Windows – Two NIC cards with the same metric – Internet traffic going out the wrong one

The command you're looking for is route add:

route | Microsoft Docs

For your setup, I think the syntax is:

route add 10.183.0.0 mask 255.255.0.0 10.183.148.5

This will send all the traffic for 10.183.x.x to the next hop address of 10.183.148.5 which your system already knows is off of your ethernet nic, and any traffic that doesn't match a route, will be grabbed by your default route and head through your 3g connection. It also looks like your network assigns multiple routers, so you might want to double it up and add the routes for 10.183.148.6 and .7 as well.

You might need to be careful if your network has stuff not in the 10.183 range, you may need to add more routes. You may also be able to get away with routing all of 10.0.0.0/8 to your corporate network, since windows will have a more specific route, but i'm not 100% sure on that since your 3g card is giving you an IP in the 10.x.x.x range.

unless you set up a DHCP server on network B this config is going to cause you a world of pain.

An alternative is to put a second nic in your DHCP server and connect it to network B. Then you can have two DHCP zones, serving out two different address ranges.

J