Contents

IPv6 Routing: IS-IS Support for IPv6

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 Information

Your 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.

Information About IPv6 Routing: IS-IS Support for IPv6

IS-IS Enhancements for IPv6

IS-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 IPv6

Single-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 RIB

A 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 IPv6

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

Before configuring the router to run IPv6 IS-IS, globally enable IPv6 using the ipv6 unicast-routing global configuration command.


Note

If you are using IS-IS single-topology support for IPv6, IPv4, or both IPv6 and IPv4, you may configure both IPv6 and IPv4 on an IS-IS interface for Level 1, Level 2, or both Level 1 and Level 2. However, if both IPv6 and IPv4 are configured on the same interface, they must be running the same IS-IS level. That is, IPv4 cannot be configured to run on IS-IS Level 1 only on a specified GigabitEthernet or FastEthernet interface while IPv6 is configured to run IS-IS Level 2 only on the same GigabitEthernet or FastEthernet interface.

>
SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    router isis area-tag

    4.    net network-entity-title

    5.    exit

    6.    interface type number

    7.    ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length

    8.    ipv6 router isis area-name


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 router isis area-tag


    Example:
    Router(config)# router isis area2
     

    Enables IS-IS for the specified IS-IS routing process, and enters router configuration mode.

     
    Step 4 net network-entity-title


    Example:
    Router(config-router)# net 49.0001.0000.0000.000c.00
     

    Configures an IS-IS network entity title (NET) for the routing process.

    • The network-entity-title argument defines the area addresses for the IS-IS area and the system ID of the router.

     
    Step 5 exit


    Example:
    Router(config-router)# exit
     

    Exits router configuration mode and enters global configuration mode.

     
    Step 6 interface type number


    Example:
    Router(config)# interface GigabitEthernet 0/0/1
     

    Specifies the interface type and number, and enters interface configuration mode.

     
    Step 7 ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length


    Example:
    Router(config-if)# ipv6 address 2001:DB8::3/64
     

    Specifies the IPv6 network assigned to the interface and enables IPv6 processing on the interface.

    Note   

    Refer to the Implementing IPv6 Addressing and Basic Connectivity module for more information on configuring IPv6 addresses.

     
    Step 8 ipv6 router isis area-name


    Example:
    Router(config-if)# ipv6 router isis area2
     

    Enables the specified IPv6 IS-IS routing process on an interface.

     

    Customizing IPv6 IS-IS

    Perform 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 XE 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.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    router isis area-tag

      4.    address-family ipv6 [unicast | multicast]

      5.    default-information originate [route-map map-name]

      6.    distance value

      7.    maximum-paths number-paths

      8.    summary-prefix ipv6-prefix prefix-length level-1 | level-1-2| level-2]

      9.    prc-interval seconds [initial-wait] [secondary-wait

      10.    spf-interval [level-1 | level-2] seconds initial-wait] [secondary-wait

      11.    exit

      12.    interface type number

      13.    isis ipv6 metric metric-value [level-1 | level-2 | level-1-2


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 router isis area-tag


      Example:
      Router(config)# router isis area2
       

      Enables IS-IS for the specified IS-IS routing process, and enters router configuration mode.

       
      Step 4 address-family ipv6 [unicast | multicast]


      Example:
      Router(config-router)# address-family ipv6
       

      Specifies the IPv6 address family, and enters address family configuration mode.

      • The unicast keyword specifies the unicast IPv6 unicast address family. By default, the router is placed in configuration mode for the unicast IPv6 address family if the unicast keyword is not specified with the address-family ipv6 command.

       
      Step 5 default-information originate [route-map map-name]


      Example:
      Router(config-router-af)# default-information originate
       

      (Optional) Injects a default IPv6 route into an IS-IS routing domain.

      • The route-map keyword and map-name argument specify the conditions under which the IPv6 default route is advertised.

      • If the route map keyword is omitted, then the IPv6 default route will be unconditionally advertised at Level 2.

