BGP Persistence

This feature introduces support for the mechanism to preserve BGP routing details for a longer period from a failed BGP peer than the duration for which such routing information is maintained using the BGP long-lived graceful (LLGR) restart functionality. 

BGP LLGR allows a network operator to choose to maintain stale routing information from a failed BGP peer much longer than the traditional BGP graceful restart facility. You must explicitly configure BGP LLGR per NLRI and include provisions to prevent the spread of stale information to other peers that do not recognize and validate LLGR. LLGR provides the following benefits:

• Routes from failed nodes are retained for a configured time period (in the order of days). 
• You can examine per-NLRI LLGR negotiation states using appropriate show commands. 
• You can view whether LLGR is currently in effect for a peer, and if it is effective, the period after which it expires. 
• Stale routes retained by LLGR are explicitly marked in the output of the show bgp neighbor command. 
• Stale routes learned from other neighbors are explicitly marked in the output of the show bgp neighbor command (using well-defined communities).