North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: Cisco Route filtering [was Re: OPS: BGP spew from ASN 7374]
> > Let's assume for a moment that I have a network of 209.123/18 > > (1/4 of a > > classful B). > > > > Let's further assume that my upstream filters me with: > > > > access-list 2002 permit ip host 209.123.0.0 host 255.255.0.0 > > neigh 2.3.4.5 distrib 2002 in > > > > Will my /18 announcement make it through this /16 filter? > > > No. The ACL specifies an exact match. You should change 'host 255.255.0.0' to '255.255.0.0 0.0.255.255' to allow any _more specific_ mask. Read CISCO docs. > > > Would the same be true with a prefix-length filter, which I assume the > > syntax would be: > > > > ip prefix-list 1 permit 209.123.0.0/16 > > neigh 2.3.4.5 prefix-list 1 in > > > > Same deal. > > Chris > > Aleksei Roudnev, Network Operations Center, Relcom, Moscow (+7 095) 194-19-95 (Network Operations Center Hot Line),(+7 095) 230-41-41, N 13729 (pager) (+7 095) 196-72-12 (Support), (+7 095) 194-33-28 (Fax)
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