[c-nsp] OSPF NSSA Question
dan at beanfield.com
Mon Oct 4 09:52:37 EDT 2004
Again, thanks to all who have replied, this discussion is invalueable to me.
I spent much of the night re-implementing my design with EIGRP.
It's stub behaviour is much more like I expect....
ip summary-address eigrp 100 0.0.0.0 0.0.0.0 5
On each interface of the 6509 facing an access router to advertise the default
route down. Each access router is setup:
T1C-2.902.1iw2#sh run | beg eigrp 100
router eigrp 100
network <blahh> 0.0.0.0
eigrp stub connected static summary
no eigrp log-neighbor-changes
I am redistributing static/connected (with appropriate route maps of course)
to get the customer routes into EIGRP, and routes from access router 1 do NOT
show up in access router 2. Perfect!
However I have run into a little gotcha.... I sort of oversimplified my
design a bit for clarity. Each 3550 is actually hung off of 2 6509s. Each
GigE link spans the two 6509s, and goes through a 3550. My problem now, is
that there appears to be no way to stop the 6509s from neighbouring with each
other over the gig links (of which there could be a hundred or so)....
I could bump up the costs, but it would be nice if there was a clean way to
tell EIGRP to "F-Off don't neighbour with this guy"...
After some sleep tonight, I may re-implement it again with RRs & BGP to see
how that works out.
On Monday 04 October 2004 02:44, Jay Hennigan wrote:
> > I don't think you can apply a distribute-list against an OSPF neighbor,
> > can you? This would violate the technical requirements for OSPF
> > operation.
> > I thought that one could only apply distribute-lists against
> > redistributed protocols.
> You can filter OSPF inbound since 12.2(28)S and 12.2(15)T
>de09186a008012db77.html (watch wrap) or http://tinyurl.com/5gw8v
> There is a distinction between the LSA database which must comply with
> the OSPF technical requirements and the IP routing table which does not
> need to match the LSA database. The URL above addresses that.
> " Users can define a route map to prevent OSPF routes from being
> added to the routing table. This filtering happens at the moment
> when OSPF is installing the route in the routing table. This feature
> has no effect on LSA flooding. In the route map, the user can match
> on any attribute of the OSPF route. "
> So, it looks like indeed, on his access routers, he can if he chooses
> filter all but the default route from OSPF from getting into the routing
> table. So the answer to the original question is yes, you can prevent
> the customer routes from other routers in your area from showing up in
> the routing table of every access router. Seeing as those customer routes
> will all have the same next-hop of the distribution router anyway
> (different VLANs from each access router back to distribution), doing this
> shouldn't blackhole one customer from reaching another.
> Whether having 100 access routers and the distribution router all in one
> area or splitting them up is a better design, or whether OSPF is even
> the appropriate protocol for this application are still open to debate.
> Jay Hennigan - CCIE #7880 - Network Administration - jay at west.net
> WestNet: Connecting you to the planet. 805 884-6323 WB6RDV
> NetLojix Communications, Inc. - http://www.netlojix.com/
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