IPv6 Routing: IS-IS Support for IPv6
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Contents
IPv6 Routing: IS-IS Support for IPv6Last Updated: May 1, 2012
This module describes how to configure Integrated Intermediate System-to-Intermediate System (IS-IS) for IPv6. IS-IS is an Interior Gateway Protocol (IGP) that advertises link-state information throughout the network to create a picture of the network topology. IS-IS is an Open Systems Interconnection (OSI) hierarchical routing protocol that designates an intermediate system as a Level 1 or Level 2 device. Level 2 devices route between Level 1 areas to create an intradomain routing backbone. Integrated IS-IS uses a single routing algorithm to support several network address families, such as IPv6, IPv4, and OSI. Finding Feature InformationYour 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 Table at the end of this document. Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required. Information About IPv6 Routing: IS-IS Support for IPv6IS-IS Enhancements for IPv6IS-IS in IPv6 functions the same and offers many of the same benefits as IS-IS in IPv4. IPv6 enhancements to IS-IS allow IS-IS to advertise IPv6 prefixes in addition to IPv4 and OSI routes. Extensions to the IS-IS command-line interface (CLI) allow configuration of IPv6-specific parameters. IPv6 IS-IS extends the address families supported by IS-IS to include IPv6, in addition to OSI and IPv4. IS-IS in IPv6 supports either single-topology mode or multiple topology mode. IS-IS Single-Topology Support for IPv6Single-topology support for IPv6 allows IS-IS for IPv6 to be configured on interfaces along with other network protocols (for example, IPv4 and Connectionless Network Service [CLNS]). All interfaces must be configured with the identical set of network address families. In addition, all routers in the IS-IS area (for Level 1 routing) or the domain (for Level 2 routing) must support the identical set of network layer address families on all interfaces. When single-topology support for IPv6 is being used, either old- or new-style TLVs may be used. However, the TLVs used to advertise reachability to IPv6 prefixes use extended metrics. Cisco routers do not allow an interface metric to be set to a value greater than 63 if the configuration is not set to support only new-style TLVs for IPv4. In single-topology IPv6 mode, the configured metric is always the same for both IPv4 and IPv6. IPv6 IS-IS Local RIBA router that is running IS-IS IPv6 maintains a local RIB in which it stores all routes to destinations it has learned from its neighbors. At the end of each SPF, IS-IS attempts to install the best (that is, the least-cost) routes to a destination present in the local RIB in the global IPv6 routing table. How to Configure IPv6 Routing: IS-IS Support for IPv6
Configuring Single-Topology IS-IS for IPv6Perform this task to create an IPv6 IS-IS process and enable IPv6 IS-IS support on an interface. Configuring IS-IS comprises two activities. The first activity creates an IS-IS routing process and is performed using protocol-independent IS-IS commands. The second activity in configuring IPv6 IS-IS configures the operation of the IS-IS protocol on an interface. Before You Begin
SUMMARY STEPS
Before configuring the router to run IPv6 IS-IS, globally enable IPv6 using the ipv6 unicast-routing global configuration command. DETAILED STEPS Customizing IPv6 IS-ISPerform this task to configure a new administrative distance for IPv6 IS-IS, configure the maximum number of equal-cost paths that IPv6 IS-IS will support, configure summary prefixes for IPv6 IS-IS, and configure an IS-IS instance to advertise the default IPv6 route (::/0). It also explains how to configure the hold-down period between partial route calculations (PRCs) and how often Cisco IOS software performs the SPF calculation when using multitopology IS-IS. You can customize IS-IS multitopology for IPv6 for your network, but you likely will not need to do so. The defaults for this feature are set to meet the requirements of most customers and features. If you change the defaults, refer to the IPv4 configuration guide and the IPv6 command reference to find the appropriate syntax. DETAILED STEPS
Disabling IPv6 Protocol-Support Consistency ChecksPerform this task to disable protocol-support consistency checks in IPv6 single-topology mode. For single-topology IS-IS IPv6, routers must be configured to run the same set of address families. IS-IS performs consistency checks on hello packets and will reject hello packets that do not have the same set of configured address families. For example, a router running IS-IS for both IPv4 and IPv6 will not form an adjacency with a router running IS-IS for IPv4 or IPv6 only. In order to allow adjacency to be formed in mismatched address-families network, the adjacency-check command in IPv6 address family configuration mode must be disabled.
