Implementing IS-IS for IPv6
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Contents
Implementing IS-IS for IPv6Last Updated: June 21, 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 caveats and feature information, see Bug Search Tool and 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 module. 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. Restrictions for Implementing IS-IS for IPv6In Cisco IOS Release 12.0(22)S or later releases, and Cisco IOS Release 12.2(8)T or later releases, IS-IS support for IPv6 implements single-topology IPv6 IS-IS functionality based on IETF IS-IS WG draft-ietf-isis-ipv6.txt. A single shortest path first (SPF) per level is used to compute OSI, IPv4 (if configured), and IPv6 routes. The use of a single SPF means that both IPv4 IS-IS and IPv6 IS-IS routing protocols must share a common network topology. To use IS-IS for IPv4 and IPv6 routing, any interface configured for IPv4 IS-IS must also be configured for IPv6 IS-IS, and vice versa. All routers within an IS-IS area (Level 1 routing) or domain (Level 2 routing) must also support the same set of address families: IPv4 only, IPv6 only, or both IPv4 and IPv6. Beginning with release Cisco IOS Release 12.2(15)T, IS-IS support for IPv6 is enhanced to also support multitopology IPv6 support as defined in IETF IS-IS WG draft-ietf-isis-wg-multi-topology.txt. Multitopology IPv6 IS-IS support uses multiple SPFs to compute routes and removes the restriction that all interfaces must support all configured address families and that all routers in an IS-IS area or domain must support the same set of address families. The following IS-IS router configuration commands are specific to IPv4 and are not supported by, or have any effect on, IPv6 IS-IS: ⢠mpls ⢠traffic-share Information About Implementing IS-IS 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. IS-IS Multitopology Support for IPv6IS-IS multitopology support for IPv6 allows IS-IS to maintain a set of independent topologies within a single area or domain. This mode removes the restriction that all interfaces on which IS-IS is configured must support the identical set of network address families. It also removes the restriction that all routers in the IS-IS area (for Level 1 routing) or domain (for Level 2 routing) must support the identical set of network layer address families. Because multiple SPFs are performed, one for each configured topology, it is sufficient that connectivity exists among a subset of the routers in the area or domain for a given network address family to be routable. You can use the isis ipv6 metric command to configure different metrics on an interface for IPv6 and IPv4. When multitopology support for IPv6 is used, use the metric-style widecommand to configure IS-IS to use new-style TLVs because TLVs used to advertise IPv6 information in link-state packets (LSPs) are defined to use only extended metrics. Transition from Single-Topology to Multitopology Support for IPv6All routers in the area or domain must use the same type of IPv6 support, either single-topology or multitopology. A router operating in multitopology mode will not recognize the ability of the single-topology mode router to support IPv6 traffic, which will lead to holes in the IPv6 topology. To transition from single-topology support to the more flexible multitopology support, a multitopology transition mode is provided. The multitopology transition mode allows a network operating in single-topology IS-IS IPv6 support mode to continue to work while upgrading routers to include multitopology IS-IS IPv6 support. While in transition mode, both types of TLVs (single-topology and multitopology) are sent in LSPs for all configured IPv6 addresses, but the router continues to operate in single-topology mode (that is, the topological restrictions of the single-topology mode are still in effect). After all routers in the area or domain have been upgraded to support multitopology IPv6 and are operating in transition mode, transition mode can be removed from the configuration. Once all routers in the area or domain are operating in multitopology IPv6 mode, the topological restrictions of single-topology mode are no longer in effect. 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. For further information on the IPv6 IS-IS local RIB, see the Verifying IPv6 IS-IS Configuration and Operation section. How to Implement IS-IS for IPv6When configuring supported routing protocols in IPv6, you must create the routing process, enable the routing process on interfaces, and customize the routing protocol for your particular network.
