02-14-2007 10:22 PM - edited 03-03-2019 03:46 PM
I need some help here as I can't point my finger to the right BGP regexp.
I have multiple upstream, according to the BGP routing table the best path to "AS5" is through upstream "B" (AS2) but I want it to be in upstream "A" (AS1). I'm planning to use local-preference so that it will propagate to all iBGP routers. From provider "A", AS5 is through the following path 1 3 4 5
I'm planning to use route-map in the interface to provider "A"
The configuration look like this;
!
router bgp 100
neighbor ip_address_of_provider_"A" route-map incoming in
!
ip as-path access-list 1 permit ^1_
ip as-path access-list 2 permit ???
!
route-map incoming permit 1
match as-path 1
set local-preference 100
! Here is the route-map for AS5
route-map incoming permit 2
match as-path 2
set local-preference 150
The regexp for AS5 is my problem. I don't want to put 1 3 4 5 as some AS my perform prepending. I also not sure if my route-map will work with two local-preference
Thanks in advance
Solved! Go to Solution.
02-15-2007 03:09 AM
Hi, Medan
Please add one line to end of your route map like this
route-map incoming permit 1
match as-path 1
set local-preference 150
route-map incoming permit 2
This will make other routes not be filtered.
HTH
SSLIN
02-15-2007 02:17 AM
Hi medan
If you are going to apply the route map on link to the provider A, since all the routes advertised by A(AS1) will always have as-path attribute beginning with 1, all routes will be permited by this route map, making the policy useless.What you should do is to match the routes with as-path attribute ending with 5. So change your as-path list as follows
ip as-path access-list 1 permit _5$
and set local-preference to 150 to the routes which match the above as-path list.This should make all paths to AS 5 prefer the way through provider A.
I can't understand what's your intention on the second as-path list.
HTH
SSLIN
02-15-2007 02:32 AM
Hi SSLIN,
Thank you for your reply.
Ignore the second as-path list. Its for the AS5, I put ??? because I can't figure out the regexp :)
So that means I will have the following;
!
router bgp 100
neighbor ip_address_of_provider_"A" route-map incoming in
!
ip as-path access-list 1 permit _5$
!
route-map incoming permit 1
match as-path 1
set local-preference 150
But this affects all other routes coming from AS1. From 200k prefixes, it goes down to 80 prefixes.
02-15-2007 03:09 AM
Hi, Medan
Please add one line to end of your route map like this
route-map incoming permit 1
match as-path 1
set local-preference 150
route-map incoming permit 2
This will make other routes not be filtered.
HTH
SSLIN
02-15-2007 03:21 AM
Hi SSLIN,
It works!
Thank you :)
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