DETAILED STEPS
Disabling IPv4 Subnet Consistency ChecksPerform this task to disable IPv4 subnet consistency checking when forming adjacencies. Cisco IOS software historically makes checks on hello packets to ensure that the IPv4 address is present and has a consistent subnet with the neighbor from which the hello packets are received. To disable this check, use the no adjacency-check command in the router configuration mode. However, if multitopology IS-IS is configured, this check is automatically suppressed, because multitopology IS-IS requires routers to form an adjacency regardless of whether or not all routers on a LAN support a common protocol. DETAILED STEPS
Verifying IPv6 IS-IS Configuration and OperationSUMMARY STEPS
DETAILED STEPS
Configuration Examples for IPv6 Routing: IS-IS Support for IPv6
Example: Customizing IPv6 IS-ISThe following example advertises the IPv6 default route (::/0)--with an origin of Ethernet interface 0/0/1--with all other routes in router updates sent on Ethernet interface 0/0/1. This example also sets an administrative distance for IPv6 IS-IS to 90, defines the maximum number of equal-cost paths that IPv6 IS-IS will support as 3, and configures a summary prefix of 2001:DB8::/24 for IPv6 IS-IS. router isis address-family ipv6 default-information originate distance 90 maximum-paths 3 summary-prefix 2001:DB8::/24 exit Example: Configuring IS-IS for IPv6In the following example, output information about the parameters and current state of that active IPv6 routing processes is displayed using the show ipv6 protocolscommand:
Router# show ipv6 protocols
IPv6 Routing Protocol is "connected"
IPv6 Routing Protocol is "static"
IPv6 Routing Protocol is "isis"
Interfaces:
Ethernet0
Ethernet1
Serial1
Loopback1 (Passive)
Loopback2 (Passive)
Loopback3 (Passive)
Loopback4 (Passive)
Loopback5 (Passive)
Redistribution:
Redistributing protocol static at level 1
Address Summarization:
L2: 2001:DB8:33::/16 advertised with metric 0
L2: 2001:DB8:44::/16 advertised with metric 20
L2: 2001:DB8:66::/16 advertised with metric 10
L2: 2001:DB8:77::/16 advertised with metric 10
In the following example, output information about all connected routers running IS-IS in all areas is displayed using the show isis topologycommand:
Router# show isis topology
IS-IS paths to level-1 routers
System Id Metric Next-Hop Interface SNPA
0000.0000.000C
0000.0000.000D 20 0000.0000.00AA Se1/0/1 *HDLC*
0000.0000.000F 10 0000.0000.000F GE0/0/1 0050.e2e5.d01d
0000.0000.00AA 10 0000.0000.00AA Se1/0/1 *HDLC*
IS-IS paths to level-2 routers
System Id Metric Next-Hop Interface SNPA
0000.0000.000A 10 0000.0000.000A GE0/0/3 0010.f68d.f063
0000.0000.000B 20 0000.0000.000A GE0/0/3 0010.f68d.f063
0000.0000.000C --
0000.0000.000D 30 0000.0000.000A GE0/0/3 0010.f68d.f063
0000.0000.000E 30 0000.0000.000A GE0/0/3 0010.f68d.f063
In the following example, output information to confirm that the local router has formed all the necessary IS-IS adjacencies with other IS-IS neighbors is displayed using the show clns is-neighborscommand. To display the IPv6 link-local addresses of the neighbors, specify the detail keyword.
