This feature adds the support of multiple instances of the Router Information LSA as described in RFC 7770, Extensions to OSPF for Advertising Optional Router Capabilities.
The original method of advertising router capabilities used options fields in LSAs and hello packets. However, this method is not extensible because of the limited size of the options field. The RFC 4970, Extensions to OSPF for Advertising Optional Router Capabilities, defined the Router Information LSA which can carry multiple router capability TLVs. It also defined a single TLV called the Router Informational Capabilities TLV to carry all previously defined capabilities in the options field in LSAs and hello packets. The SR OS supports RFC 4970.
RFC 7770 deprecated RFC 4970 by adding the ability to send multiple instances of the Router Information LSA to circumvent the maximum LSA size of 64 kbytes.
There is no CLI to enable the support of multiple instances of the Router Information LSA. The existing Router Information Capabilities TLVs is carried as the first TLV (Opaque ID 0) of the first instance (instance ID 0) of the Router Information LSA. The existing router information TLVs, such as the OSPFv2 SR-Algorithm TLV and the SID/Label Range TLV, are sent in the first instance of the Router Information LSA.
If a router information TLV is received in multiple instances of the Router Information LSA, the default behavior is to process the one in the lowest instance ID and ignore the other ones.