From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Sun Jun 26 2005 - 23:07:32 GMT-3
Two points to be sure of.
First the tunnel source must be reachable prior to the tunnel going up
and the far end must not know about this address via OSPF over the
tunnel (distance or filtering can be used to ensure this). The same is
true of the tunnel destination.
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Sila Moni
Sent: Sunday, June 26, 2005 8:56 PM
To: George Cassels; 'ccie2be'; 'Group Study'
Subject: RE: using nssa and area X range together
Thanks George. I was like 'oopsie' when I saw it. :)
So in this case R2 is an ASBR since it connects to external net. That
explains why you used summary-address. Now that you got me thinking,
I've one question involving GRE (expanding upon Tim's topology a bit).
R4 (area 2) R1 (nssa area 1) R2 (area 0) R3
We have a disconnected area 2 separated by nssa. In this case, you'd
need to create a GRE tunnel. When I last try to lab it out, I'd
recursive route problem when I used ip unnumber.
a) How do I avoid recurvise route?
b) Replace area 2 with area 0. Do you still configure the tunnel the
same way?
TIA,
Sila
--- George Cassels <glcassels3@nc.rr.com> wrote:
> Sila,
>
> Take a look at my response to Tim...I used the summary-address
> command and it aggregated the routes going to another ospf area 0
> router.
>
> George
>
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of Sila Moni
> Sent: Sunday, June 26, 2005 7:31 PM
> To: ccie2be; Group Study
> Subject: Re: using nssa and area X range together
>
> You can't summarize external routes (I don't have a rack to lab it out
> to confirm). Since R2 has only one exit point, you can use LSA 3
> filter to deny all routes except for the default prefix. Example:
>
> ip prefix-list LSA-FILTER deny x.x.x.x/24 ip prefix-list LSA-FILTER
> permit 0.0.0.0/0 le 32 !
> router ospf 1
> area 1 filter-list prefix LSA-FILTER in
>
>
> --- ccie2be <ccie2be@nyc.rr.com> wrote:
>
> > Hi guys,
> >
> > This is an interesting scenario - at least I
> hadn't
> > thought much about this
> > previously.
> >
> > Let's say you have this topology:
> >
> > IGP R1 nssa R2 area 0 R3
> >
> >
> > R1 is redist routes from another IGP into OSPF.
> Can
> > I use the area X range
> > command on R2 to summarize routes learned from the IGP redist into
> > the nssa area so that the backbone doesn't have all those specific
> > routes from the other routing protocol?
> >
> >
> > And, more generally, do I need to be concerned
> about
> > any restrictions on
> > using the area X range command to summarize routes
> > into the backbone area
> > depending upon what type of stub area is
> configured?
> >
> > What I find interesting about this scenario is
> that
> > typically when I think
> > about what type of stub area to configure, I'm
> > concerned about what routes
> > are advertised into the stub area from the
> backbone.
> >
> > In this scenario, it's just the opposite. Here
> the
> > concern is what routes
> > area advertised from the stub area into the
> backbone
> > area.
> >
> > (I don't have access to any routers at the moment
> to
> > lab this up.
> >
> > TIA, Tim
> >
> >
>
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