Segment Routing—IS-IS v4 node SID

The Segment Routing—ISIS v4 node SID feature provides support for segment routing on Cisco Intermediate System-to-Intermediate System (IS-IS) networks.

Information About Segment Routing IS-IS v4 Node

Segment Routing IS-IS v4 node SID

Segment Routing (SR) is a technique by which the path followed by a packet is encoded in the packet itself. The path followed by a packet in segment routing is encoded in the packet itself similar to loose or strict source routing. Segment Routing relies on a small number of extensions to Cisco Intermediate System-to-Intermediate System (IS-IS) and Open Shortest Path First (OSPF) protocols.

How to Configure Segment Routing —IS-IS v4 node SID

Configuring Segment Routing

Before You Begin

Before configuring IS-IS to support segment routing you must first configure the segment routing feature in global configuration mode.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    segment-routing mpls

    4.    connected-prefix-sid-map

    5.    address-family ipv4

    6.    1.1.1.1/32 100


DETAILED STEPS
     Command or ActionPurpose
    Step 1enable


    Example: 
    Device# enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2configure terminal


    Example: 
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 segment-routing mpls

    Example: 
    Device(config-sr)# segment-routing mpls
     

    Enables the segment feature using the mpls data plane.

     
    Step 4 connected-prefix-sid-map

    Example: 
    Device(config-srmpls)# connected-prefix-sid-map
     

    Enters a sub-mode where you can configure address-family specific mappings for local prefixes and SIDs.

     
    Step 5 address-family ipv4

    Example: 
    Device(config-srmpls-conn)# address-family 1.1.1.1/32 100 range 1
     

    Specifies IP Version 4 address prefixes.

     
    Step 6 1.1.1.1/32 100

    Example: 
    Device(config-srmpls-conn-af)# 1.1.1.1/32 100
     

    Associates SID 100 w the address 1.1.1.1/32.

     

    Configuring Segment Routing on IS-IS Network

    Before You Begin

    Before you configure segment routing on IS-IS network, IS-IS must be enabled on your network.

    SUMMARY STEPS

      1.    router isis

      2.    net network-entity-title

      3.    metric-style wide

      4.    segment-routing mpls

      5.    exit

      6.    show isis segment-routing state


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 router isis

      Example: 
      Device(config-if)# router isis
       

      Enables the IS-IS routing protocol and enters router configuration mode.

       
      Step 2 net network-entity-title

      Example: 
      Device(config-router)# net 49.0000.0000.0003.00
       

      Configures network entity titles (NETs) for the routing instance.

       
      Step 3 metric-style wide

      Example: 
      Device(config-router)# metric-style wide
       

      Configures the device to generate and accept only wide link

      metrics.

       
      Step 4segment-routing mpls

      Example: 
      Device(config-router)# segment-routing mpls
       

      Configures segment routing operation state.

       
      Step 5 exit

      Example: 
      Device(config-router)# exit
       

      Exits segment routing mode and returns to the configuration terminal mode.

       
      Step 6 show isis segment-routing state

      Example: 
      Device# show is-is segment-routing state
       

      (Optional) Displays the current state of the IS-IS segment routing.

       

      The following example displays output from the show isis segment-routing state command for the segment routing under IS-IS: 

      Device# show isis segment-routing

ISIS protocol is registered with MFI
ISIS MFI Client ID:0x63
Tag 1 - Segment-Routing:
   SR State:SR_ENABLED
   Number of SRGB:1
   SRGB Start:16000, Range:8000, srgb_handle:0x4500AED0, srgb_state: created
   Address-family IPv4 unicast SR is configured
     Operational state:Enabled

      Configuring Prefix-SID for IS-IS

      This task explains how to configure prefix segment identifier (SID) index under each interface.

