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New Member

Reconfiguring Layer 3 to be layer 2 PtP

Hello all,

This is a little strange for me as this is the first time I am ever using this forum. Please be patient as I try to describe my issue.

This week we have began a major network reconfiguration, not by our choice. We have been forced by the state to change over our network.

Anyway, the folks doing this reconfigure know less than what I do, which is scary.

Anyway, here is the situation. Currently we have a point to point t-1 between 2 buildings and 2 T-1's out to the internet. I have a 1721 and 2614 connecting our PtoP and a 26XX connecting us to the internet.

In this reconfiguration we are getting 6 t1's at one site and 1 t-1 at the remote site. They all dead-end at the same location, only 1.5 MB is dedicated for the Point to Point link.

Well, they are giving me an Ethernet port off the router specifically for that traffic at each end. Now, they want me to purchase 2 additional Ethernet WIC for my routers so that I can route traffic from point to point.

I shared with them, why don't they just tunnel between the two IP addresses of the Point to Point WAN link and be done with it. That way I can totally elimate BOTH routers and use my main router, a 4006 with a router blade, create another VLAN, and provide all the VTP, DHCP, Multicast, etc, all in one place. (I may keep the 1721 in the remote location just for multicast).

Now, I remember this briefly from CCNP class but never did it. Something about EGR, Source and destination.

I have a consultant kinda working on this, however, I would like to see IF I can figure it out first.

Any help anyone?

Sincerely,

Tom Hafemann

3 REPLIES
Purple

Re: Reconfiguring Layer 3 to be layer 2 PtP

Hi Tom,

I'm afraid I'm having trouble visualing your setup. Would it be possible for you to attach a diagram showing your current setup and also the proposed one ?

Thanks,

Paresh

New Member

Re: Reconfiguring Layer 3 to be layer 2 PtP

Maybe this will help a little more.

I am trying to create a GRE tunnel between to points that will do layer 2 instead of Layer 3.

Tom

Purple

Re: Reconfiguring Layer 3 to be layer 2 PtP

Hi Tom,

You can't really do L2 switching over a GRE tunnel. However, you can make multiple IP hops appear to be a single hop.

I've included an example below (there could be multiple IP hops between the 2 routers):

Router A

=========

interface tunnel 0

ip address 192.168.1.1 255.255.255.252

tunnel source 10.1.1.1

tunnel destination 10.100.99.1

!

interface serial 0

ip address 10.1.1.1 255.255.255.0

Router A

=========

interface tunnel 0

ip address 192.168.1.2 255.255.255.252

tunnel source 10.100.99.1

tunnel destination 10.1.1.1

!

interface serial 0

ip address 10.100.99.1 255.255.255.0

Hope that helps - pls rate the post if it does.

Paresh

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