Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 131)

Multi-Service IronWare Routing Configuration Guide 103
53-1003033-02
Filtering
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. Refer to
“Clearing and resetting BGP4 routes in the IP route table” on page 109.
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.
Brocade(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.