Deployment Guide

To view non-default values, use the show config command in CONFIGURATION ROUTER BGP mode or the show running-
config bgp command in EXEC Privilege mode.
Enabling BGP Neighbor Soft-Reconguration
BGP soft-reconguration allows for faster and easier route changing.
Changing routing policies typically requires a reset of BGP sessions (the TCP connection) for the policies to take eect. Such resets cause
undue interruption to trac due to hard reset of the BGP cache and the time it takes to re-establish the session. BGP soft recong allows
for policies to be applied to a session without clearing the BGP Session. Soft-recong can be done on a per-neighbor basis and can either
be inbound or outbound.
BGP soft-reconguration clears the policies without resetting the TCP connection.
To reset a BGP connection using BGP soft reconguration, use the clear ip bgp command in EXEC Privilege mode at the system
prompt.
When you enable soft-reconguration for a neighbor and you execute the clear ip bgp soft in command, the update database
stored in the router is replayed and updates are reevaluated. With this command, the replay and update process is triggered only if a route-
refresh request is not negotiated with the peer. If the request is indeed negotiated (after execution of clear ip bgp soft in), BGP
sends a route-refresh request to the neighbor and receives all of the peer’s updates.
To use soft reconguration (or soft reset) without preconguration, both BGP peers must support the soft route refresh capability, which is
advertised in the open message sent when the peers establish a TCP session.
To determine whether a BGP router supports this capability, use the show ip bgp neighbors command. If a router supports the
route refresh capability, the following message displays:
Received route refresh capability from peer.
If you specify a BGP peer group by using the peer-group-name argument, all members of the peer group inherit the characteristic
congured with this command.
• Clear all information or only specic details.
EXEC Privilege mode
clear ip bgp {* | neighbor-address | AS Numbers | ipv4 | peer-group-name} [soft [in | out]]
• *: Clears all peers.
• neighbor-address: Clears the neighbor with this IP address.
• AS Numbers: Peers’ AS numbers to be cleared.
• ipv4: Clears information for the IPv4 address family.
• peer-group-name: Clears all members of the specied peer group.
• Enable soft-reconguration for the BGP neighbor specied.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group-name} soft-reconfiguration inbound
BGP stores all the updates received by the neighbor but does not reset the peer-session.
Entering this command starts the storage of updates, which is required to do inbound soft reconguration. Outbound BGP soft
reconguration does not require inbound soft reconguration to be enabled.
Example of Soft-Recongration of a BGP Neighbor
The example enables inbound soft reconguration for the neighbor 10.108.1.1. All updates received from this neighbor are stored unmodied,
regardless of the inbound policy. When inbound soft reconguration is done later, the stored information is used to generate a new set of
inbound updates.
Dell>router bgp 100
neighbor 10.108.1.1 remote-as 200
neighbor 10.108.1.1 soft-reconfiguration inbound
Border Gateway Protocol IPv4 (BGPv4)
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