Connectivity Guide

Congure 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When EBGP routes become unavailable, they “ap” and the router issues both WITHDRAWN and UPDATE notices. A ap 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route is withdrawn, readvertised after being withdrawn, or has an attribute change.
The constant router reaction to the WITHDRAWN and UPDATE notices causes instability in the BGP process.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,
congure penalties (a numeric value) for routes that ap. When that penalty value reaches a congured 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 ap, the penalty value decrements or decays. If the route aps 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
Entry that stores information on a downed route.
Dampened path Path that is no longer advertised.
Penalized path 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 apping route’s penalty value. If the penalty value is less than the reuse value, the apping
route again advertises or is no longer suppressed (1 to 20000, default 750). Withdrawn routes are removed from the history state.
Layer 3
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