Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 181
Configuring BGP Fast Fall-Over
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10.68.164.1 10.68.165.1 10.68.166.1 10.68.167.1 10.68.168.1 10.68.169.1 10.68.170.1 10.68.171.1 10.68.172.1 10.68.173.1 10.68.174.1 10.68.175.1 10.68.176.1 10.68.177.1 10.68.178.1 10.68.179.1 10.68.180.1 10.68.181.1 10.68.182.1 10.68.183.1 10.68.184.1 10.68.185.1 Dell> Configuring 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 you enable fall-over, 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 enable the BGP fast fall-over feature, use the following command. To disable fast fall-over, use the [no] neighbor [neighbor | peer-group] fall-over command in CONFIGURATION ROUTER BGP mode. • Enable BGP Fast fall-Over. CONFIG-ROUTER-BGP mode neighbor {ip-address | peer-group-name} fall-over Examples of Verifying that Fast fall-Over is Enabled on a BGP Neighbor and a Peer-Group To verify that you enabled fast fall-over on a particular BGP neighbor, use the show ip bgp neighbors command. Because fast fallover is disabled by default, it appears only if it has been enabled (shown in bold). Dell#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 Border Gateway Protocol IPv4 (BGPv4) 181
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