Controlling Route Importation - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

JUNOSe 11.1.x BGP and MPLS Configuration Guide

Controlling Route Importation

You can control how many routes a PE router can add to a particular VRF's forwarding
table by specifying a maximum limit and a warning threshold. When the router
attempts to add a route, it compares the limit you configure against a route count it
maintains for routes already in the VRF's forwarding table.
With a warning threshold configured, the following behavior takes place when the
PE router attempts to add a route:
With a limit configured, the following behavior takes place when the PE router
attempts to add a route:
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Configuring BGP VPN Services
To apply the new policy to routes that are already present in the BGP routing
table, you must use the clear ip bgp command to perform a soft clear or hard
clear of the current BGP session.
Behavior is different for outbound policies configured for peer groups for which
you have enabled Adj-RIBs-Out. If you change the outbound policy for such a
peer group and want to fill the Adj-RIBs-Out table for that peer group with the
results of the new policy, you must use the clear ip bgp peer-group command
to perform a hard clear or outbound soft clear of the peer group. You cannot
merely perform a hard clear or outbound soft clear for individual peer group
members because that causes BGP to resend only the contents of the Adj-RIBs-Out
table.
Example
host1(config-router)#neighbor allowas-in
Use the no version to prevent the acceptance of these routes, resulting in the
BGP speaker's discarding the routes.
See neighbor allowas-in.
When adding the route causes the route count to exceed the warning threshold
for the first time, the router adds the route and generates a
warning-threshold-exceeded log entry.
As long as the route count stays above the warning threshold, adding more routes
does not generate more warning-threshold-exceeded log entries.
If the route count fluctuates below and above the warning threshold due to route
deletions and additions, an interval of 5 minutes since the last
warning-threshold-exceeded log entry must pass before another
warning-threshold-exceeded log entry can be generated. This behavior prevents
the system log from being flooded with log entries.
When adding the route causes the route count to exceed the limit for the first
time, the router rejects the route and generates a limit-exceeded log entry.
As long as the route count stays at the limit, further attempts to add routes fail,
but do not generate any more limit-exceeded log entries.
If the route count fluctuates below and up to the limit due to route deletions and
additions, no further limit-exceeded log entries are generated until a 5-minute