       
      Step 6 distance value


      Example:
      Router(config-router-af)# distance 90
       

      (Optional) Defines an administrative distance for IPv6 IS-IS routes in the IPv6 routing table.

      • The valueargument is an integer from 10 to 254. (The values 0 to 9 are reserved for internal use).

       
      Step 7 maximum-paths number-paths


      Example:
      Router(config-router-af)# maximum-paths 3
       

      (Optional) Defines the maximum number of equal-cost routes that IPv6 IS-IS can support.

      • This command also supports IPv6 Border Gateway Protocol (BGP) and Routing Information Protocol (RIP).

      • The number-paths argument is an integer from 1 to 64. The default for BGP is one path; the default for IS-IS and RIP is 16 paths.

       
      Step 8 summary-prefix ipv6-prefix prefix-length level-1 | level-1-2| level-2]


      Example:
      Router(config-router-af)# summary-prefix 2001:DB8::/24
       

      (Optional) Allows a Level 1-2 router to summarize Level 1 prefixes at Level 2, instead of advertising the Level 1 prefixes directly when the router advertises the summary.

      • The ipv6-prefix argument in the summary-prefix 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 argument 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.

       
      Step 9 prc-interval seconds [initial-wait] [secondary-wait


      Example:
      Router(config-router-af)# prc-interval 20
       

      (Optional) Configures the hold-down period between PRCs for multitopology IS-IS for IPv6.

       
      Step 10 spf-interval [level-1 | level-2] seconds initial-wait] [secondary-wait


      Example:
      Router(config-router-af)# spf-interval 30
       

      (Optional) Configures how often Cisco IOS XE software performs the SPF calculation for multitopology IS-IS for IPv6.

       
      Step 11 exit


      Example:
      Router(config-router-af)# exit
       

      Exits address family configuration mode, and returns the router to router configuration mode.

      • Repeat this step to exit router configuration mode and return the router to global configuration mode.

       
      Step 12 interface type number


      Example:
      Router(config-router)# interface GigabitEthernet 0/0/1
       

      Specifies the interface type and number, and enters interface configuration mode.

       
      Step 13 isis ipv6 metric metric-value [level-1 | level-2 | level-1-2


      Example:
      Router(config-if)# isis ipv6 metric 20
       

      (Optional) Configures the value of an multitopology IS-IS for IPv6 metric.

       

      Disabling IPv6 Protocol-Support Consistency Checks

      Perform 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.


      Note

      Entering the no adjacency-check command can adversely affect your network configuration. Enter the no adjacency-check command only when you are running IPv4 IS-IS on all your routers and you want to add IPv6 IS-IS to your network but you need to maintain all your adjacencies during the transition. When the IPv6 IS-IS configuration is complete, remove the no adjacency-checkcommand from the configuration.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    router isis area-tag

        4.    address-family ipv6 [unicast | multicast]

        5.    no adjacency-check


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2 configure terminal


        Example:
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 router isis area-tag


        Example:
        Router(config)# router isis area2
         

        Enables IS-IS for the specified IS-IS routing process, and enters router configuration mode.

         
        Step 4 address-family ipv6 [unicast | multicast]


        Example:
        Router(config-router)# address-family ipv6
         

        Specifies the IPv6 address family, and enters address family configuration mode.

        • The unicast keyword specifies the unicast IPv6 unicast address family. By default, the router is placed in configuration mode for the unicast IPv6 address family if the unicast keyword is not specified with the address-family ipv6 command.

         
        Step 5 no adjacency-check


        Example:
        Router(config-router-af)# no adjacency-check
         

        Disables the IPv6 protocol-support consistency checks performed on hello packets, allowing IPv6 to be introduced into an IPv4-only network without disrupting existing adjacencies.

        • The adjacency-checkcommand is enabled by default.

         

        Disabling IPv4 Subnet Consistency Checks

        Perform this task to disable IPv4 subnet consistency checking when forming adjacencies. 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.

