Cisco Cisco IOS Software Release 12.2(27)SBC
BGP Support for Nonstop Routing (NSR) with Stateful Switchover (SSO)
Information About BGP Support for Nonstop Routing (NSR) with Stateful Switchover (SSO)
3
Cisco IOS Release 12.2(28)SB
BGP NSR with SSO feature is configured, in the event of an RP switchover, the PE router uses BGP NSR
with SSO to maintain BGP state for eBGP peering sessions with CEs that are not NSF-aware (see
with SSO to maintain BGP state for eBGP peering sessions with CEs that are not NSF-aware (see
). Additionally, the BGP NSR with SSO feature dynamically detects NSF-aware peers and runs
graceful restart with those CE routers. For eBGP peering sessions with NSF-aware peers and for internal
BGP (iBGP) sessions with BGP Route Reflectors (RRs) in the service provider core, the PE uses NSF
to maintain BGP state. BGP NSR with SSO, thus, enables service providers to provide the benefits of
NSF with the additional benefits of NSR without requiring CE routers to be upgraded to support BGP
graceful restart.
BGP (iBGP) sessions with BGP Route Reflectors (RRs) in the service provider core, the PE uses NSF
to maintain BGP state. BGP NSR with SSO, thus, enables service providers to provide the benefits of
NSF with the additional benefits of NSR without requiring CE routers to be upgraded to support BGP
graceful restart.
Figure 1
BGP NSR with SSO Operations During an RP Switchover
BGP NSR with SSO is supported in BGP peer, BGP peer group, and BGP session template
configurations. To configure support for BGP NSR with SSO in BGP peer and BGP peer group
configurations, use the neighbor ha-mode sso command in address family configuration mode for IPv4
VRF address family BGP peer sessions. To include support for Cisco BGP NSR with SSO in a peer
session template, use the ha-mode sso command in session-template configuration mode.
configurations. To configure support for BGP NSR with SSO in BGP peer and BGP peer group
configurations, use the neighbor ha-mode sso command in address family configuration mode for IPv4
VRF address family BGP peer sessions. To include support for Cisco BGP NSR with SSO in a peer
session template, use the ha-mode sso command in session-template configuration mode.
Benefits of BGP NSR with SSO
•
Minimizes services disruptions—BGP NSR with SSO reduces impact on customer traffic during RP
switchovers (scheduled or unscheduled events), extending HA deployments and benefits at the edge.
switchovers (scheduled or unscheduled events), extending HA deployments and benefits at the edge.
•
Enhances high-availability NSF and SSO deployment at the edge—BGP NSR with SSO allows
incremental deployment by upgrading the provider edge with the NSR capability so that
customer-facing edge routers are synchronized automatically and no coordination or NSF awareness
is needed with the customer side Cisco or third-party customer edge routers. The BGP NSR feature
dynamically detects NSF-aware peers and runs graceful restart with those CE routers.
incremental deployment by upgrading the provider edge with the NSR capability so that
customer-facing edge routers are synchronized automatically and no coordination or NSF awareness
is needed with the customer side Cisco or third-party customer edge routers. The BGP NSR feature
dynamically detects NSF-aware peers and runs graceful restart with those CE routers.
•
Provides transparent route convergence—BGP NSR with SSO eliminates route flaps by keeping
BGP state on both active and standby RPs and ensures continuous packet forwarding with minimal
packet loss during RP failovers.
BGP state on both active and standby RPs and ensures continuous packet forwarding with minimal
packet loss during RP failovers.