      Before You Begin

      Segment routing must be enabled on the corresponding address family.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    interface Loopback interface-instanceinterface-type

        4.    address-family { ipv4 | ipv6 } [ unicast ]

        5.    prefix-sid index index-value [ n-flag-clearlevel ] [ explicit-null ]

        6.    exit


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable

        Example: 
        Device# enable
         

        Enables privileged EXEC mode.

         
        Step 2 configure terminal

        Example: 
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3interface Loopback interface-instanceinterface-type


        Example: 
        Device(config)# interface loopback0 passive
         

        Specifies the interface loopback and interface type.

         
        Step 4address-family { ipv4 | ipv6 } [ unicast ]


        Example: 
        Device(config-if)# address-family ipv4 unicast
         

        Specifies the IPv4 or IPv6 address family, and enters router address family configuration mode.

         
        Step 5prefix-sid index index-value [ n-flag-clearlevel ] [ explicit-null ]


        Example: 
        Device(config-if-af)# prefix-sid index 1001 [n-flag-clear] [explicit-null]
         

        Configures the prefix-SID index for the interface.

         
        Step 6 exit

        Example: 
        Device(config-router)# exit
         

        Exits segment routing mode and returns to the configuration terminal mode.

         

        Configuring Prefix Attribute N-flag-clear

        By default, a flag called N-flag is set by IS-IS when advertising a SID which is associated with a loopback address. If you wish to clear this flag add explicit configuration.

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    interface loopback0

          4.    isis prefix-attributes n-flag-clear {Level-1|Level-2}


        DETAILED STEPS
           Command or ActionPurpose
          Step 1enable


          Example: 
          Device# enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2configure terminal


          Example: 
          Device# configure terminal
           

          Enters global configuration mode.

           
          Step 3 interface loopback0

          Example: 
          Device(config)# interface loopback0
           

          Enters interface configuration sub-mode.

           
          Step 4 isis prefix-attributes n-flag-clear {Level-1|Level-2}

          Example: 
          Device(config-if)# isis prefix-attributes n-flag-clear level-1
           

          Clears the prefix-SID attribute N-flag explicitly.

           

          Configuration Examples for Segment Routing —IS-IS v4 node SID

          Example: Configuring Segment Routing on IS-IS Network

          The following example shows how to configure segment routing under non-default SRGB mode: 

          enable
configure terminal
 segment-routing mpls
global-block 20000 24999
 !
 connected-prefix-sid-map
  address-family ipv4
   1.1.1.1/32 100 range 1
  exit-address-family
 !
router isis
 net 49.1111.1111.1111.00
 metric-style wide
 segment-routing mpls

          Example: Configuring Prefix Attribute N-Flag-Clear

          The following is an example for configuring prefix attribute n-flag-clear for interface loopback3: 

          Device(config)# interface loopback3
Device(config-if)# isis prefix n-flag-clear Clear N-flag
Device(config-if)# isis prefix n-flag-clear
Device(config-if)# isis prefix n-flag-clear

          Additional References

          Related Documents

          Related Topic

          Document Title

          Cisco IOS commands

          Cisco IOS Master Command List, All Releases http:/​/​www.cisco.com/​c/​en/​us/​td/​docs/​ios-xml/​ios/​mcl/​allreleasemcl/​all-book.html

          IP Routing ISIS commands

          Cisco IOS IP Routing ISIS commands http:/​/​www.cisco.com/​c/​en/​us/​td/​docs/​ios-xml/​ios/​mcl/​allreleasemcl/​all-book.html

          Technical Assistance

          Description

          Link

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

          Feature Information for Segment Routing—IS-IS v4 node SID

          Table 1 Feature Information for ISIS Segment Routing

          Feature Name

          Releases

          Feature Information

          Segment Routing—IS-IS v4 node SID

          Cisco IOS XE Release 3.16S

          The Segment Routing—ISIS v4 node SID feature provides support for segment routing on IS-IS networks.

          The following commands were introduced or modified: isis prefix-attributes n-flag-clear, isis segment-routing, show isis segment-routing state