From: ccie2be (ccie2be@nyc.rr.com)
Date: Thu Jun 30 2005 - 10:28:12 GMT-3
Dave,
Is there a problem with using ip unnumbered for the virtual link?
The issue I'm thinking about here is suppose one of the virtual-link
endpoints doesn't have an interface in area 0 to reference. Won't that be a
problem?
Or, is the virtual-link still in area 0 even if one of the endpoints using
ip unnumbered references an interface which is in a non-backbone area?
TIA, Tim
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Schulz, Dave
Sent: Thursday, June 30, 2005 7:20 AM
To: Larry Roberts; Gustavo Novais
Cc: ccielab@groupstudy.com
Subject: RE: OSPF Virtual Link and GRE tunnel.
If you are addressing the interfaces at both ends of your tunnel and
putting them in area 0, then you are not violating OSPF. You have to
remember to do it on both ends of the tunnels (R2 and R7, R2 and R7, R2
and R9). In this way, you are truly extending OSPF area 0. Hope this
helps.
Dave
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Larry Roberts
Sent: Thursday, June 30, 2005 12:28 AM
To: Gustavo Novais
Cc: ccielab@groupstudy.com
Subject: Re: OSPF Virtual Link and GRE tunnel.
Somebody please correct me if Im wrong on my understanding of
Virtual-links, but I believe the virtual link configuration mentioned
below is invalid.
I was under the understanding that Virtual links require that one router
be an ABR to area 0 (R2). This virtual link provides backbone
connectivity to area 0 for the ABR (R5) but it doesn't *extend* the
backbone to R5 ( R5 doesn't have an interface in Area 0). When you
create your second virtual link from R5 to R7, neither of these routers
have an interface in Area 0.
If you do a "show ip ospf interface" on R5, you will see that none of
the interfaces are listed as in area 0. While this configuration seems
to work fine, It appears to me that it is in violation of OSPF
configuration guidelines.
Can anyone correct my understanding on this?
Gustavo Novais wrote:
> Apparently I had a dumb config problem on R7... Duhhh... It's working
> now.
> Either way, any way how to solve recursive routing situation I
> presented?
> Thanks
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Gustavo Novais
> Sent: quarta-feira, 29 de Junho de 2005 19:33
> To: ccielab@groupstudy.com
> Subject: OSPF Virtual Link and GRE tunnel.
>
> Hello group
>
> I have a topology like this.
>
> Area0--(R2)---Area25---(R5)---Area57----(R7)----Area78----(R9)
>
> It showed up on a exercise in order to test Virtual-links etc.
> I did it using vlink between R5 and R2 for area 57 reachability and a
> vlink between R7 and R5 for area 78 reachability.
>
> But I'd like to try the same topology using GRE tunnel between R7 and
> R2.
> If I extend Area 0 onto interface tunnel on R7, I get recursive
routing
> and the tunnel goes down. (OSPF will prefer intra area routes vs extra
> area routes, so the preferred path to the tunnel destination is
through
> the tunnel itself, which shuts it down.
>
> If I extend area 78 to R2 Tunnel, apparently all is well, but the
> problem is that R5 starts complaining that Received invalid packet:
> mismatch area ID, from backbone area must be virtual-link but not
found
> from 150.50.57.7, Ethernet0/0, even now that area 78 is connected
> directly to area 0, and area 57 still has its vlink on R5 to Area 0.
>
> Any ideas why is the router R5 showing this behaviour? Any suggestions
> how to correct it?
>
> Thanks
>
>
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