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    router isis area-tag

          4.    no adjacency-check


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Router> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2 configure terminal


          Example:
          Router# configure terminal
           

          Enters global configuration mode.

           
          Step 3 router isis area-tag


          Example:
          Router(config)# router isis area2
           

          Enables IS-IS for the specified IS-IS routing process, and enters router configuration mode.

           
          Step 4 no adjacency-check


          Example:
          Router(config-router-af)# no adjacency-check
           

          Disables the IPv6 protocol-support consistency checks performed on hello packets, allowing IPv6 to be introduced into an IPv4-only network without disrupting existing adjacencies.

          • The adjacency-checkcommand is enabled by default.

           

          Verifying IPv6 IS-IS Configuration and Operation

          SUMMARY STEPS

            1.    enable

            2.    show ipv6 protocols [summary]

            3.    show isis [process-tag] [ipv6 | *] topology

            4.    show clns [process-tag] neighbors interface-type interface-number] [area] [detail]

            5.    show clns area-tag is-neighbors [type number] [detail]

            6.    show isis [process-tag] database [level-1] [level-2] [l1] [l2] [detail] [lspid]

            7.    show isis ipv6 rib [ipv6-prefix]


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example:
            Device> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.

             
            Step 2 show ipv6 protocols [summary]


            Example:
            Device# show ipv6 protocols
             

            Displays the parameters and current state of the active IPv6 routing processes.

             
            Step 3 show isis [process-tag] [ipv6 | *] topology


            Example:
            Device# show isis topology
             

            Displays a list of all connected routers running IS-IS in all areas.

             
            Step 4 show clns [process-tag] neighbors interface-type interface-number] [area] [detail]


            Example:
            Device# show clns neighbors detail
             

            Displays end system (ES), intermediate system (IS), and multitopology IS-IS (M-ISIS) neighbors.

             
            Step 5 show clns area-tag is-neighbors [type number] [detail]


            Example:
            Device# show clns is-neighbors detail
             

            Displays IS-IS adjacency information for IS-IS neighbors.

            • Use the detail keyword to display the IPv6 link-local addresses of the neighbors.

             
            Step 6 show isis [process-tag] database [level-1] [level-2] [l1] [l2] [detail] [lspid]


            Example:
            Device# show isis database detail
             

            Displays the IS-IS link-state database.

            • In this example, the contents of each LSP are displayed using the detail keyword.

             
            Step 7 show isis ipv6 rib [ipv6-prefix]


            Example:
            Device# show isis ipv6 rib
             

            Displays the IPv6 local RIB.

             

            Configuration Examples for IPv6 Routing: IS-IS Support for IPv6

            Example: Customizing IPv6 IS-IS

            The following example advertises the IPv6 default route (::/0)--with an origin of GigabitEthernet interface 0/0/1--with all other routes in router updates sent on GigabitEthernet 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: Disabling IPv6 Protocol-Support Consistency Checks

            The following example disables the adjacency-check command to allow a network administrator to configure IPv6 IS-IS on the router without disrupting the existing adjacencies: 

            router isis 
 address-family ipv6
 no adjacency-check

            Example: Configuring IS-IS for IPv6

            In 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:
    GigabitEthernet0/0/3
    GigabitEthernet0/0/1
    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

            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 Se1/0/1     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

            In 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     GE3/3        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     GE3/2        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     GE3/3        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     GE3/2        aa00.0400.9205  Up     8         L1   IS-IS
Area Address(es): 20
IP Address(es): 192.168.0.30*
Uptime: 00:21:52

            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 References

            Related Documents

            Related Topic

            Document Title

            IS-IS commands: complete command syntax, command mode, defaults, command history, usage guidelines, and examples

            Cisco IOS IP Routing: ISIS Command Reference

            Overview of Cisco IS-IS conceptual information with links to all the individual IS-IS modules

            "Integrated IS-IS Routing Protocol Overview"

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            RFCs

            RFC

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            Description

            Link

            The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

            http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

            Feature Information for IPv6 Routing: IS-IS Support for IPv6

            The 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.

