Reference Guide

Border Gateway Protocol IPv4 (BGPv4) | 199
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.
• 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 from your E-Series 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.
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.
With the graceful restart feature, FTOS enables the receiving/restarting mode by default. In receiver-only
mode, graceful restart saves the advertised routes of peers that support this capability when they restart.
However, the E-Series does not advertise that it saves these forwarding states when it restarts. This option
provides support for remote peers for their graceful restart without supporting the feature itself.
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.