North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: AS prepending
Update 2: More info. When I have tested the failover by pulling the plug on the preferred ISP, I do not see my network in looking glass. Secondly, the backup provider has told me the the route is not in the (rib). Philip --- Mark Kasten <[email protected]> wrote: > <offlist> > > fwiw, it's in the routing table (rib), not their > forwarding table (fib). > if they look on their side of the session, they > will have the prefix > in "show ip bgp" or "show route", but it will not > propogate beyond that > router because their network prefers the other path > with the short AS. > a router doesn't forward all rib entries, only fib > entries. > > > for example: > > dcr4.nyr> show route 141.77.0.0/16 > 141.77.0.0/16 *[BGP/170] 3w4d 01:53:30, MED 98, > localpref 100, from > 206.24.194.105 > AS path: 1273 ? > > via so-0/0/0.1510 > via so-1/1/0.10 > [BGP/170] 9w3d 12:26:09, MED > 128, localpref 80 > AS path: 3356 1273 I > > to 4.68.127.205 via > so-6/1/0.0 > [BGP/170] 21:32:50, MED 128, > localpref 80 > AS path: 1239 1273 ? > > to 144.232.9.117 via > so-3/1/0.0 > > > on a router, one hop away: > > > kar1.nyr> show route 141.77.0.0/16 > > inet.0: 173067 destinations, 345433 routes (172951 > active, 0 holddown, > 547 hidden) > Restart Complete > + = Active Route, - = Last Active, * = Both > > 141.77.0.0/16 *[BGP/170] 3w4d 01:53:59, MED 98, > localpref 100, from > 206.24.194.105 > AS path: 1273 ? > > to 208.174.228.1 via ae0.0 > > > > no evidence of the 3356_1273 or the 1239_1273 path. > if i lose the > direct 1273 path, then one of those paths would then > be propogated as > the preferred path. > > > hth's. > > mark > > > Philip Lavine wrote: > > > Update: > > > > I am prepending my AS 3 times to the un-preferred > ISP. > > Both ISP's are my peers. The un-preferred ISP > claims > > the see my advertisement yet they do not add it to > > their routing table (suggests filtering??). They > claim > > all the filtering they are doing is based on the > > networks I told them over the phone that I was > using > > with that AS. > > > > Philip > > > > --- Jon Lewis <[email protected]> wrote: > > > >>On Fri, 8 Apr 2005, Philip Lavine wrote: > >> > >> > >>>I am using AS prepending to favor one ISP over > >>>another, in a BGP multihomed/multiISP scenario. > >> > >>Why > >> > >>>does the ISP receiving the prepends fail to add > my > >>>network into their routing table? Is this a > >> > >>"feature" > >> > >>>of BGP, or have I gone too far with 3 prepend > >>>statements. > >> > >>Who's ASN are you prepending on your advertised > >>routes? > >> > >> > > > > > ---------------------------------------------------------------------- > > > >> Jon Lewis | I route > >> Senior Network Engineer | therefore you are > >> Atlantic Net | > >>_________ http://www.lewis.org/~jlewis/pgp for PGP > >>public key_________ > >> > > > > > > __________________________________________________ > > Do You Yahoo!? > > Tired of spam? Yahoo! Mail has the best spam > protection around > > http://mail.yahoo.com > __________________________________ Do you Yahoo!? Yahoo! Mail - 250MB free storage. Do more. Manage less. http://info.mail.yahoo.com/mail_250
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