Configuring IS-IS Flex-Algorithm Prefix Node SID

The prefix node SID (IPv4 and/or IPv6) must be assigned for each participating Flex-Algorithm.

The Flex-Algorithm SIDs are allocated from the label block assigned to SR and configuring a special range is not required.

Note: Flex-Algorithm node SIDs can be configured for IPv4 and/or IPv6 prefixes.

Use the following syntax to configure the prefix node SIDs for IS-IS Flex-Algorithms.

config>router>isis>interface
        — ipv4-node-sid
        — flex-algo
            — ipv4-node-sid index <value>
            — ipv4-node-sid label <value>
            — no ipv4-node-sid
            — ipv6-node-sid index <value>
            — ipv6-node-sid label <value>
            — no ipv6-node-sid

The following is a sample configuration output for Flex-Algorithm prefix node SIDs:

router
  mpls-labels
    sr-labels start 20000 end 30000
  exit
  interface "Loopback0"
    address 10.20.1.2/32
    loopback
    no shutdown
  exit
  isis 0
    segment-routing
      prefix-sid-range global
      no shutdown
    exit
    interface "Loopback0"
      ipv4-node-sid index 2
      passive
      flex-algo 128
        ipv4-node-sid index 12
      exit
      no shutdown
    exit

The following output is an example of the Level 2 database of an advertised IS-IS:

A:Dut-B# show router isis database Dut-B.00-00 detail level 2
===============================================================================
Rtr Base ISIS Instance 0 Database (detail)
===============================================================================
Displaying Level 2 database
-------------------------------------------------------------------------------
LSP ID    : Dut-B.00-00                                 Level     : L2
Sequence  : 0x9d                   Checksum  : 0x38e9   Lifetime  : 626
Version   : 1                      Pkt Type  : 20       Pkt Ver   : 1
Attributes: L1L2                   Max Area  : 3        Alloc Len : 1492
SYS ID    : 4900.0000.0002         SysID Len : 6        Used Len  : 223
……<snip>……
  TE IP Reach   :
    Default Metric  : 10
    Control Info:    , prefLen 30
    Prefix   : 10.10.10.0
    Default Metric  : 0
    Control Info:   S, prefLen 32
    Prefix   : 10.20.1.2
    Sub TLV   :
      Prefix-SID Index:2, Algo:0, Flags:NnP
      Prefix-SID Index:12, Algo:128, Flags:NnP
    Default Metric  : 10
    Control Info:    , prefLen 30
    Prefix   : 10.10.10.8
...<snip>...