troubleshooting Question

Three Branch Office Connectivity

Avatar of kevkline
kevkline asked on
Routers
4 Comments2 Solutions435 ViewsLast Modified:
I currently have three branch offices connected in a triangle with the following scenario:

Each of the three are connected via serial to point-to-point single T-1's.  Each link currently has it's own network.  Two serial cards in each router.  One going to each directly connected site.  Pretty standard I guess.  Three inside networks (10.1.1.0, 10.1.2.0 and 10.1.3.0).

Router A---------10.1.12.0----------Router B
Router A---------10.1.23.0----------Router C

Router B---------10.1.12.0----------Router A
Router B---------10.1.13.0----------Router C

Router C---------10.1.23.0---------Router A
Router C---------10.1.13.0---------Router B

I am going to be getting rid of the T-1's and converting to a 10 Mbps fiber based MPLS (AT&T calls this OPT-E-MAN) which is actually a switched network and not a routed network although I can route it of course.

I am not going to be getting rid of the routers I currently have (Cisco 2811, 2821 and 2851) because they are already doing other things and I would like to keep a segmented routed network.  Router A has two PRI's for voice and an FXO card for paging, Routers B and C each have 1 PRI for voice and one FXO for paging.

Each router has 1 extra available ethernet port.  I could configure the ports on Routers A and B to be on the same network (say 10.1.4.1 and 10.1.4.2) and they should talk fine.  But without another ethernet port, what is the best way to connect Router C so it can talk to Router A and B?

Can I put three routers with IPs on the same network, say 10.1.4.0, plugged into the same switched network and be able to get to the correct network on the other side of the router?  I am thinking this should work.

Proposed:

Router A------ 10.1.4.1----------- (with the 10.1.1.0 network behind it)
Router B-------10.1.4.2-----------(with the 10.1.2.0 network behind it)
Router C-------10.1.4.3-----------(with the 10.1.3.0 network behind it)

Will this route OK?

Or is it possible to subinterface an ethernet port so that one port would reside on two networks?

Maybe I am overthinking this, but any thoughts would be greatly appreciated!
ASKER CERTIFIED SOLUTION
ck459

Our community of experts have been thoroughly vetted for their expertise and industry experience.

Join our community to see this answer!
Unlock 2 Answers and 4 Comments.
Start Free Trial
Learn from the best

Network and collaborate with thousands of CTOs, CISOs, and IT Pros rooting for you and your success.

Andrew Hancock - VMware vExpert
See if this solution works for you by signing up for a 7 day free trial.
Unlock 2 Answers and 4 Comments.
Try for 7 days

”The time we save is the biggest benefit of E-E to our team. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange.

-Mike Kapnisakis, Warner Bros