BGP Soft Reconfiguration

When a local BGP speaker is configured to apply soft-reconfiguration inbound the speaker will accept ALL prefixes from the remote peer and store them in a separate memory buffer. The prefixes are then processed via the inbound filters and the resulting information imported into Adj-RIB-In and finally to the BGP table. Every time the local policy changes, there is no need to re-establish the peering session but simply apply the filters to the stored information.

R1#show run | s bgp
router bgp 123
 no synchronization
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 12.1.1.2 remote-as 123
 neighbor 12.1.1.2 next-hop-self
 neighbor 12.1.1.2 send-community
 neighbor 13.1.1.3 remote-as 123
 neighbor 13.1.1.3 next-hop-self
 neighbor 13.1.1.3 send-community
 neighbor 15.1.1.5 remote-as 500
 neighbor 15.1.1.5 capability orf prefix-list send
 neighbor 15.1.1.5 soft-reconfiguration inbound
 neighbor 15.1.1.5 prefix-list ALLOW-PREFIX in
 no auto-summary
ip bgp-community new-format

R5#
router bgp 1500
 no synchronization
 bgp log-neighbor-changes
 network 5.5.5.0 mask 255.255.255.0
 network 10.0.0.0 mask 255.255.255.0
 network 10.0.1.0 mask 255.255.255.0
 network 10.0.2.0 mask 255.255.255.0
 network 10.0.3.0 mask 255.255.255.0
 network 55.55.55.0 mask 255.255.255.0
 neighbor 15.1.1.1 remote-as 123
 neighbor 15.1.1.1 send-community
 neighbor 15.1.1.1 capability orf prefix-list receive
 neighbor 15.1.1.1 soft-reconfiguration inbound
 no auto-summary
ip bgp-community new-format