Bridging a wired network with an ad-hoc wireless

Kilroy01 · #1 (**permalink**) 08-03-2006, 11:13 AM

I previously posted this in the Network Troubleshooting section, but decided to move here due to lack of responses. Mod's please delete other post.

I have a Dell Dimension 8200 running WinMCE2002 sp2. I recently bought
a laptop and setup a wireless network using a USR5421 Wireless MAXg USB Adapter on the Dell. I have had no trouble with this setup until I
plug the Dell into a wired network with my other PC's. As soon as I
connect the cable, the wireless link to the laptop drops and will not
reconnect until I unplug the cable. It still sees the wireless signal, but that is all. I have tried this with the Dell in both bridged and non-bridged configurations. I know that MCE is cripped by Microsoft so that it will not log into domains, but I'm only using a workgroup on both networks so this shouldn't apply. The Dell works fine with either network, just not at the same time. I know that I could buy a wireless router and get around the problem, but we only have dial-up in this area and I can't justify the expense when this configuration should work. I'm at my wit's end with this. Anyone have any ideas?

NZLamb · #2 (**permalink**) 08-06-2006, 11:16 AM

Are both networks on the Dell on the same IP range? This will give the problems you describe.

Kilroy01 · #3 (**permalink**) 08-07-2006, 06:02 PM

Yes. Both networks are using 192.168.0.xxx.

NZLamb · #4 (**permalink**) 08-08-2006, 06:26 AM

Ah that explains it. Windows (and many other operating systems) will not work correctly when assigning multiple IPs in the same subnet to different interfaces.

Basically what it boils down to is the computer isn't sure which interface to send outgoing data from as they both claim to be able to reach the same destination network. All of the outgoing data ends up being sent out of the interface with the lowest metric (by default the fastest interface) or if the metric values are the same, the adapter highest in the binding order. This often happens regardless of the interface it was received on.

Unfortunately the solution to this is basically either to join the two networks together or set up one to use a different IP range from the other.

Kilroy01 · #5 (**permalink**) 08-08-2006, 01:42 PM

Joining the two networks together is precisely what I was trying to do. I wanted a wireless laptop connected to the Dell to be able to see the other computers connected to the Dell by wired network and vice versa. I'm unable to do testing at the moment, but if I use a different IP range for the two interfaces, then both should work? But will the two networks be able to see each other? Or will bridging the connections allow that?

NZLamb · #6 (**permalink**) 08-09-2006, 06:54 AM

Oh I see now. Bridging the connections usually should mean both networks can talk using the same IP range but in your situation there is a catch. The 802.11 specifications unfortunately do not allow for bridging of a wireless client device to other devices, hence why you probably found it didn't work on your laptop.

To work around this, try setting one network to use a different IP range and enable IP routing on the laptop. To do this in Windows 2000 or XP, browse to the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\Tcpip\Parameters. Look for the IPEnableRouter entry and change its value to 1. You will proabably need to reboot for this to take effect.

Lastly, once you have this set up all the machines on each network will need a static route configured to reach the other network via that laptop. If you already have a router configured on each side then you can add it to that instead. If you don't have a router already, set each machine to use the laptop as its default gateway.