Cisco ASR 9000 Series Routing Configuration Guide

PurposeCommand or Action
Soft reconfiguration enables the software to store the incoming updates
before apply policy if route refresh is not supported by the peer
(otherwise a copy of the update is not stored). The always keyword
forces the software to store a copy even when route refresh is
supported by the peer.
commit
Step 6
BGP Persistence
BGP persistence enables the local router to retain routes that it has learnt from the configured neighbor even
after the neighbor session is down. BGP persistence is also referred as Long Lived Graceful Restart (LLGR).
LLGR takes effect after graceful restart (GR) ends or immediately if GR is not enabled. LLGR ends either
when the LLGR stale timer expires or when the neighbor sends the end-of-RIB marker after it has revised its
routes. When LLGR for a neighbor ends, all routes from that neighbor that are still stale will be deleted. The
LLGR capability is signaled to a neighbor in the BGP OPEN message if it has been configured for that
neighbor. LLGR differs from graceful restart in the following ways.
•
It can be in effect for a much longer time than GR
•
LLGR stale routes are least preferred during route selection (bestpath computation).
•
An LLGR stale route will be advertised with the LLGR_STALE community attached if it is selected as
best path. It will not be advertised at all to routers that are not LLGR capable.
•
LLGR stale routes will not be deleted when the forwarding path to the neighbor is detected to be down
•
An LLGR stale route will not be deleted if the BGP session to the neighbor goes down multiple times
even if that neighbor does not re-advertise the route.
•
Any route that has the NO_LLGR community will not be retained.
BGP will not pass the updates containing communities 65535:6, 65535:7 to its neighbors until the neighbors
negotiate BGP persistence capabilities. The communities 65535:6 and 65535:7 are reserved for LLGR_STALE
and NO_LLGR respectively, BGP behavior maybe unpredictable if you have configured these communities
prior to release 5.2.2. We recommend not to configure the communities 65535:6 and 65535:7.
The BGP persistence feature is supported only on the following AFIs:
•
VPNv4 and VPNv6
•
RT constraint
•
Flow spec (IPv4, IPv6, VPNv4 and VPNv6)
•
Private IPv4 and IPv6 (IPv4/v6 address family inside VRF)
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
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Implementing BGP
BGP Persistence

Cisco ASR 9000 Series Specifications

General

Brand	Cisco
Model	ASR 9000 Series
Category	Network Router
Language	English