Configuring IS-IS Flex-Algorithm Participation

Up to seven Flex-Algorithms in the range 128 to 255 can be configured for IS-IS. Use the participate command to configure participation for the specific algorithm. If a locally configured FAD exists, advertise this definition by using the advertise command. A router is not required to advertise a configured FAD to participate in a Flex-Algorithm.

If a Flex-Algorithm is enabled to participate or advertise the FAD, it is configured and active for all configured IS-IS areas.

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

config>router>isis
        — flexible-algorithms
            — 		[no] flex-algo flex-algo
                — advertise fad-name
                — no advertise
                — [no] loopfree-alternates
                — [no] participate
            — [no] shutdown
Note: When a router participates in Flex-Algorithms, it will only advertise support for the Flex-Algorithm where the router can comply with the winning FAD, provided that at least one FAD exists for this algorithm.

The following is a sample configuration output for Flex-Algorithm participation:

isis 0
    flexible-algorithms
      flex-algo 128
        advertise "My128"
        participate
      exit
      no shutdown
    exit

The following output is an example of IS-IS router capability when a FAD is advertised:

*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  : 0x94                   Checksum  : 0x4ae0   Lifetime  : 969
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 
TLVs :
  Supp Protocols:
    Protocols     : IPv4
  IS-Hostname   : Dut-B
  Router ID   :
    Router ID   : 10.20.1.2
Router Cap : 10.20.1.2, D:0, S:0
    TE Node Cap : B E M  P
    SR Cap: IPv4 MPLS-IPv6
       SRGB Base:20000, Range:10001
    SR Alg: metric based SPF, 128
    Node MSD Cap: BMI : 12 ERLD : 15
    FAD Sub-Tlv:
        Flex-Algorithm   : 128
        Metric-Type      : delay
        Calculation-Type : 0
        Priority         : 100
        Flags: M