Concept Guide

● View all flap statistics or for specific routes meeting the following criteria.
EXEC or EXEC Privilege mode
show ip bgp [vrf vrf-name] 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 in Dell EMC Networking OS 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.
DellEMC(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>
DellEMC(conf-router_bgp)#bgp dampening 2 ?
<1-20000> Value to start reusing a route (default = 750)
DellEMC(conf-router_bgp)#bgp dampening 2 2000 ?
<1-20000> Value to start suppressing a route (default = 2000)
DellEMC(conf-router_bgp)#bgp dampening 2 2000 3000 ?
<1-255> Maximum duration to suppress a stable route (default = 60)
DellEMC(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).
DellEMC>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
Neighbor AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.114.8.34 18508 82883 79977 780266 0 2 00:38:51 118904
10.114.8.33 18508 117265 25069 780266 0 20 00:38:50 102759
DellEMC>
To view which routes are dampened (non-active), use the show ip bgp dampened-routes command in EXEC Privilege
mode.
Border Gateway Protocol (BGP)
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