[c-nsp] command that can display the dropped routes containing AS loops

Song Li refresh.lsong at gmail.com
Mon Jan 12 20:48:49 EST 2015



on juniper router, I know a command can do that:

show route hidden aspath-regex .*<Target-AS>.*

It seems that there is no similar command on a cisco router.


在 2015/1/13 1:30, b.turnbow at twt.it 写道:
> Hi,
>> On Mon, 2015-01-12 at 22:17 +0800, Song Li wrote:
>>> I am curious about the AS loops in the AS-path. I think there should
>>> be a very, very few received BGP routes that contain the local AS#.
>>> But because such routes will be dropped and not installed in Loc-RIB,
>>> I want to know if there is a command that can display the dropped
>>> routes containing AS loops on cisco. Does anybody know?
>> If you have "soft-reconfiguration inbound" configured on the neighbor you
>> could probably use:
>>    show ip bgp neighbor received-routes | incl _64512_
>> where 65412 is you own AS. You would need soft-reconfiguration since it
>> would otherwise not make it into the BGP table. Keep in mind the risks
>> regarding memory when enabling it. And the above command might be
>> rather slow since it has to process the whole table as text.
>> I don't know of any other way though.
> Or you could accept them in  with allow as in /accept own  being very very careful not to create havoc on your network... :-)
> Try and see about debugging bgp , be careful about resources ,   I seem to remember  that debugging  bgp events having an error message being logged when own as is found in updates.
> Brian

Song Li
Room 4-204, FIT Building,
Network Security,
Department of Electronic Engineering,
Tsinghua University, Beijing 100084, China
Tel:( +86) 010-62446440
E-mail: refresh.lsong at gmail.com

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