Hi Christian,
1.2 What is route-flap dampening ?
If a threshold of the number of pairs of withdrawals/announcements (=flap) is exceeded in a given timeframe the prefix is held down for a
scheduled SW upgrade of backbone router failed:
- reload after SW upgrade 1 flap - new SW crashed 1 flap - reload with old SW 1 flap ------ 3 flaps within 10 minutes
You regard a withdrawal + announcement as 1 flap, right? Look at this: router-a#sh ip bgp 195.206.64.168 BGP routing table entry for 195.206.64.168/30, version 6 Paths: (1 available, best #1) 65001 65002 192.168.1.1 from 192.168.1.1 Origin IGP, valid, external, best Now the BGP session between AS65001 and AS65002 is reset... router-a#sh ip bgp 195.206.64.168 BGP routing table entry for 195.206.64.168/30, version 7 Paths: (1 available, no best path) 65001 65002 (history entry) 192.168.1.1 from 192.168.1.1 Origin IGP, external Dampinfo: penalty 1000, flapped 1 times in 00:00:00 ...the route 195.206.64.168/30 becomes a history entry. The BGP session comes up again... router-a#sh ip bgp 195.206.64.168 BGP routing table entry for 195.206.64.168/30, version 8 Paths: (1 available, best #1) 65001 65002 192.168.1.1 from 192.168.1.1 Origin IGP, valid, external, best Dampinfo: penalty 1480, flapped 2 times in 00:00:32 ...and the route is back, but flapped 2 times! The reset of the BGP session could be caused by a reload of the AS65002 router and results in 2 flaps. It seems that the cisco definition of 'one flap' is different from the one in your paper, or am I overlooking something? (btw, it's not clear to me why the penalty is 1480 already after 32 seconds) --- Thomas