■ 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.
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:
■ 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.
With a limit configured, the following behavior takes place when the PE router
attempts to add a route:
■ 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
452 ■ Configuring BGP VPN Services
JUNOSe 11.1.x BGP and MPLS Configuration Guide
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