Dell PowerSwitch S4128F-ON OS10 Enterprise Edition User Guide Release 10.4.3.0 - Page 457

Configure BGP confederations OS10(config)# router bgp 65501 OS10(conf-router-bgp-65501)# confederation identifier 100 OS10(conf-router-bgp-65501)# confederation peers 65502 65503 65504 OS10(conf-router-bgp-65501)# neighbor 1.1.1.2 OS10(conf-router-neighbor)# remote-as 65502 OS10(conf-router-neighbor)# no shutdown OS10(conf-router-neighbor)# exit OS10(conf-router-bgp-65501)# neighbor 2.1.1.2 OS10(conf-router-neighbor)# remote-as 65503 OS10(conf-router-neighbor)# no shutdown OS10(conf-router-neighbor)# exit OS10(conf-router-bgp-65501)# neighbor 3.1.1.2 OS10(conf-router-neighbor)# remote-as 65504 OS10(conf-router-neighbor)# no shutdown OS10(conf-router-neighbor)# exit OS10(conf-router-bgp-65501)# end OS10# show running-configuration bgp ! router bgp 65501 confederation identifier 100 confederation peers 65502 65503 65504 ! neighbor 1.1.1.2 remote-as 65502 no shutdown ! neighbor 2.1.1.2 remote-as 65503 no shutdown ! neighbor 3.1.1.2 remote-as 65504 no shutdown Route dampening When EBGP routes become unavailable, they "flap" and the router issues both WITHDRAWN and UPDATE notices. A flap occurs when a route is withdrawn, readvertised after being withdrawn, or has an attribute change. The constant router reaction to the WITHDRAWN and UPDATE notices causes instability in the BGP process. To minimize this instability, configure penalties (a numeric value) for routes that flap. When that penalty value reaches a configured limit, the route is not advertised, even if the route is up, the penalty value is 1024. As time passes and the route does not flap, the penalty value decrements or decays. If the route flaps again, it is assigned another penalty. The penalty value is cumulative and adds underwithdraw, readvertise, or attribute change. When dampening applies to a route, its path is described by: History entry Dampened path Penalized path Entry that stores information on a downed route. Path that is no longer advertised. Path that is assigned a penalty. 1 Enable route dampening in ROUTER-BGP mode. dampening [half-life | reuse | max-suppress-time] • half-life - Number of minutes after which the penalty decreases (1 to 45, default 15). After the router assigns a penalty of 1024 to a route, the penalty decreases by half after the half-life period expires. • reuse - Number compares to the flapping route's penalty value. If the penalty value is less than the reuse value, the flapping route again advertises or is no longer suppressed (1 to 20000, default 750). Withdrawn routes are removed from the history state. Layer 3 457