Reference Guide

154 | Border Gateway Protocol
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Enable graceful restart
Use this feature to lessen the negative effects of a BGP restart. FTOS 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.
The default role for BGP on is as a receiving or restarting peer. If you enable BGP, when a peer that
supports graceful restart resumes operating, FTOS 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, FTOS can perform the following actions during a hot failover:
• Save all FIB and CAM entries on the line card and continue forwarding traffic while the secondary
RPM is coming online.
• 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.
Enable graceful restart using the
configure router bgp graceful-restart command. The table below shows
the command and its available options:
BGP graceful restart is active only when the neighbor becomes established. Otherwise it is disabled.
Graceful-restart applies to all neighbors with established adjacency.
Note: By default, BGP graceful restart is disabled.
Command Syntax Command Mode Usage
bgp graceful-restart CONFIG-ROUTER-BGP Enable graceful restart for the BGP node.
bgp graceful-restart [restart-time
time-in-seconds]
CONFIG-ROUTER-BGP Set maximum restart time for all peers. Default
is 120 seconds.
bgp graceful-restart [stale-path-time
time-in-seconds]
CONFIG-ROUTER-BGP Set maximum time to retain the restarting peer’s
stale paths. Default is 360 seconds.
bgp graceful-restart [role
receiver-only
]
CONFIG-ROUTER-BGP Local router supports graceful restart as a
receiver only.