02-28-2008 02:19 PM - edited 03-03-2019 08:54 PM
Hi everyone not sure if this is the right place to put this but I have a BGP statement that I'm trying to understand..it is as follows:
neighbor VNET filter-list 17 out
ip as-path access-list 17 permit ^[0-9]+$
ip as-path access-list 17 permit ^$
what is this trying to tell me?
Solved! Go to Solution.
02-28-2008 03:09 PM
The ngihbor filter list command is used to filter BGP routes based on AS-Path access list. As-path access list uses regular expression to match BGP as-path.
In regular expression, ^ mathces the beginning of a string, $ matches end, + matches the preceding element 1 or more times. See
http://en.wikipedia.org/wiki/Regular_expression
ip as-path access-list 17 permit ^[0-9]+$ would therefore match a string of digits. This means an as path with a length of 1.
ip as-path access-list 17 permit ^$ would match a null string. This would mean no as-path or locally originated routes.
As the filter-list is applied outbound, only locally originated routes and routes with an as-path length of 1 would be advertised out.
See
02-28-2008 02:51 PM
Hi,
I guess you have peer groups here, since you have a peer name.
it will try to tell you that you should only allow (locally originated routes) and updates from any AS number matches 0 or 1 time.
HTH
Mohamed
02-28-2008 03:09 PM
The ngihbor filter list command is used to filter BGP routes based on AS-Path access list. As-path access list uses regular expression to match BGP as-path.
In regular expression, ^ mathces the beginning of a string, $ matches end, + matches the preceding element 1 or more times. See
http://en.wikipedia.org/wiki/Regular_expression
ip as-path access-list 17 permit ^[0-9]+$ would therefore match a string of digits. This means an as path with a length of 1.
ip as-path access-list 17 permit ^$ would match a null string. This would mean no as-path or locally originated routes.
As the filter-list is applied outbound, only locally originated routes and routes with an as-path length of 1 would be advertised out.
See
02-28-2008 03:28 PM
Hi,
The Original poster has a bgp name as neighbor which defined for peer groups:
Pls check bellow:
neighbor ((VNET)) filter-list 17 out
HTH
Mohamed
02-28-2008 04:38 PM
Thank you everyone for replying I will finish looking at those links
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide