From: Petr Lapukhov (petr@internetworkexpert.com)
Date: Wed Jul 05 2006 - 02:54:43 ART
So just to summarize what's been said, the techniques we may use
to filter *External* routing information with OSPF:
1) Local router
1.1) distribute-list (per-interface, based on prefixes),
1.2) distribute-list with route-map ( match next-hop, tag, interface).
Match next-hop didn't work with prefix-list though, just with
ACL
1.3) Change cost/bandwidth in any way
2) Transit router, non-ABR
2.1) Change cost/bandwidth in any way
2.2) Max-metric lsa (similar to above)
3) Transit router, ABR
3.1) With NSSA "summary not-advertise", or change RID
to influence translator election
3.1) Change cost/bandwidth in any way
3.3) Filter forward-address with NSSA and other cases,
where FA is present (also, nssa suppress-fa may help here)
There are also a number of ways to use virtual links to influence routing
decision, but this is getting complex already :)
I can drop few examples a bit later, just too loaded with work now :(
HTH
-- Petr Lapukhov, CCIE #16379 petr@internetworkexpert.comInternetwork Expert, Inc. http://www.InternetworkExpert.com Toll Free: 877-224-8987 Outside US: 775-826-4344 2006/7/4, D.H. Williams <draythw@gmail.com>: > > :) I could say I was kidding, but alas, I was being serious. Sometimes > I > don't think before I type, nevermind ... > > On 7/4/06, Narbik Kocharians <narbikk@gmail.com> wrote: > > > > Unbelievable > > > > On 7/4/06, Petr Lapukhov <petr@internetworkexpert.com> wrote: > > > > > Forgot to mention, > > > > this feature is particularly useful in case where you have > > shared interface with multiple neighbors. In other cases > > you may stick with basic distribute-list functionality. > > > > HTH > > > > 2006/7/4, Petr Lapukhov <petr@internetworkexpert.com>: > > > > > > Just a quick note here, > > > > > > you may also opt to use "distribute-list with route-map" at R3, > > > to filter inbound routes based on next-hop value (or output > interface), > > > directly at "receiving" router. > > > > > > > http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120limit/120s/120s24/routmap.htm > > > > > > > > > > > filtering with distance won't work here, since external routes all > have > > > the same > > > advertising RID (route-source). > > > > > > Everything else should probably use "database-filter" or cost > > manipulation > > > in some > > > way (max-metric falls under that category too), to adjust > > forward-metric. > > > > > > HTH > > > > > > -- > > > Petr Lapukhov, CCIE #16379 > > > petr@internetworkexpert.com > > > > > > Internetwork Expert, Inc. > > > http://www.InternetworkExpert.com <http://www.internetworkexpert.com/> > > > Toll Free: 877-224-8987 > > > Outside US: 775-826-4344 > > > > > > 2006/7/4, D.H. Williams <draythw@gmail.com>: > > > > > > > Hey fellows, > > > > > > > > All right, was tinkering with OSPF filtering last night, and got a > few > > > > > > questions and what have not I wanted to ask, to see what everyone > has > > to > > > > say. Consider the following situation: > > > > > > > > R5 with two point-to-point subinterfaces going to R1 and R2. > > > > > > > > R1 and R2 have hdlc connections up to R3. > > > > > > > > All of the above links are running OSPF; backend of R5 is running > > RIP; > > > > Mutual Redistribution on R5. > > > > > > > > Now, let's say I want the following scenerio, I want R3 to get to > all > > > > the > > > > RIP routes (E2) via R1. I tried the distribute-list statement on R2 > > > > using > > > > teh route-map, but this just affects the route table, not the ospf > > > > database, > > > > so r2 still advertise the E2 routes up to R3, even though they > aren't > > in > > > > his > > > > routing table. > > > > > > > > My question, how can I affect R3 to where it prefers R1, including > not > > > > > > seeing anything advertise from R2 in the routing table? I'd also > like > > > > R2 to > > > > route through R3 to get to Rip routes. And i'm looking for a > solution > > > > that > > > > doesn't use cost or bandwidth (too easy and obvious, you know). > > > > > > > > Thanks in advance! > > > > D > > > > > > > > > > _______________________________________________________________________ > > > > Subscription information may be found at: > > > > http://www.groupstudy.com/list/CCIELab.html > > > > > > > > > > > > > > > > > > > > > > > > > -- > > Petr Lapukhov, CCIE #16379 > > petr@internetworkexpert.com > > > > Internetwork Expert, Inc. > > http://www.InternetworkExpert.com <http://www.internetworkexpert.com/> > > Toll Free: 877-224-8987 > > Outside US: 775-826-4344 > > > > _______________________________________________________________________ > > > > Subscription information may be found at: > > http://www.groupstudy.com/list/CCIELab.html > > _______________________________________________________________________ > Subscription information may be found at: > http://www.groupstudy.com/list/CCIELab.html
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