The user first creates a targeted LDP session peer parameter template:
config>router>ldp>targ-session>peer-template template-name
Inside the template the user configures the common T-LDP session parameters or options shared by all peers using this template. These are the following:
bfd-enable, hello, hello-reduction, keepalive, local-lsr-id, and tunneling.
The tunneling option does not support adding explicit RSVP LSP names. LDP selects RSVP LSP for an endpoint in LDP-over-RSVP directly from the Tunnel Table Manager (TTM).
Then the user references the peer prefix list which is defined inside a policy statement defined in the global policy manager.
config>router>ldp>targ-session>peer-template-map peer-template template-name policy peer-prefix-policy
Each application of a targeted session template to a specific prefix in the prefix list results in the establishment of a targeted Hello adjacency to an LDP peer using the template parameters as long as the prefix corresponds to a router-id for a node in the TE database. The targeted Hello adjacency either triggers a new LDP session or is associated with an existing LDP session to that peer.
Up to five (5) peer prefix policies can be associated with a single peer template at all times. Also, the user can associate multiple templates with the same or different peer prefix policies. Thus multiple templates can match with a specific peer prefix. In all cases, the targeted session parameters applied to a specific peer prefix are taken from the first created template by the user. This provides a more deterministic behavior regardless of the order in which the templates are associated with the prefix policies.
Each time the user executes the above command, with the same or different prefix policy associations, or the user changes a prefix policy associated with a targeted peer template, the system re-evaluates the prefix policy. The outcome of the re-evaluation tells LDP if an existing targeted Hello adjacency needs to be torn down or if an existing targeted Hello adjacency needs to have its parameters updated on the fly.
If a /32 prefix is added to (removed from) or if a prefix range is expanded (shrunk) in a prefix list associated with a targeted peer template, the same prefix policy re-evaluation described above is performed.
The template comes up in the no shutdown state and therefore it takes effect immediately. After a template is in use, the user can change any of the parameters on the fly without shutting down the template. In this case, all targeted Hello adjacencies are updated.