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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

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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