16-5 debug ip bgp dampening access-list-number

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16-5 debug ip bgp dampening access-list-number

Syntax Description:

  • access-list-number ” IP access list number.

Purpose: To debug BGP events associated with dampening. The first form debugs all dampening events. The second form debugs only dampening events associated with routes identified by the IP access list. The IP access list number can be in the range from 1 to 199 or 1300 to 2699. Although it isn't necessary, use logging to store the results so that you can review them later.

Cisco IOS Software Release: 10.0

Example: Debug All BGP Dampening Events

In Figure 16-3, Router A is advertising network 199.172.2.0/24 via BGP to Router B. Dampening is enabled on Router B, and the 199.172.2.0/24 network on Router A is flapped by alternately bringing the interface up and down.

Figure 16-3. Scenario for Debugging BGP Dampening

graphics/16fig03.gif

 Router A  interface loopback 1   ip address 199.172.2.0 255.255.255.0   router bgp 1   neighbor 172.17.1.1 remote-as 2   ___________________________________________________________________________  Router B  router bgp 2   bgp dampening   neighbor 172.17.1.2 remote-as 1  

After Routers A and B have established a neighbor relationship, enable BGP dampening debugging on Router B, and flap the loopback interface on Router A:

 Router B logging buffered rtrB#  debug ip bgp dampening  rtrB#  show logging  Syslog logging: enabled (0 messages dropped, 0 flushes, 0 overruns)     Console logging: level debugging, 297 messages logged     Monitor logging: level debugging, 0 messages logged     Buffer logging: level debugging, 63 messages logged     Trap logging: level informational, 52 message lines logged Log Buffer (4096 bytes): 03:26:07: BGP(0): Created dampening structures with halflife time 15,  reuse/suppress 750/2000 03:26:43: BGP(0): charge penalty for 199.172.2.0/24 path 1 with halflife-time 15  reuse/suppress 750/2000 03:26:43: BGP(0): flapped 1 times since 00:00:00. New penalty is 1000 03:27:39: BGP(0): charge penalty for 199.172.2.0/24 path 1 with halflife-time 15  reuse/suppress 750/2000 03:27:39: BGP(0): flapped 2 times since 00:00:56. New penalty is 1961 03:28:32: BGP(0): charge penalty for 199.172.2.0/24 path 1 with halflife-time 15  reuse/suppress 750/2000 03:28:32: BGP(0): flapped 3 times since 00:01:49. New penalty is 2886 03:29:05: BGP(0): suppress 199.172.2.0/24 path 1 for 00:28:40 (penalty 2819) 03:29:05: halflife-time 15, reuse/suppress 750/2000 03:57:52: BGP(0): Unsuppressed 199.172.2.0/24, path 1 

If you want debugging information for a particular prefix, use the second form of this command. For example, to debug dampening for prefix 199.172.2.0/24, use the following configuration:

 Router B  access-list 1 permit 199.172.2.0 0.0.0.255  rtrB#  debug ip bgp dampening 1  
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Cisco[r] BGP-4 Command and Configuration Handbook
Cisco BGP-4 Command and Configuration Handbook
ISBN: 1587055732
EAN: 2147483647
Year: 2001
Pages: 300

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