Connect and use to multiple networks in Windows 7?

Question

The core of this questions I suppose is "How to I tell Windows 7 which interface to use for each network?"

My current set up is:

1) 10/100 cable connected to my corporate network, which is behind a tight firewall, but gives access to servers and stuff.

2) a USB 3G modem that once connected gives me access to all the internet goodness :)

It just happens that when I hit the connect on the 3G modem, Windows seems to try to use it for all the addresses and I loose access to LAN server (event though the cable is still connected).

I reckon there should be a way I could configure my Windows something of the sort "for networks 10.x.y.z use this interface, all the other use modem"

Can anyone tell me how do I do that?

[EDIT] Adding the route print as per request:

===========================================================================
Interface List
 53...00 Firefox 10 aa aa aa ......Juniper Network Connect Virtual Adapter
 71...........................Internet Everywhere Pro
 47...54 aa 9f aa aa aa ......Check Point Virtual Network Adapter For SSL Network Extender
 49...00 a0 c6 aa aa aa ......ZTE Wireless Ethernet Adapter
 28...00 22 fa aa aa aa ......Microsoft Virtual WiFi Miniport Adapter #3
 27...00 22 fa aa aa aa ......Intel(R) WiFi Link 5100 AGN #2
 22...00 24 7e aa aa aa ......Intel(R) 82567LM GBabit Network Connection
  1...........................Software Loopback Interface 1
 46...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter
 40...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #2
 43...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #3
 44...00 00 00 00 00 00 00 e0 Teredo Tunneling Pseudo-Interface
 21...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #5
 45...00 00 00 00 00 00 00 e0 Microsoft 6to4 Adapter
 51...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #4
 52...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #6
 54...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #7
===========================================================================

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0     10.113.148.1    10.113.148.71   4245
          0.0.0.0          0.0.0.0         On-link      90.172.28.92     31
     10.113.148.0    255.255.255.0         On-link     10.113.148.71   4501
    10.113.148.71  255.255.255.255         On-link     10.113.148.71   4501
   10.113.148.255  255.255.255.255         On-link     10.113.148.71   4501
     90.172.28.92  255.255.255.255         On-link      90.172.28.92    286
        127.0.0.0        255.0.0.0         On-link         127.0.0.1   4531
        127.0.0.1  255.255.255.255         On-link         127.0.0.1   4531
  127.255.255.255  255.255.255.255         On-link         127.0.0.1   4531
        224.0.0.0        240.0.0.0         On-link         127.0.0.1   4531
        224.0.0.0        240.0.0.0         On-link     10.113.148.71   4500
        224.0.0.0        240.0.0.0         On-link      90.172.28.92     31
  255.255.255.255  255.255.255.255         On-link         127.0.0.1   4531
  255.255.255.255  255.255.255.255         On-link     10.113.148.71   4501
  255.255.255.255  255.255.255.255         On-link      90.172.28.92    286
===========================================================================
Persistent Routes:
  None

Answer 1

if all of your company is on a 10.113.x.x network, add another route, for 10.113.0.0 255.255.0.0 to go to your local gateway, 10.113.148.71. (often there are other subnets that are involved.

Basically, that route table is saying if its on your local lan subnet, 10.113.148.x, use your lan card. the default routes are there for both, (the 0.0.0.0, which means "unknown"), but the 3g card has a MUCH lower priority.

That will work you just have to add all the routes you might need to access to the table to route out your lan card. (for example, maybe your mail server is on 10.113.149.1 or something). Basically, however big your companies subnet is.

Answer 2

Yep I can see the problem. You see the second line in the route table? that basically overrides all other connections, because it has such a small metric value.

On the local network connection in control panel, right-click -> properties -> select ipv4 click properties, click advanced. Somewhere there is a box to set the metric. Enter 1 in this box and see what happens. If this then bypasses your 3g dongle, we'll have to fix it by manually editing the routing table. I'll get you instructions as soon as I get near a windows PC (which may not be today, sorry)