I'm having trouble with this AS-Path situation. I have 2 routers (A and B)
running iBGP to each other.
Each router has a single eBGP connection to a different service provider.
ISP-A ISP-B
| |
A-------B
>From ISP A I am receiving partial routes, basically network within its AS.
>From ISP B I am receiving full internet routes.
Here is the problem: The partial routes from ISP A are summarized, and the
routes from ISP may not be summarized. So my router A has an entry for
12.0.0.0/8 and the AS path has 1 entry. Router B
receives the 12.0.0.0/8 through iBGP and also more specific routes from
ISP-B (12.20.1.0/24, 12.96.0.0/16). In router B the 12.X.X.X BGP entries
have the ISP-A AS# as the first entry in the AS-Path.
Router B, because of the longest match rule, prefers the Router B-->ISP B
path for the more specific networks.
I would like to use IP as-path filters to filter incoming updates from ISP-B
so not to learn networks originating from ISP-A AS#.
What is the regular expression to do this??
ip as-path access-list 20 deny ?????? ^as#_ _as#$
>From sho ip bgp
Network Next Hop
*> 12.0.0.0 A.A.A.A NEIGHBOR
*> 12.0.48.0/20 B.B.B.B NEIGHBOR
*> 12.0.252.0/23 B.B.B.B NEIGHBOR
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=16068&t=16068
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