Quick Reference Guide

PowerConnect B-Series TI24X Configuration Guide 845
53-1002269-02
Updating route information and resetting a neighbor session
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This example shows the active configuration for a route map called “setcomm“.
Syntax: show route-map [<map-name>]
Updating route information and resetting a neighbor session
The following sections describe ways to update route information with a neighbor, reset the session
with a neighbor, and close a session with a neighbor.
Whenever you change a policy (ACL, route map, and so on) that affects the routes that the Layer 3
Switch learns from a BGP4 neighbor or peer group of neighbors, you must enter a command to
place the changes into effect. The changes take place automatically, but only affect new route
updates. To make changes retroactive for routes received or sent before the changes were made,
you need to enter a clear command.
You can update the learned routes using either of the following methods:
• Request the complete BGP4 route table from the neighbor or peer group. You can use this
method if the neighbor supports the refresh capability (RFCs 2842 and 2858).
• Clear (reset) the session with the neighbor or peer group. This is the only method you can use if
the neighbor does not support the refresh capability.
Each of these methods is effective, but can be disruptive to the network. The first method adds
overhead while the Layer 3 Switch learns and filters the neighbor or group entire route table, while
the second method adds more overhead while the devices re-establish their BGP4 sessions.
You also can clear and reset the BGP4 routes that have been installed in the IP route table. Refer to
“Clearing and resetting BGP4 routes in the IP route table” on page 851.
Using soft reconfiguration
The soft reconfiguration feature places policy changes into effect without resetting the BGP4
session. Soft reconfiguration does not request the neighbor or group to send its entire BGP4 table,
nor does the feature reset the session with the neighbor or group. Instead, the soft reconfiguration
feature stores all the route updates received from the neighbor or group. When you request a soft
reset of inbound routes, the software performs route selection by comparing the policies against
the stored route updates, instead of requesting the neighbor BGP4 route table or resetting the
session with the neighbor.
When you enable the soft reconfiguration feature, it sends a refresh message to the neighbor or
group if the neighbor or group supports dynamic refresh. Otherwise, the feature resets the
neighbor session. This step is required to ensure that the soft reconfiguration feature has a
complete set of updates to use, and occurs only once, when you enable the feature. The feature
accumulates all the route updates from the neighbor, eliminating the need for additional refreshes
or resets when you change policies in the future.
To use soft reconfiguration:
• Enable the feature.
• Make the policy changes.
• Apply the changes by requesting a soft reset of the inbound updates from the neighbor or
group.