 30
Cisco Express Forwarding for IPv6 is advanced, Layer 3 IP
switching technology for the forwarding of IPv6 packets.
Distributed Cisco Express Forwarding for IPv6 performs
the same functions as CEFv6 but for distributed architecture
platforms such as the Cisco 12000 series Internet routers
and the Cisco 7500 series routers.
The following sections provide information about this
feature:
•
Cisco Express Forwarding and Distributed Cisco
Express Forwarding Switching for IPv6, page 15
•
Configuring Cisco Express Forwarding and Distributed
Cisco Express Forwarding Switching for IPv6, page 36
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Feature Information for Implementing IPv6 Addressing and Basic Connectivity
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