            Table 1 Feature Information for IPv6 Routing: IS-IS Support for IPv6

            Feature Name

            Releases

            Feature Information

            IPv6 Routing: IS-IS Support for IPv6

            Cisco IOS XE Release 2.4

            IPv6 enhancements to IS-IS allow IS-IS to advertise IPv6 prefixes in addition to IPv4 and OSI routes.

            The following commands were introduced or modified: address-family ipv6 (IS-IS), adjacency-check, default-information originate (IPv6 IS-IS), distance (IPv6), ipv6 router isis , isis ipv6 metric, maximum-paths (IPv6), prc-interval (IPv6), router isis , show clns neighbors, show ipv6 protocols, show isis database, show isis topology, spf-interval, summary-prefix (IPv6 IS-IS).

            IPv6 ISIS Local RIB

            Cisco IOS XE Release 2.6

            A 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.

            The following command was introduced: show isis ipv6 rib.

            IPv6 Routing: IS-IS Support for IPv6

            IPv6 Routing: IS-IS Support for IPv6

            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 Information

            Your 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.

            Information About IPv6 Routing: IS-IS Support for IPv6

            IS-IS Enhancements for IPv6

            IS-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 IPv6

            Single-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 RIB

            A 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 IPv6

            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

            Before configuring the router to run IPv6 IS-IS, globally enable IPv6 using the ipv6 unicast-routing global configuration command.


            Note

            If you are using IS-IS single-topology support for IPv6, IPv4, or both IPv6 and IPv4, you may configure both IPv6 and IPv4 on an IS-IS interface for Level 1, Level 2, or both Level 1 and Level 2. However, if both IPv6 and IPv4 are configured on the same interface, they must be running the same IS-IS level. That is, IPv4 cannot be configured to run on IS-IS Level 1 only on a specified GigabitEthernet or FastEthernet interface while IPv6 is configured to run IS-IS Level 2 only on the same GigabitEthernet or FastEthernet interface.

            >
            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    router isis area-tag

              4.    net network-entity-title

              5.    exit

              6.    interface type number

              7.    ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length

              8.    ipv6 router isis area-name


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example:
              Router> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.

               
              Step 2 configure terminal


              Example:
              Router# configure terminal
               

              Enters global configuration mode.

               
              Step 3 router isis area-tag


              Example:
              Router(config)# router isis area2
               

              Enables IS-IS for the specified IS-IS routing process, and enters router configuration mode.

               
              Step 4 net network-entity-title


              Example:
              Router(config-router)# net 49.0001.0000.0000.000c.00
               

              Configures an IS-IS network entity title (NET) for the routing process.

              • The network-entity-title argument defines the area addresses for the IS-IS area and the system ID of the router.

               
              Step 5 exit


              Example:
              Router(config-router)# exit
               

              Exits router configuration mode and enters global configuration mode.

               
              Step 6 interface type number


              Example:
              Router(config)# interface GigabitEthernet 0/0/1
               

              Specifies the interface type and number, and enters interface configuration mode.

               
              Step 7 ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length


              Example:
              Router(config-if)# ipv6 address 2001:DB8::3/64
               

              Specifies the IPv6 network assigned to the interface and enables IPv6 processing on the interface.

              Note   

              Refer to the Implementing IPv6 Addressing and Basic Connectivity module for more information on configuring IPv6 addresses.

               
              Step 8 ipv6 router isis area-name


              Example:
              Router(config-if)# ipv6 router isis area2
               

              Enables the specified IPv6 IS-IS routing process on an interface.

               

              Customizing IPv6 IS-IS

              Perform 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 XE 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.

