Reference Guide

Border Gateway Protocol IPv4 (BGPv4) | 209
10.68.181.1
10.68.182.1
10.68.183.1
10.68.184.1
10.68.185.1
FTOS>
BGP fast fall-over
By default, a BGP session is governed by the hold time. BGP routers typically carry large routing tables, so
frequent session resets are not desirable. The BGP fast fall-over feature reduces the convergence time
while maintaining stability. The connection to a BGP peer is immediately reset if a link to a directly
connected external peer fails.
When fall-over is enabled, BGP tracks IP reachability to the peer remote address and the peer local
address. Whenever either address becomes unreachable (for example, no active route exists in the routing
table for peer IPv6 destinations/local address), BGP brings down the session with the peer.
The BGP fast fall-over feature is configured on a per-neighbor or peer-group basis and is disabled by
default.
To disable Fast Fall-Over, use the
[no] neighbor [neighbor | peer-group] fall-over command in
CONFIGURATION ROUTER BGP mode
Use the
show ip bgp neighbors command as shown in in the example below to verify that fast fall-over is
enabled on a particular BGP neighbor. Note that since Fast Fall-Over is disabled by default, it will appear
only if it has been enabled.
FTOS#sh ip bgp neighbors
BGP neighbor is 100.100.100.100, remote AS 65517, internal link
Member of peer-group test for session parameters
BGP version 4, remote router ID 30.30.30.5
BGP state ESTABLISHED, in this state for 00:19:15
Last read 00:00:15, last write 00:00:06
Hold time is 180, keepalive interval is 60 seconds
Received 52 messages, 0 notifications, 0 in queue
Sent 45 messages, 5 notifications, 0 in queue
Received 6 updates, Sent 0 updates
Route refresh request: received 0, sent 0
Minimum time between advertisement runs is 5 seconds
Minimum time before advertisements start is 0 seconds
Capabilities received from neighbor for IPv4 Unicast :
MULTIPROTO_EXT(1)
ROUTE_REFRESH(2)
CISCO_ROUTE_REFRESH(128)
Command Syntax Command Mode Purpose
neighbor {ip-address |
peer-group-name} fall-over
CONFIG-ROUTER-BGP Enable BGP Fast Fall-Over