Network design question

We are planning to move few of our environments from the office server room to a datacenter, need to expand, but there is no more available physical space, cooling capacity issues, etc.
Number of office networks are currently all interconnected via SonicWall firewall acting as an internal router .
The plan is to use a metro layer 2 link from the office to the DC creating extension of the local 192.x network
The problem is that the Internet connection and few internal networks will stay in the office while other networks, including our development (10.x) network will have to be migrated to the DC.
Here comes the question: the only router that routes traffic is going to stay in the office, means there is no way for the office users to reach the 10.x subnet.
We can install additional router in DC and create static route on office router to forward all traffic coming to the DC networks to the DC router, but I am not sure if this workaround is going to work.
Another option is to get rid of the 10.x network and flatten the at least two of these networks (192 and 10) but considering the amount of work associated with this way it may take a few months of planning and executing this plan, something we do not have resources for.
My goal it to try and keep network design as simple as it possible.

What can work in our case?

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AkinsdNetwork AdministratorCommented:
You will need to create a different subnet for the devices you're migrating and then create route as you have mentioned.
You can't split 1 network accross 2 routers. Extending 192.x as you've mentioned won't be possible.
Check your options with your ISP for the options you have (Ethernet handoff or Private transport or MPLS etc)
Vasilax50Author Commented:
Just to make sure I've explained myself clearly.
If a user on 192 network needs to reach a server on 10 network, what are the possible options?
If a default gateway of user's PC is router 1, and on this router there is a static route forwarding traffic intended to 10 Network to router 2, would this setup work?

ThanksOffice to DC connectivity
If your default gateway is R1 ip address (according to addresses that I added to picture) on R1 for 192 network , and IP address of R2 that is attached to the same network is

You need to add static route on R1 router
ip route 10.x.x.x 255.x.x.x
in case that your 192 network is flat network.

In other words, your setup will work.

For networks other than 192 network, to be able to communicate with 10 network, on R2 you need either to set default route that points to R1 or static routes to other networks with next hop address points to R1.
I added IP addresses to simplify explanation
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AkinsdNetwork AdministratorCommented:
Yes, the setup will work as long as both routers know how to find each other.
Tory WCommented:
My suggestion would be to use your routers for layer 3 connectivity between each other then do layer 2 on the access switches. This would prevent you from having a broadcast domain stretching across two sites.

So for the example use:

 switch to 192.x.X.x network - - - - - - - - - -\                               L3                                  /- - - - - - - - 192.x.Y.x
switch to other Networks - - - - - - - - - - Router 1 - - - -  |   MetroE    |  - - - - Router 2 - - - - - -  10 Network
                           internet- - - - - - - - - - - - - -/

This way you can route across normal L3 network using VPN, MetroE or whatever you want/need. Then just route your networks back and forth using any routing protocol or even static routes.  This will allow you to grow to any size without major overhaul. It also separates your Layer2 traffic and would allow connectivity between all areas.  

Another way to do it would be to have a VPN set up between the sites so rather than have the internet hanging off of Router 1 you could use the Internet between the two sites. There are many factors that would have to fall into place for this to be best for your organization.  It really depends on how many users are on each area and what their requirements are.  This though may be one of the least expensive way to do it.

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Vasilax50Author Commented:
Decided to build a lab and test routing to make sure everything is going to work.

Used two routers, connected on 192 network (layer 2) to simulate MetroLink.

Both routers forward traffic to internal and external networks correctly, no need to flatten the networks.
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