In order to enable IPv6 TE on the router, a new parameter referred to as IPv6 TE Router ID must have a valid IPv6 address. The following CLI command is used to configure the parameter:
configure>router>ipv6-te-router-id interface interface-name
The IPv6 TE Router ID is a mandatory parameter and allows the router to be uniquely identified by other routers in an IGP TE domain as being IPv6 TE capable. IS-IS advertises this information using the IPv6 TE Router ID TLV as explained in TE Attributes Supported in IGP and BGP-LS.
When the command is not configured, or the no form of the command is configured, the value of the IPv6 TE Router ID parameter reverts to the preferred primary global unicast address of the system interface. The user can also explicitly enter the name of the system interface to achieve the same outcome.
In addition, the user can specify a different interface and the preferred primary global unicast address of that interface is used instead. Only the system or a loopback interface is allowed since the TE router ID must use the address of a stable interface.
This address must be reachable from other routers in a TE domain and the associated interface must be added to IGP for reachability. Otherwise, IS-IS withdraws the advertisement of the IPv6 TE Router ID TLV.
When configuring a new interface name for the IPv6 TE Router ID, or when the same interface begins using a new preferred primary global unicast address, IS-IS immediately floods the new value.
If the referenced system is shut down or the referenced loopback interface is deleted or is shut down, or the last IPv6 address on the interface is removed, IS-IS withdraws the advertisement of the IPv6 TE Router ID TLV.