IS-IS or OSPF interfaces are associated with one or more adjacency sets using the following CLI. Both numbered and unnumbered interfaces can be assigned to the same adjacency set.
config
router
isis
interface
[no] adjacency-set <id>
[no] adjacency-set <id>
[no] adjacency-set <id>
config
router
ospf
area
interface
[no] adjacency-set <id>
[no] adjacency-set <id>
[no] adjacency-set <id>
If an interface is assigned to an adjacency set, then a common adjacency SID value is advertised for every interface in the set, in addition to the adjacency SID corresponding to the IPv4 and or IPv6 adjacency for the interface. Each IS-IS or OSPF advertisement therefore contains two adjacency SID TLVs for an address family:
an adjacency SID for the interface (a locally-unique value).
an adjacency SID TLV for the adjacency set.
This TLV is distinguished by having the S-bit (IS-IS) or G-bit (OSPF) in the flags field set to 1. Its value is the same as other adjacency SIDs in the set at that node.
By default, both the adjacency SID for an interface and the adjacency SID for a set are dynamically allocated by the system. However, it is possible for the user to configure an alternative, static value for the SID (see Provisioning Adjacency SID Values for an Adjacency Set for more information).
A maximum of 32 interfaces can be bound to a common adjacency set. Configuration of more than 32 interfaces is blocked by the system and a CLI error is generated.
Only point-to-point interfaces can be assigned to an adjacency set.
If a user attempts to assign an IES interface to an adjacency set, the system generates a CLI warning and segment routing does not program the association.
The IGP blocks the configuration of an adjacency set under an interface when the adjacency set has not yet been created under segment-routing.
In IS-IS, it is possible to add Layer 1, Layer 2, or a mix of Layer 1 and Layer 2 adjacencies to the same adjacency set.