              SUMMARY STEPS

                1.    enable

                2.    configure terminal

                3.    router isis area-tag

                4.    address-family ipv6 [unicast | multicast]

                5.    default-information originate [route-map map-name]

                6.    distance value

                7.    maximum-paths number-paths

                8.    summary-prefix ipv6-prefix prefix-length level-1 | level-1-2| level-2]

                9.    prc-interval seconds [initial-wait] [secondary-wait

                10.    spf-interval [level-1 | level-2] seconds initial-wait] [secondary-wait

                11.    exit

                12.    interface type number

                13.    isis ipv6 metric metric-value [level-1 | level-2 | level-1-2


              DETAILED STEPS
                 Command or ActionPurpose
                Step 1 enable


                Example:
                Router> enable
                 

                Enables privileged EXEC mode.

                • Enter your password if prompted.

                 
                Step 2 configure terminal


                Example:
                Router# configure terminal
                 

                Enters global configuration mode.

                 
                Step 3 router isis area-tag


                Example:
                Router(config)# router isis area2
                 

                Enables IS-IS for the specified IS-IS routing process, and enters router configuration mode.

                 
                Step 4 address-family ipv6 [unicast | multicast]


                Example:
                Router(config-router)# address-family ipv6
                 

                Specifies the IPv6 address family, and enters address family configuration mode.

                • The unicast keyword specifies the unicast IPv6 unicast address family. By default, the router is placed in configuration mode for the unicast IPv6 address family if the unicast keyword is not specified with the address-family ipv6 command.

                 
                Step 5 default-information originate [route-map map-name]


                Example:
                Router(config-router-af)# default-information originate
                 

                (Optional) Injects a default IPv6 route into an IS-IS routing domain.

                • The route-map keyword and map-name argument specify the conditions under which the IPv6 default route is advertised.

                • If the route map keyword is omitted, then the IPv6 default route will be unconditionally advertised at Level 2.

                 
                Step 6 distance value


                Example:
                Router(config-router-af)# distance 90
                 

                (Optional) Defines an administrative distance for IPv6 IS-IS routes in the IPv6 routing table.

                • The valueargument is an integer from 10 to 254. (The values 0 to 9 are reserved for internal use).

                 
                Step 7 maximum-paths number-paths


                Example:
                Router(config-router-af)# maximum-paths 3
                 

                (Optional) Defines the maximum number of equal-cost routes that IPv6 IS-IS can support.

                • This command also supports IPv6 Border Gateway Protocol (BGP) and Routing Information Protocol (RIP).

                • The number-paths argument is an integer from 1 to 64. The default for BGP is one path; the default for IS-IS and RIP is 16 paths.

                 
                Step 8 summary-prefix ipv6-prefix prefix-length level-1 | level-1-2| level-2]


                Example:
                Router(config-router-af)# summary-prefix 2001:DB8::/24
                 

                (Optional) Allows a Level 1-2 router to summarize Level 1 prefixes at Level 2, instead of advertising the Level 1 prefixes directly when the router advertises the summary.

                • The ipv6-prefix argument in the summary-prefix 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 argument 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.

                 
                Step 9 prc-interval seconds [initial-wait] [secondary-wait


                Example:
                Router(config-router-af)# prc-interval 20
                 

                (Optional) Configures the hold-down period between PRCs for multitopology IS-IS for IPv6.

                 
                Step 10 spf-interval [level-1 | level-2] seconds initial-wait] [secondary-wait


                Example:
                Router(config-router-af)# spf-interval 30
                 

                (Optional) Configures how often Cisco IOS XE software performs the SPF calculation for multitopology IS-IS for IPv6.

                 
                Step 11 exit


                Example:
                Router(config-router-af)# exit
                 

                Exits address family configuration mode, and returns the router to router configuration mode.

                • Repeat this step to exit router configuration mode and return the router to global configuration mode.

                 
                Step 12 interface type number


                Example:
                Router(config-router)# interface GigabitEthernet 0/0/1
                 

                Specifies the interface type and number, and enters interface configuration mode.

                 
                Step 13 isis ipv6 metric metric-value [level-1 | level-2 | level-1-2


                Example:
                Router(config-if)# isis ipv6 metric 20
                 

                (Optional) Configures the value of an multitopology IS-IS for IPv6 metric.

                 

                Disabling IPv6 Protocol-Support Consistency Checks

                Perform 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.


