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I asked this on another site recently, but I figured this might be a good place to ask this as well:

Please take a look at the diagram below. My question is in regards to computer "C" in the middle of the diagram. It has three NIC cards. It needs to be able to talk to computers A1, A2, A3, B1, B2, and B3. To do that, I will need to put static routes into computer C's route table. My question is what are the exact static route entries that I need to put into the route table to achieve this? In other words, what does "route print" look like after I have entered the static routes?

This would be on Windows 7 or Windows XP

Edit: I should say I've done quite a bit of research on this, but I'm still a little shaky on the exact entries to achieve this.
This link from Microsoft is helpful with examples - but it is not totally clicking for me

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What are the IP addresses of Router A and Router B? Are RouterA and router B the default GW for Networks behind them? – Doon May 18 '12 at 17:42
Sorry I should have put that in. Every router port would be the .1 address for the network that it is connected to. So on router A, the port that is facing switch A1 would be Therefore, computer A1 would have set as its default gateway. – jstevens13 May 18 '12 at 18:48
I assume those are just placeholder addresses, but just in case they aren't: you shouldn't be using 172.168.x.x on your internal network; that address space is on the public internet, owned by AOL. RFC1918 ranges (10/8, 172.16/12, 192.168/16) and addresses you own are the only addresses you should ever use. – Shane Madden May 18 '12 at 20:14
Shane - Those are placeholder addresses - but thank you for the heads-up! – jstevens13 May 18 '12 at 21:09
up vote 2 down vote accepted

A quick stab with the following assumptions:

Router A has IP address:, and has correct routes/or its default pointing to
Router B has IP address:, and has correct routes/or its default pointing to    

You need to route and to You need to route and to


  route -p add MASK
  route -p add MASK 
  route -p add MASK 
  route -p add MASK 

The -p will make them persistent across reboots.

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To reply to your first assumption: yes the port or router A that is facing computer C would have an IP address of and the port of router B that is facing computer C is The routers are already setup to route between all 4 of their ports respectively. – jstevens13 May 18 '12 at 18:52
I'm not sure I understand your second assumption though (and maybe this was just a type-o) but all subnets are /24 subnets. So to restate the second assumption. I need computer C on its interface to be able to talk to computers on,, networks as well as, on its interface to be able to talk to computers on,, networks. – jstevens13 May 18 '12 at 18:58
i was just making sure that the routers could already talk both ways. The /23 is a covering route, just a more efficient way of saying and but you could easily just route them all by /24 (Sorry I am mostly a Network wonk, so always try to aggregate routes wherever possible). – Doon May 19 '12 at 1:26
@jstevens13: Remember, it won't do much good for C to be able to reach a machine if those machines can't reach C too. So you'll need to add static routes on the default gateways of each network that needs tor each C. – David Schwartz May 19 '12 at 4:38
@Doon I understand completely now. Thanks for the explanation and the answer! – jstevens13 May 19 '12 at 12:27

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