Configuring Route Flap Dampening; Global Route Flap Dampening - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

JUNOSe 11.1.x BGP and MPLS Configuration Guide

Configuring Route Flap Dampening

Route flap dampening is a mechanism for minimizing instability caused by route
flapping. Route flapping occurs when a link is having a problem and is constantly
going up and down. Every time the link goes down, the upstream peer withdraws
the routes from all its neighbors. When the link comes back up again, the peer
advertises those routes globally. When the link problem appears again, the peer
withdraws the routes again. This process continues until the underlying problem is
fixed.
The router stores a penalty value with each route. Each time the route flaps, the
router increases the penalty by 1000. If the penalty for a route reaches a configured
suppress value, the router suppresses the route. That is, the router does not include
the route as a forwarding entry and does not advertise the route to BGP peers.
The penalty decrements by 50 percent for each half-life interval that passes. The
half-life interval resets when the route flaps and the penalty increments. The route
remains suppressed until the penalty falls below the configured reuse threshold, at
which point the router once again advertises the route. You can specify a
max-suppress-time for route suppression; after this interval passes, the router once
again advertises the route.
BGP creates a dampening parameter block for each unique set of dampening
parameters such as suppress threshold and reuse threshold used by BGP. For
example, if you have a route map that sets the dampening parameters to one set of
values for some routes and to another set of values for the remaining routes, BGP
uses and stores two dampening parameter blocks, one for each set.

Global Route Flap Dampening

Use the bgp dampening command if you want to enable route flap dampening with
the same values on all BGP routes, or on all routes matching the specified route map.
If you specify a route map, the router dampens only routes that are permitted by
the route map. For example:
bgp dampening
102
Configuring BGP Routing Policy
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.
Use the no version to remove the prefix list.
See neighbor prefix-list.
host1(config-router)#bgp dampening 8 600 2500 30 route-map 1