User's Manual

Table Of Contents
455
Users Manual of CS-6306R
45.4.2.1.3 Configuring BGP Soft Reconfiguration
In general, BGP neighbors exchange all routes only when the connection is created; they then exchange only
the changed routes later. If the configured routing policy is changed, you must clear the BGP sessions before
you apply the changed routing policy to the received routes. However, clearing the BGP session can disable
the high-speed cache and seriously undermine network running. You are recommended to adopt the soft
reconfiguration function because it helps to configure and activate policy without clearing BGP sessions.
Currently, the new soft reconfiguration function can be applied to each neighbor. The new soft reconfiguration
is applied to the incoming update generated by neighbors, it is called incoming soft reconfiguration. When the
new soft reconfiguration is used to send the outgoing update to the neighbor, it is called outgoing soft
reconfiguration. After the incoming soft reconfiguration is run, new input policies validates. After the outgoing
soft reconfiguration is run, the new local output policy validates without resetting BGP session.
In order to generate the incoming update without resetting BGP session, the router of the local BGP session
should restore the received incoming update without modification. Whether the incoming update is received
or declined by the current incoming policy is not in the consideration. In this case, the memory will be badly
occupied. The outgoing reconfiguration has no extra memory cost, so it is always valid. You can trigger the
outgoing soft reconfiguration on the other side of the BGP session to validate the new local incoming policy.
To permit the incoming soft reconfiguration, you need to configure BGP to restore all received routing update.
The outgoing soft reconfiguration does not require pre-configuration.
Run the following command to configure BGP soft reconfiguration:
Command Purpose
Neighbor { ip-address }
soft-reconfiguration [inbound]
Configures BGP soft reconfiguration.
45.4.2.1.4 Resetting BGP Connection
Once two routers are defined as BGP neighbors, they will create a BGP connection and exchange route
choice information. If the BGP routing policy is modified afterwards, or if other configuration is changed, you
must reset the BGP connection to validate the changed configuration. Run one of the following commands to
reset the BGP connection.
Command Purpose
clear ip bgp * Resets all BGP connections.
clear ip bgp address
Resets a special BGP connection.