Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 517)

Updating route information and resetting a neighbor session
The following sections describe how to update route information with a neighbor, reset a session with a
neighbor, and close a session with a neighbor.
Any change to a policy (ACL, route map, and so on) is automatically applied to outbound routes that are
learned from a BGP4 neighbor or peer group after the policy change occurs. However, you must reset
the neighbor to update existing outbound routes.
Any change to a policy is automatically applied to inbound routes that are learned after the policy
change occurs. However, to apply the changes to existing inbound routes (those inbound routes that
were learned before the policy change), you must reset the neighbors to update the routes using one 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). Most devices today support this
capability.
• Clear (reset) the session with the neighbor or peer group. This is the only method you can use if soft
reconfiguration is enabled for the neighbor.
You also can clear and reset the BGP4 routes that have been installed in the IP route table.
Using soft reconfiguration
The soft reconfiguration feature applies policy changes without resetting the BGP4 session. Soft
reconfiguration does not request the neighbor or group to send the entire BGP4 table, nor does the
feature reset the session with the neighbor or group. Instead, soft reconfiguration 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.
Enabling soft reconfiguration
To configure a neighbor for soft reconfiguration, enter a command such as the following.
device(config-bgp)# neighbor 10.10.200.102 soft-reconfiguration inbound
This command enables soft reconfiguration for updates received from 10.10.200.102. The software
dynamically resets the session with the neighbor, then retains all route updates from the neighbor
following the reset.
Syntax: [no] neighbor ip-addr | peer-group-name soft-reconfiguration inbound
Updating route information and resetting a neighbor session
FastIron Ethernet Switch Layer 3 Routing Configuration Guide 517
53-1003087-04