Where is Howard when we need him! &;-) Seriously, if he were to answer,
I'm sure he would say that your understanding is right on. Routing
protocols are supposed to be ships in the night. So a static route, which
is a different routing protocol (or non-routing protocol), shouldn't affect
OSPF's LSAs. But it does in your case. It could be a bug, as you say.
Do you have a lab where you could try to recreate the problem? I wish I had
more time and I would try it....
Would a workaround be to give the static route a higher administrative
distance? Maybe if you make it a "floating static route" by giving it an
admin distance higher than OSPF, it won't get in the way of Router B's
OSPF's LSA over to Router C. Not sure if that would meet your goals, though.
Priscilla
At 01:15 PM 11/8/00, you wrote:
>This is a resend - apologies if it appears twice. Or indeed three times.
>
>Mark, thanks for your comments.
>A couple of points that I didn't make clear in the first email...
>Although the static route overrides the OSPF route on RTB, RTB does know about
>the 50.0.0.0 network from OSPF as well - it shows up with 'show ip ospf da
>su'.
>So there is an LSA for that network in the OSPF table on RTB.
>My understanding, which you seem to confirm with your point 2, is that routing
>protocols (in this case, OSPF and static routes) work independantly of one
>another, and that barring redistribution, OSPF will not have any knowledge of
>the existence of the static route. If this is the case, then regardless
>of the
>layout of my routers or any other complexities, adding a static route should
>make no difference to what LSAs are distributed by OSPF, and so there
>should be
>no difference in what RTC gets.
>However, these routers seem to think otherwise :-)
>Unfortunately I can't bung on a debug of OSPF to see exactly what LSAs are
>being
>transmitted - I don't think the routers would cope very well and I wouldn't be
>very popular if I brought them down unexpectedly.
>If somebody could confirm or deny my basic understanding of routing protocol
>behaviour, it would be much appreciated, because if I'm wrong I have a lot of
>studying to catch up on...
>RTB is actually an MSM with lots of qualifiers in the IOS version, and RTC
>runs
>a completely different major version of IOS, so it wouldn't surprise me
>too much
>if this is the result of a bug.
>
>JMcL
>
>---------------------- Forwarded by Jenny Mcleod/NSO/CSDA on 07/11/2000
>11:52 am
>---------------------------
>
>
>[EMAIL PROTECTED] on 06/11/2000 05:32:42 pm
>
>Please respond to [EMAIL PROTECTED]
>
>
>To: JENNY MCLEOD/NSO/CSDA@NOTES
>cc: [EMAIL PROTECTED]
> [EMAIL PROTECTED]
>
>
>Subject: Re: OSPF and static routes
>
>
>
>In a message dated 11/6/00 1:12:18 AM Eastern Standard Time,
>[EMAIL PROTECTED] writes:
>
>
> > Had a problem today that doesn't make much sense to me.
> >
> > Very simplified layout (hopefully not oversimplified...)
> >
> > RTA -- RTB -- RTC
> >
> > RTB gets a summary LSA for a network, call it 50.0.0.0, from RTA. This
> > summary
> > LSA is visible with the command 'show ip ospf da su'.
> > There is also a static route for 50.0.0.0 on RTB, with admin distance 1.
> > Not
> > surprisingly, this overrides the OSPF route in RTB's routing table. The
> > static
> > route is NOT redistributed into OSPF.
> >
> > RTB is adjacent with RTC. However the summary LSA for 50.0.0.0 does not
> > get to
> > RTC (as shown by 'show ip ospf da su'), and RTC has no route to
> 50.0.0.0 (as
> > shown by 'show ip ro').
> > If the static route is taken off RTB, OSPF sends the summary LSA to RTC
> > again,
> > and an OSPF route to 50.0.0.0 shows up in RTC's routing table.
> >
> > I was under the impression that routing protocols are generally 'ships in
> > the
> > night' in their operation (in that they each work out what they consider to
> > be
> > the best route, and then the routing process chooses between routing
> > protocols).
> > Why does adding a static route (not redistributed) affect what LSAs OSPF
> > sends?
> > Shouldn't RTC get sent the summary LSA even though RTB has a better static
> > route
> > - how does the OSPF process on RTB even know about the existence of the
> > static
> > route??
> >
________________________
Priscilla Oppenheimer
http://www.priscilla.com
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