Router# show clns is-neighbors detail
System Id Interface State Type Priority Circuit Id Format
0000.0000.00AA Se1 Up L1 0 00 Phase V
Area Address(es): 49.0001
IPv6 Address(es): FE80::YYYY:D37C:C854:5
Uptime: 17:21:38
0000.0000.000F Et0 Up L1 64 0000.0000.000C.02 Phase V
Area Address(es): 49.0001
IPv6 Address(es): FE80::XXXX:E2FF:FEE5:D01D
Uptime: 17:21:41
0000.0000.000A Et0 Up L2 64 0000.0000.000C.01 Phase V
Area Address(es): 49.000b
IPv6 Address(es): FE80::ZZZZ:F6FF:FE8D:F063
Uptime: 17:22:06
In the following example, detailed output information about LSPs received from other routers and the IPv6 prefixes they are advertising is displayed using the show isis databasecommand with the detail keyword specified:
Router# show isis database detail
IS-IS Level-1 Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0C00.0C35.00-00 0x0000000C 0x5696 325 0/0/0
Area Address: 47.0004.004D.0001
Area Address: 39.0001
Metric: 10 IS 0000.0C00.62E6.03
Metric: 0 ES 0000.0C00.0C35
--More--
0000.0C00.40AF.00-00* 0x00000009 0x8452 608 1/0/0
Area Address: 47.0004.004D.0001
Topology: IPv4 (0x0) IPv6 (0x2)
NLPID: 0xCC 0x8E
IP Address: 172.16.21.49
Metric: 10 IS 0800.2B16.24EA.01
Metric: 10 IS 0000.0C00.62E6.03
Metric: 0 ES 0000.0C00.40AF
IPv6 Address: 2001:DB8::/32
Metric: 10 IPv6 (MT-IPv6) 2001:DB8::/64
Metric: 5 IS-Extended cisco.03
Metric: 10 IS-Extended cisco1.03
Metric: 10 IS (MT-IPv6) cisco.03
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0000.000A.00-00 0x00000059 0x378A 949 0/0/0
Area Address: 49.000b
NLPID: 0x8E
IPv6 Address: 2001:DB8:1:1:1:1:1:1
Metric: 10 IPv6 2001:DB8:2:YYYY::/64
Metric: 10 IPv6 2001:DB8:3:YYYY::/64
Metric: 10 IPv6 2001:DB8:2:YYYY::/64
Metric: 10 IS-Extended 0000.0000.000A.01
Metric: 10 IS-Extended 0000.0000.000B.00
Metric: 10 IS-Extended 0000.0000.000C.01
Metric: 0 IPv6 11:1:YYYY:1:1:1:1:1/128
Metric: 0 IPv6 11:2:YYYY:1:1:1:1:1/128
Metric: 0 IPv6 11:3:YYYY:1:1:1:1:1/128
Metric: 0 IPv6 11:4:YYYY:1:1:1:1:1/128
Metric: 0 IPv6 11:5:YYYY:1:1:1:1:1/128
0000.0000.000A.01-00 0x00000050 0xB0AF 491 0/0/0
Metric: 0 IS-Extended 0000.0000.000A.00
Metric: 0 IS-Extended 0000.0000.000B.00
The following example shows output from the show isis ipv6 rib command. An asterisk (*) indicates prefixes that have been installed in the master IPv6 RIB as IS-IS routes. Following each prefix is a list of all paths in order of preference, with optimal paths listed first and suboptimal paths listed after optimal paths.
Router# show isis ipv6 rib
IS-IS IPv6 process "", local RIB
2001:DB8:88:1::/64
via FE80::210:7BFF:FEC2:ACC9/GigabitEthernet2/0/0, type L2 metric 20 LSP [3/7]
via FE80::210:7BFF:FEC2:ACCC/GigabitEthernet2/1/0, type L2 metric 20 LSP [3/7]
* 2001:DB8:1357:1::/64
via FE80::202:7DFF:FE1A:9471/GigabitEthernet2/1/0, type L2 metric 10 LSP [4/9]
* 2001:DB8:45A::/64
via FE80::210:7BFF:FEC2:ACC9/GigabitEthernet2/0/0, type L1 metric 20 LSP [C/6]
via FE80::210:7BFF:FEC2:ACCC/GigabitEthernet2/1/0, type L1 metric 20 LSP [C/6]
via FE80::210:7BFF:FEC2:ACC9/GigabitEthernet2/0/0, type L2 metric 20 LSP [3/7]
via FE80::210:7BFF:FEC2:ACCC/GigabitEthernet2/1/0, type L2 metric 20 LSP [3/7]
Additional ReferencesRelated Documents
MIBsTechnical Assistance
Feature Information for IPv6 Routing: IS-IS Support for IPv6The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature. Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R) Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental. © 2012 Cisco Systems, Inc. All rights reserved.
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