                Note

                Entering the no adjacency-check command can adversely affect your network configuration. Enter the no adjacency-check command only when you are running IPv4 IS-IS on all your routers and you want to add IPv6 IS-IS to your network but you need to maintain all your adjacencies during the transition. When the IPv6 IS-IS configuration is complete, remove the no adjacency-checkcommand from the configuration.

                SUMMARY STEPS

                  1.    enable

                  2.    configure terminal

                  3.    router isis area-tag

                  4.    address-family ipv6 [unicast | multicast]

                  5.    no adjacency-check


                DETAILED STEPS
                   Command or ActionPurpose
                  Step 1 enable


                  Example:
                  Router> enable
                   

                  Enables privileged EXEC mode.

                  • Enter your password if prompted.

                   
                  Step 2 configure terminal


                  Example:
                  Router# configure terminal
                   

                  Enters global configuration mode.

                   
                  Step 3 router isis area-tag


                  Example:
                  Router(config)# router isis area2
                   

                  Enables IS-IS for the specified IS-IS routing process, and enters router configuration mode.

                   
                  Step 4 address-family ipv6 [unicast | multicast]


                  Example:
                  Router(config-router)# address-family ipv6
                   

                  Specifies the IPv6 address family, and enters address family configuration mode.

                  • The unicast keyword specifies the unicast IPv6 unicast address family. By default, the router is placed in configuration mode for the unicast IPv6 address family if the unicast keyword is not specified with the address-family ipv6 command.

                   
                  Step 5 no adjacency-check


                  Example:
                  Router(config-router-af)# no adjacency-check
                   

                  Disables the IPv6 protocol-support consistency checks performed on hello packets, allowing IPv6 to be introduced into an IPv4-only network without disrupting existing adjacencies.

                  • The adjacency-checkcommand is enabled by default.

                   

                  Disabling IPv4 Subnet Consistency Checks

                  Perform this task to disable IPv4 subnet consistency checking when forming adjacencies. 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.

                  SUMMARY STEPS

                    1.    enable

                    2.    configure terminal

                    3.    router isis area-tag

                    4.    no adjacency-check


                  DETAILED STEPS
                     Command or ActionPurpose
                    Step 1 enable


                    Example:
                    Router> enable
                     

                    Enables privileged EXEC mode.

                    • Enter your password if prompted.

                     
                    Step 2 configure terminal


                    Example:
                    Router# configure terminal
                     

                    Enters global configuration mode.

                     
                    Step 3 router isis area-tag


                    Example:
                    Router(config)# router isis area2
                     

                    Enables IS-IS for the specified IS-IS routing process, and enters router configuration mode.

                     
                    Step 4 no adjacency-check


                    Example:
                    Router(config-router-af)# no adjacency-check
                     

                    Disables the IPv6 protocol-support consistency checks performed on hello packets, allowing IPv6 to be introduced into an IPv4-only network without disrupting existing adjacencies.

                    • The adjacency-checkcommand is enabled by default.

                     

                    Verifying IPv6 IS-IS Configuration and Operation

                    SUMMARY STEPS

                      1.    enable

                      2.    show ipv6 protocols [summary]

                      3.    show isis [process-tag] [ipv6 | *] topology

                      4.    show clns [process-tag] neighbors interface-type interface-number] [area] [detail]

                      5.    show clns area-tag is-neighbors [type number] [detail]

                      6.    show isis [process-tag] database [level-1] [level-2] [l1] [l2] [detail] [lspid]

                      7.    show isis ipv6 rib [ipv6-prefix]


                    DETAILED STEPS
                       Command or ActionPurpose
                      Step 1 enable


                      Example:
                      Device> enable
                       

                      Enables privileged EXEC mode.

                      • Enter your password if prompted.

                       
                      Step 2 show ipv6 protocols [summary]


                      Example:
                      Device# show ipv6 protocols
                       

                      Displays the parameters and current state of the active IPv6 routing processes.