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 Configuring Multitopology IS-IS for IPv6When multitopology IS-IS for IPv6 is configured, the transition keyword allows a user who is working with the single-topology SPF mode of IS-IS IPv6 to continue to work while upgrading to multitopology IS-IS. After every router is configured with the transition keyword, users can remove the transition keyword on each router. When transition mode is not enabled, IPv6 connectivity between routers operating in single-topology mode and routers operating in multitopology mode is not possible. You can continue to use the existing IPv6 topology while upgrading to multitopology IS-IS. The optional isis ipv6 metric command allows you to differentiate between link costs for IPv6 and IPv4 traffic when operating in multitopology mode. 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
Redistributing Routes into an IPv6 IS-IS Routing ProcessSUMMARY STEPS
DETAILED STEPS
Redistributing IPv6 IS-IS Routes Between IS-IS Levels
SUMMARY STEPS
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
ExamplesSample Output from the show ipv6 protocols CommandIn 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:
Ethernet0/0/3
Ethernet0/0/1
Serial1/0/1
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
Sample Output from the show isis topology CommandIn 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 Et0/0/1 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 Et0/0/3 0010.f68d.f063
0000.0000.000B 20 0000.0000.000A Et0/0/3 0010.f68d.f063
0000.0000.000C --
0000.0000.000D 30 0000.0000.000A Et0/0/3 0010.f68d.f063
0000.0000.000E 30 0000.0000.000A Et0/0/3 0010.f68d.f063
Sample Output from the show clns is-neighbors CommandIn 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 Se1/0/1 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 Et0/0/1 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 Et0/0/3 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
Sample Output from the show clns neighbors CommandIn the following example, detailed output information that displays both end system (ES) and intermediate system (IS) neighbors is displayed using the show clns neighbors command with the detail keyword.
Router# show clns neighbors detail
System Id Interface SNPA State Holdtime Type Protocol
0000.0000.0007 Et3/3 aa00.0400.6408 UP 26 L1 IS-IS
Area Address(es): 20
IP Address(es): 172.16.0.42*
Uptime: 00:21:49
0000.0C00.0C35 Et3/2 0000.0c00.0c36 Up 91 L1 IS-IS
Area Address(es): 20
IP Address(es): 192.168.0.42*
Uptime: 00:21:52
0800.2B16.24EA Et3/3 aa00.0400.2d05 Up 27 L1 M-ISIS
Area Address(es): 20
IP Address(es): 192.168.0.42*
IPv6 Address(es): FE80::2B0:8EFF:FE31:EC57
Uptime: 00:00:27
0800.2B14.060E Et3/2 aa00.0400.9205 Up 8 L1 IS-IS
Area Address(es): 20
IP Address(es): 192.168.0.30*
Uptime: 00:21:52
Sample Output from the show isis database CommandIn 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
Sample Output from the show isis ipv6 rib CommandThe 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/Ethernet2/0, type L2 metric 20 LSP [3/7]
via FE80::210:7BFF:FEC2:ACCC/Ethernet2/1, type L2 metric 20 LSP [3/7]
* 2001:DB8:1357:1::/64
via FE80::202:7DFF:FE1A:9471/Ethernet2/1, type L2 metric 10 LSP [4/9]
* 2001:DB8:45A::/64
via FE80::210:7BFF:FEC2:ACC9/Ethernet2/0, type L1 metric 20 LSP [C/6]
via FE80::210:7BFF:FEC2:ACCC/Ethernet2/1, type L1 metric 20 LSP [C/6]
via FE80::210:7BFF:FEC2:ACC9/Ethernet2/0, type L2 metric 20 LSP [3/7]
via FE80::210:7BFF:FEC2:ACCC/Ethernet2/1, type L2 metric 20 LSP [3/7]
Configuration Examples for IPv6 IS-IS
Example Configuring Single-Topology IS-IS for IPv6The following example enables single-topology mode, creates an IS-IS process, defines the NET, configures an IPv6 address on an interface, and configures the interface to run IPv6 IS-IS: ipv6 unicast-routing ! router isis net 49.0001.0000.0000.000c.00 exit interface Ethernet0/0/1 ipv6 address 2001:DB8::3/64 ipv6 router isis area2 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 Additional ReferencesRelated Documents
MIBsTechnical Assistance
Feature Information for Implementing IS-IS 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 or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: 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. (1110R) 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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