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Syntax Description:

• prefix— IP address of the prefix to display.

• mask— Display prefix with a specific network mask.

• mask-length— Bit length of the mask.

• line— Regular expression. See Appendix B.

• list-number— Regular expression access list number. The range of values is 1 to 199.

• quoted-line— Regular expression in quotes.

Purpose: To display flap statistics for routes in the BGP table.

Cisco IOS Software Release: 11.0

Example: Display BGP Flap Statistics

A route flap occurs when a route is withdrawn and then later readvertised. This usually happens when an interface is going from the UP state to the DOWN state repeatedly. You can view the number of times a route has flapped using the show ip bgp flap-statistics command. This assumes that BGPP dampening has been enabled on the router.

rtrA#show ip bgp flap-statistics

BGP table version is 9, local router ID is 10.1.1.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete



   Network          From            Flaps Duration Reuse    Path

*d 172.16.2.0/24    10.1.1.1        3     00:02:55 00:28:10 1

The following list explains some of the fields that appear in the preceding output from the show ip bgp flap-statistics command.

• BGP table version— Whenever the BGP table changes, the version number is incremented.

• local router ID— The highest IP address assigned to an interface. If loopbacks are used, the router ID is the highest IP address assigned to a loopback interface. The router ID can be changed using the bgp router-id configuration command (see section 3-17).

• Status codes

  s— The entry is suppressed (see Chapter 8 and section 8-32).

  *— The entry is valid.

  d— The prefix is dampened.

  h— Dampening is enabled for the prefix (see sections 3-9 through 3-12).

  >— If there are multiple entries for the prefix, this indicates the best route.

  i— The prefix was learned via IBGP. This is the i to the left of the network entry.

• Origin codes

  i— Routes installed using the network command.

  e— Routes learned via EGP.

  ?— Routes learned via redistribution.

• Network— Prefix entry in the table. If a mask is not listed, the prefix is using the standard mask for the class of the entry.

• From— Next-hop attribute advertised by the BGP neighbor. A value of 0.0.0.0 indicates that the prefix was locally originated (see section 8-17).

• Flaps— The number of times the prefix has flapped.

• Duration— Time since the first flap.

• Reuse— Time until the prefix is undampened.

• Path— A list of the autonomous system paths leading back to the prefix.

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