Configuring BGP
Configuring Basic BGP Features
IPC-299
Cisco IOS IP Configuration Guide
A soft reset updates the routing table for inbound and outbound routing updates. Cisco IOS software
Release 12.1 and later releases support soft reset without any prior configuration. This soft reset allows
the dynamic exchange of route refresh requests and routing information between BGP routers, and the
subsequent re-advertisement of the respective outbound routing table. There are two types of soft reset:
•When soft reset is used to generate inbound updates from a neighbor, it is called dynamic inbound
soft reset.
•When soft reset is used to send a new set of updates to a neighbor, it is called outbound soft reset.
To use soft reset without preconfiguration, 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. Routers running
Cisco IOS software releases prior to Release 12.1 do not support the route refresh capability and must
clear the BGP session using the neighbor soft-reconfiguration router configuration command,
described in “Configuring BGP Soft Reset Using Stored Routing Policy Information.” Clearing the BGP
session in this way will have a negative impact upon network operations and should only be used as a
last resort.
Resetting a Router Using BGP Dynamic Inbound Soft Reset
If both the local BGP router and the neighbor router support the route refresh capability, you can perform
a dynamic soft inbound reset. This type of reset has the following advantages over a soft inbound reset
using stored routing update information:
•Does not require preconfiguration
•Does not require additional memory for storing routing update information
To determine whether a router supports the route refresh capability, use the show ip bgp neighbors
command in EXEC mode:
If all the BGP routers support the route refresh capability, you can use the dynamic soft reset method for
resetting the inbound routing table. To perform a dynamic soft reset of the inbound routing table, use the
following command in EXEC mode:
See the “BGP Soft Reset Examples” section at the end of this chapter for examples of both types of BGP
soft resets.
Command Purpose
Router# show ip bgp neighbors
ip-address
Displays whether a neighbor supports the route refresh capability.
If the specified router supports the route refresh capability, the following
message is displayed: Received route refresh capability from peer.
Command Purpose
Router# clear ip bgp {* |
neighbor-address | peer-group-name}
soft in
Performs a dynamic soft reset on the connection specified in the command.
The neighbor-address argument specifies the connection to be reset. Use the
* keyword to specify that all connections be reset.