friendrelop.blogg.se

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, R2 has learned route 1.1.1.1/32 from R1: R2# show ip bgpīGP table version is 2, local router ID is 192.168.12.2 I’ll keep it simple and use the global option for now. R2(config-router)# bgp dampening route-map DAMPENING R2(config-route-map)# match ip address R1_L0 R2(config)# route-map DAMPENING permit 10 This way, you can specify which routes you want to enable dampening for: R2(config)# ip access-list standard R1_L0 The alternative is to include a route-map. R2(config-router)# bgp dampening Route-Map This is how to enable it: R2(config)# router bgp 2 When you enable BGP route dampening globally, it affects all routes. We have two options to configure BGP route dampening: R1 has a loopback interface that we advertise through BGP. There are two routers, each in their own AS. I’m using IOSv Software version 15.9(3)M2. Let’s see how we configure BGP dampening. The maximum suppress time is 60 minutes by default. The maximum suppress limit ensures that a route won’t be dampened forever. When the penalty is below 50% of the reuse limit, the penalty is removed from the route. Once the penalty is below the reuse limit of 750, the route can be used again and advertised to other BGP routers. Another 15 minutes and the penalty is 500.After another 15 minutes, the penalty is 1000.The penalty is 4000 and the half-life time is 15 minutes.Once the penalty is below 50% of the reuse limit, the penalty is removed completely.To install or advertise the route again, the penalty has to be lower than a reuse limit.When half-life is reached, the penalty is reduced by 50%.

When the router learns again about a route with a penalty, the half-life timer starts.Once the route is dampened, the router won’t install the route in the routing table nor advertise it to other BGP neighbors.When the route exceeds the suppress limit, the route is dampened.Each time a route flaps, the penalty is increased by 1000.I included the default values for Cisco IOS. Let’s take a look at how BGP route dampening works.