                       
                      Step 3 show isis [process-tag] [ipv6 | *] topology


                      Example:
                      Device# show isis topology
                       

                      Displays a list of all connected routers running IS-IS in all areas.

                       
                      Step 4 show clns [process-tag] neighbors interface-type interface-number] [area] [detail]


                      Example:
                      Device# show clns neighbors detail
                       

                      Displays end system (ES), intermediate system (IS), and multitopology IS-IS (M-ISIS) neighbors.

                       
                      Step 5 show clns area-tag is-neighbors [type number] [detail]


                      Example:
                      Device# show clns is-neighbors detail
                       

                      Displays IS-IS adjacency information for IS-IS neighbors.

                      • Use the detail keyword to display the IPv6 link-local addresses of the neighbors.

                       
                      Step 6 show isis [process-tag] database [level-1] [level-2] [l1] [l2] [detail] [lspid]


                      Example:
                      Device# show isis database detail
                       

                      Displays the IS-IS link-state database.

                      • In this example, the contents of each LSP are displayed using the detail keyword.

                       
                      Step 7 show isis ipv6 rib [ipv6-prefix]


                      Example:
                      Device# show isis ipv6 rib
                       

                      Displays the IPv6 local RIB.

                       

                      Configuration Examples for IPv6 Routing: IS-IS Support for IPv6

                      Example: Customizing IPv6 IS-IS

                      The following example advertises the IPv6 default route (::/0)--with an origin of GigabitEthernet interface 0/0/1--with all other routes in router updates sent on GigabitEthernet 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: Disabling IPv6 Protocol-Support Consistency Checks

                      The following example disables the adjacency-check command to allow a network administrator to configure IPv6 IS-IS on the router without disrupting the existing adjacencies: 

                      router isis 
 address-family ipv6
 no adjacency-check

                      Example: Configuring IS-IS for IPv6

                      In 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:
    GigabitEthernet0/0/3
    GigabitEthernet0/0/1
    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

                      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 Se1/0/1     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

                      In 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     GE3/3        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     GE3/2        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     GE3/3        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     GE3/2        aa00.0400.9205  Up     8         L1   IS-IS
Area Address(es): 20
IP Address(es): 192.168.0.30*
Uptime: 00:21:52

                      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 References

                      Related Documents

                      Related Topic

                      Document Title

                      IS-IS commands: complete command syntax, command mode, defaults, command history, usage guidelines, and examples

                      Cisco IOS IP Routing: ISIS Command Reference

                      Overview of Cisco IS-IS conceptual information with links to all the individual IS-IS modules

                      "Integrated IS-IS Routing Protocol Overview"

                      Standards

                      Standard

                      Title

                      No new or modified standards are supported, and support for existing standards has not been modified.

                      --

                      RFCs

                      RFC

                      Title

                      No new or modified RFCs are supported, and support for existing RFCs has not been modified.

                      --

                      Technical Assistance

                      Description

                      Link

                      The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

                      http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

                      Feature Information for IPv6 Routing: IS-IS Support for IPv6

                      The 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.

                      Table 1 Feature Information for IPv6 Routing: IS-IS Support for IPv6

                      Feature Name

                      Releases

                      Feature Information

                      IPv6 Routing: IS-IS Support for IPv6

                      Cisco IOS XE Release 2.4

                      IPv6 enhancements to IS-IS allow IS-IS to advertise IPv6 prefixes in addition to IPv4 and OSI routes.

                      The following commands were introduced or modified: address-family ipv6 (IS-IS), adjacency-check, default-information originate (IPv6 IS-IS), distance (IPv6), ipv6 router isis , isis ipv6 metric, maximum-paths (IPv6), prc-interval (IPv6), router isis , show clns neighbors, show ipv6 protocols, show isis database, show isis topology, spf-interval, summary-prefix (IPv6 IS-IS).

                      IPv6 ISIS Local RIB

                      Cisco IOS XE Release 2.6

                      A 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.

                      The following command was introduced: show isis ipv6 rib.