Enabling Graceful Restart - Dell S4820T Configuration Manual

neighbor 100.10.92.9 local-as 6500
neighbor 100.10.92.9 no shutdown
neighbor 192.168.10.1 remote-as 65123
neighbor 192.168.10.1 update-source Loopback 0
neighbor 192.168.10.1 no shutdown
neighbor 192.168.12.2 remote-as 65123
neighbor 192.168.12.2 allowas-in 9
neighbor 192.168.12.2 update-source Loopback 0
neighbor 192.168.12.2 no shutdown
R2(conf-router_bgp)#R2(conf-router_bgp)#

Enabling Graceful Restart

Use this feature to lessen the negative effects of a BGP restart.
Dell Networking OS advertises support for this feature to BGP neighbors through a capability
advertisement. You can enable graceful restart by router and/or by peer or peer group.
NOTE: By default, BGP graceful restart is disabled.
The default role for BGP is as a receiving or restarting peer. If you enable BGP, when a peer that supports
graceful restart resumes operating, Dell Networking OS performs the following tasks:
• Continues saving routes received from the peer if the peer advertised it had graceful restart capability.
Continues forwarding traffic to the peer.
• Flags routes from the peer as Stale and sets a timer to delete them if the peer does not perform a
graceful restart.
• Deletes all routes from the peer if forwarding state information is not saved.
• Speeds convergence by advertising a special update packet known as an end-of-RIB marker. This
marker indicates the peer has been updated with all routes in the local RIB.
If you configure your system to do so, Dell Networking OS can perform the following actions during a
hot failover:
• Save all forwarding information base (FIB) and content addressable memory (CAM) entries on the line
card and continue forwarding traffic while the secondary route processor module (RPM) is coming
online.
• Advertise to all BGP neighbors and peer-groups that the forwarding state of all routes has been saved.
This prompts all peers to continue saving the routes they receive and to continue forwarding traffic.
• Bring the secondary RPM online as the primary and re-open sessions with all peers operating in No
Shutdown mode.
• Defer best path selection for a certain amount of time. This helps optimize path selection and results
in fewer updates being sent out.
To enable graceful restart, use the configure router bgp graceful-restart command.
• Enable graceful restart for the BGP node.
CONFIG-ROUTER-BGP mode
bgp graceful-restart
• Set maximum restart time for all peers.
CONFIG-ROUTER-BGP mode
bgp graceful-restart [restart-time time-in-seconds]
The default is 120 seconds.
Border Gateway Protocol IPv4 (BGPv4)
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