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New Member

Will this work?

I am redoing our network design for existing offices on our new MPLS circuit. Will the remote offices workstations, servers, and phones be able to communicate with this topology?

I was thinking that the local PC's, etc would think that since a request for another offices PC may think it's on the same network, it would not request to the router. I am guessing IP PROXY-ARP would be required? If so, will it definately work? What interfaces would I need to place it on on which routers?

I would hate to change IPs at a few of these offices as one of them are large, and carry alot of statics.

Here is a rough design. Sorry for the crude design, I do not have Visio installed on this PC.



Re: Will this work?

It depends on what MPLS services you bought. Assuming you bought layer 3 MPLS (the most popular) you keep your existing address space and peer with the ISP routers to move IP traffic between your sites.

New Member

Re: Will this work?

Sorry, should have clarified that. We do not manage the MPLS equipment and our carrier just gives us an ethernet handoff that is essentially a bridged connection from our main office.

This is the reason we need to put Routers in place, to limit the switched traffic. Does that explanation suffice? Thanks for any suggestions!

Re: Will this work?

It's Bridged? Do you have a reason for it? Now I'm confused!

New Member

Re: Will this work?

I guess? The carrier just gives us an ethernet drop off of their Zhone (equipment name) box that essentially combines our existing TI's into 1 ethernet drop. Then that box taps into a few others and into their fibre loop.

We do not manage any of that equipment. Some of those offices only connect 1.5mb and some 3-5mbs. So, to limit broadcast, unecessary traffic, etc. we decided to place routers at each site to assign different IPs.

Sorry if I'm still not making sense :(

Re: Will this work?

What you want to do makes sense, but I would x2 check with the ISP and makes sure that these will be bridged connections, not layer3 links. Is that possible?

Hall of Fame Super Silver

Re: Will this work?

Hello Kean,

you just need to place at least one router at each site including the headquarters.

The ip proxy-arp has to be enabled on the LAN interfaces (towards the customer vlans of each site) internal to each site.

The ip proxy-arp if you have Pcs in the customer vlans that think to be on broader subnets or the 10/8 major network.

To complete the solution you also need to use a dynamic routing protocol so that the routers can know which is the right next-hop (172.1.1.x) for each address.

I would not recommend the usage of static routes in your case to be able to detect if one site is not available.

Check with your provider if you can run a routing protocol over the "WAN ethernet" it should be possible.

The ARP broadcast sent by an end user PC will never go over the "WAN ethernet" just for the broadcast firewall capability of the routers.

To improve the solution you could use the modular QoS to take in account the BW limitations of each site using a shaper outgoing each "WAN ethernet" less then the CIR limit.

Hope to help


New Member

Re: Will this work?

Thanks guys for both of your recommendations. I know that this is a bridged scenario because we already had a smaller site without a router that was already running. We have sat on multiple conference calls with our carrier and verified.

We have been using RIPv2, and the site in question we got working on Friday.

I would think since remote office 10.2.3.x is on the same network as corporate 10.1.3.x but physically seperated by routed network 172.1.1.x, a default permanent route (ip route permanent) would have to be placed at each remote site to connect back to the 172 network of corporate. Is this right?

We are also using ip pim dense-mode on each of our interfaces, so the ethernet based phones can conference to corporate, and the lights and announcement features would work (all use multicast). When we had just 1 router in between this worked fine, now it's not working. Any special needs that need to take place?

Thanks again!