RE: OSPF ON GRE Tunnel

From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Fri Mar 26 2004 - 17:26:54 GMT-3


        A GRE tunnel can run as unnumbered. However, the important question
is what are you unnumbering it to? If you unnumber it to an interface
that's already covered by an OSPF network statement, the tunnel will inherit
that OSPF configuration.

HTH,

Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com

Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Scott, Tyson C
> Sent: Friday, March 26, 2004 1:06 PM
> To: Edwards, Andrew M; christopher snow; Ashok Verma (ashoverm)
> Cc: ccielab@groupstudy.com
> Subject: RE: OSPF ON GRE Tunnel
>
> Will an IP unnumbered interface work? I don't think it does. I believe
> you need to have an IP address on the interface for OSPF. I had the
> following scenario on a practice lab I did. I did the scenario twice.
> I believed it worked in the newer code but I could not get the RIP
> routes that router4 new about to SW1. I had other RIP routes coming to
> router3 from another router that SW1 would learn but not the routes from
> R4 RIP. This is another subject though.
> My main point is that in either situation, with the two codes I
> tried it on (12.2(2)T and 12.2(15)T), the GRE tunnel would not work
> unless it had an IP address.
> It is my understanding that unless the test states not to add IP
> addresses and interfaces to a router you can do it. But if in doubt ask
> the proctor with a statement of what you are looking to do and that it
> doesn't state not to can you do it.
>
> R5___
> |
> FRAME HUB & SPOKE
> OSPF AREA0------R3____OTHER IGP
> ___|
> __R4___
> | |
> RIP OSPF STUB
> BB2_| |_SW1____Area0
>
> Regards,
>
> Tyson Scott
> Agilent Problem Management Team
> Managed Network Services
> Phone: 313-583-5812
> Pager: 877-997-0811
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Edwards, Andrew M
> Sent: Friday, March 26, 2004 12:00 PM
> To: christopher snow; Ashok Verma (ashoverm)
> Cc: ccielab@groupstudy.com
> Subject: RE: OSPF ON GRE Tunnel
>
> Effectively building a tunnel and putting it into the backbone of area 0
> is what a virtual-link does... So you are just going to need to build
> your own virtual link 8)
>
> -----Original Message-----
> From: christopher snow [mailto:cbsnow31@yahoo.com]
> Sent: Friday, March 26, 2004 5:52 AM
> To: Ashok Verma (ashoverm)
> Cc: ccielab@groupstudy.com
> Subject: Re: OSPF ON GRE Tunnel
>
>
> Do an ipunnumbered of an interface that is already in area 0.
>
> Chris
>
>
>
> "Ashok Verma (ashoverm)" <ashoverm@cisco.com> wrote:
> Hi all
>
> For all OSPF gurus.....here is a very good query....
>
> R1--------R2-----R3
>
> Between R2 and R3 ospf area 0 is running, and between R1 and R2 area 3,
>
> On R1 I have a loopback address ( 1.1.1.1) and my requirement is to put
> it in area 1. And I should not be using the virtual link. I should have
> 1.1.1.1 in R3's routing table.Is any way to do it .
>
> As per my views, there are two ways .....
>
> Solution 1: Use Tunnel between R2 and R1 and then assign the tunnel IP
> in ospf area 0 ...........But the question is In real lab we are not
> allowed to use any extra ip....so can we still use this solution using
> the IP unnumberd.( in that case what ip we should be putting in area 0
> ??)
>
> Solution 2: Use multiple process on R1 and then redistribute them .But
> again question is are we allowed to use multiple process ids in ospf.
>
> Which solution look better from the real lab point of view.
>
>
> Regards.
>
> Ashok Kumar Verma
> CCIP,CCDP,CCNP
> Network Consulting Engineer
> Customer Advocacy Advanced Service Dep.
> Service Provider AS Div.2
> Cisco Systems, K.K.Japan.
>
> Tel: +81-3-5324-4583
> e-mail: ashoverm@cisco.com
>
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