LDP Hello interval

The LDP hello interval controls how often the device sends out LDP Hello messages. Hello messages are used to maintain LDP adjacencies between the device and its LDP peers.

You can set the interval for LDP Link Hello messages (LDP Hello messages multicast to all routers on the sub-net), as well as for LDP Targeted Hello messages (LDP Hello messages unicast to a specific address, such as a VLL peer):

• For targeted LDP adjacencies—The LDP Hello Interval can only be set globally. When a Hello Interval is not set for targeted LDP adjacencies, then the global default value is used.
• For link LDP adjacencies—The LDP Hello Interval can be set globally which applies to all LDP interfaces or on a per-interface basis. The LDP Hello Interval values in Link LDP adjacencies are determined by the following procedure in the order.
  1. When the Hello Interval is set per-interface, this value is used.
  2. When the Hello Interval is not set per-interface, then the value set for LDPs globally is used.
  3. When the Hello Interval is not set either globally or per-interface, the global default value is used.

     When a Hello adjacency already exists, the adjacency remains up and any new configured interval takes effect upon the expiration of the current Hello Interval timer. Consequently, the next and subsequent hello messages are sent at the new interval.