On Tue, 5 Dec 2000, John Neiberger wrote:
> I'm in a multihoming situation where, so far, one provider is telling me
> they can only send the full routing table without some special arrangements.
> This sounds like a load of bullhockey, but that's what they're saying. So,
> here's the question...
>
> I only want to receive from both ISPs their routes and their customer
> routes. Then, I'll have a default route to the better ISP with a backup
> default to the second ISP.
>
> Is there a way to filter out the routes I don't want using regular
> expressions? I couldn't figure out how to accept an ISP's routes plus their
> customer routes while not accepting everything else. One ISP tags those
> routes allowing me to filter by community attribute, but the other is
> playing dumb. (The dumb one is Sprint, and it seems they are being a pain
> just because they can.)
Ok, well lets say your upstream is AS 666, the devil himself.
neighbor x.x.x.x filter-list 51 in
ip as-path access-list 51 permit ^666 ?[0-9]*$
this would allow all routes with just "666" in the AS PATH, and
additionally one more hop. Customers of 666 who prepend could get
"missed" by this.........but all and all its a good compromise. BGP's
regex's dont' support forward look-ahead type matching (at least I don't
think so) so you can't really say "And also count additional hops as long
as they are the same as the previous hop" (for prepending customers).
>
> It's late, my brain is toast, and I'm tired of thinking about it. Regular
> expressions give me a headeache, anyway. Any ideas on how to do this?
>
> Many thanks as always,
> John
>
>
>
>
>
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-----------------------------------------------
Brian Feeny, CCNP+ATM, CCDP [EMAIL PROTECTED]
Network Administrator
ShreveNet Inc. (ASN 11881)
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