From: Rajib Khan (rajib56666@yahoo.com)
Date: Thu Jun 30 2005 - 15:19:50 GMT-3
Hi Guys,
During the exam normally it states on the first page that " if you have to configure an additional interface then use ip add from the main range" bearing this in mind will cisco except "ip unnumbered" under tunnel interface
Thanks
Raj
ccie2be <ccie2be@nyc.rr.com> wrote:
Hi Tom,
Thank you.
Thanks for confirming this for me. At the moment I don't have gear to lab
this up and verify and then I start to doubt myself.
I'm also glad I don't have to be concerned with 12.3T train just yet.
Tim
-----Original Message-----
From: Tom Lijnse [mailto:Tom.Lijnse@globalknowledge.nl]
Sent: Thursday, June 30, 2005 10:51 AM
To: Scott Morris; ccie2be; Schulz, Dave; Larry Roberts; Gustavo Novais
Cc: ccielab@groupstudy.com
Subject: RE: OSPF Virtual Link and GRE tunnel.
Hi Tim,
As Scott points out here the main issue is that an unnumbered interface
will inherit the area of the interface that it points to. (Since it does
not have an IP address of its own it will check the OSPF network
statements against the interface that it is pointing to).
So you need to find an interface in area 0 on both routers to be able to
build an unnumbered tunnel that is part of area 0 (which in your
scenario is not possible).
As of IOS 12.3(11)T there is a solution to this problem:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft
/120limit/120s/120s29/ospfarea.htm
This new feature allows you to explicitly assign an interface (numbered
or unnumbered) to an area by use of the interface level command 'ip ospf
area '.
This is 12.3T though, so for the lab this is not a feasible solution
yet.
Regards,
Tom Lijnse
CCIE #11031
Global Knowledge
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Scott Morris
Sent: donderdag 30 juni 2005 16:24
To: 'ccie2be'; 'Schulz, Dave'; 'Larry Roberts'; 'Gustavo Novais'
Cc: ccielab@groupstudy.com
Subject: RE: OSPF Virtual Link and GRE tunnel.
Well.... Wieth an unnumbered interface you can match to whatever
interface
you want to. The problem becomes, logically you would choose the
outbound
(ethernet) interface. But you're trying to put the same thing into two
areas now.
Try it out! See what festive things the router tells you!
Scott
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: Thursday, June 30, 2005 10:16 AM
To: swm@emanon.com; 'Schulz, Dave'; 'Larry Roberts'; 'Gustavo Novais'
Cc: ccielab@groupstudy.com
Subject: RE: OSPF Virtual Link and GRE tunnel.
Scott,
As usual, you are absolutely right - I was mixing up 2 different issues.
Let me rephrase.
Let's say I need a gre tunnel (the transit area is a stub of some sort)
BUT
I'm not allowed to add any ip addresses.
area 1 R1 area 2 R2 area 0
.1 2.0.0.0/24 .2
R1 has 2 interfaces, E1 and E2, where E1 is in area 1 and E2 is in area
2
and no other interfaces.
R1's config:
int tun 1
ip address unnumbered ????
tun source int e1
tun destination 2.0.0.2
router ospf 1
net 2.0.0.0 0.0.0.255 area 2
net ????? area 0
Assuming this can be done, what should ?????? be?
TIA, Tim
-----Original Message-----
From: Scott Morris [mailto:swm@emanon.com]
Sent: Thursday, June 30, 2005 9:47 AM
To: 'ccie2be'; 'Schulz, Dave'; 'Larry Roberts'; 'Gustavo Novais'
Cc: ccielab@groupstudy.com
Subject: RE: OSPF Virtual Link and GRE tunnel.
I think you're confusing two issues. A GRE tunnel is NOT a virtual
link.
It's a virtual/logical interface used to connect things together.
A virtual link will ALWAYS be established between the router-id's of two
ABRs. A tunnel interface may internally use "ip unnumbered" but don't
always expect to bring up an OSPF neighbor relationship! While the OSPF
spec does allow P2P links to not share the same subnet mask, you still
must
match SOME things (like area ID) in order to bring a neighbor up!
HTH,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Thursday, June 30, 2005 9:28 AM
To: 'Schulz, Dave'; 'Larry Roberts'; 'Gustavo Novais'
Cc: ccielab@groupstudy.com
Subject: RE: OSPF Virtual Link and GRE tunnel.
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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