Administrator Guide

○ reuse: the range is from 1 to 20000. This number is compared to the flapping route’s Penalty value. If the Penalty value
is less than the reuse value, the flapping route is once again advertised (or no longer suppressed). The default is 750.
○ suppress: the range is from 1 to 20000. This number is compared to the flapping route’s Penalty value. If the Penalty
value is greater than the suppress value, the flapping route is no longer advertised (that is, it is suppressed). The default
is 2000.
○ max-suppress-time: the range is from 1 to 255. The maximum number of minutes a route can be suppressed. The
default is four times the half-life value. The default is 60 minutes.
● Clear all information or only information on a specific route.
EXEC Privilege
clear ip bgp dampening [ip-address mask]
● View all flap statistics or for specific routes meeting the following criteria.
EXEC or EXEC Privilege mode
show ip bgp flap-statistics [ip-address [mask]] [filter-list as-path-name] [regexp
regular-expression]
○ ip-address [mask]: enter the IP address and mask.
○ filter-list as-path-name: enter the name of an AS-PATH ACL.
○ regexp regular-expression: enter a regular express to match on.
By default, the path selection is deterministic, that is, paths are compared irrespective of the order of their arrival. You can
change the path selection method to non-deterministic, that is, paths are compared in the order in which they arrived
(starting with the most recent). Furthermore, in non-deterministic mode, the software may not compare MED attributes
though the paths are from the same AS.
● Change the best path selection method to non-deterministic.
Change the best path selection method to non-deterministic.
CONFIG-ROUTER-BGP mode
bgp non-deterministic-med
NOTE:
When you change the best path selection method, path selection for existing paths remains unchanged until you
reset it by entering the clear ip bgp command in EXEC Privilege mode.
To view the BGP configuration, use the show config command in CONFIGURATION ROUTER BGP mode or the show
running-config bgp command in EXEC Privilege mode.
The following example shows how to configure values to reuse or restart a route. In the following example, default = 15 is
the set time before the value decrements, bgp dampening 2 ? is the set re-advertise value, bgp dampening 2 2000 ?
is the suppress value, and bgp dampening 2 2000 3000 ? is the time to suppress a route. Default values are also shown.
Dell(conf-router_bgp)#bgp dampening ?
<1-45> Half-life time for the penalty (default = 15)
route-map Route-map to specify criteria for dampening
<cr>
Dell(conf-router_bgp)#bgp dampening 2 ?
<1-20000> Value to start reusing a route (default = 750)
Dell(conf-router_bgp)#bgp dampening 2 2000 ?
<1-20000> Value to start suppressing a route (default = 2000)
Dell(conf-router_bgp)#bgp dampening 2 2000 3000 ?
<1-255> Maximum duration to suppress a stable route (default = 60)
Dell(conf-router_bgp)#bgp dampening 2 2000 3000 10 ?
route-map Route-map to specify criteria for dampening
<cr>
To view a count of dampened routes, history routes, and penalized routes when you enable route dampening, look at the
seventh line of the show ip bgp summary command output, as shown in the following example (bold).
Dell>show ip bgp summary
BGP router identifier 10.114.8.131, local AS number 65515
BGP table version is 855562, main routing table version 780266
122836 network entrie(s) and 221664 paths using 29697640 bytes of memory
34298 BGP path attribute entrie(s) using 1920688 bytes of memory
29577 BGP AS-PATH entrie(s) using 1384403 bytes of memory
184 BGP community entrie(s) using 7616 bytes of memory
Dampening enabled. 0 history paths, 0 dampened paths, 0 penalized paths
204
Border Gateway Protocol IPv4 (BGPv4)