Bridging and Ad Hoc Wireless Network Into an Existing Wired Network
Posted on 2004-07-31
Let’s see if I can explain this as best I can. I have an existing home network with a handful of nodes all connecting via plain ole Ethernet to a home NAT router out through my broadband connection. Everything works pretty good. One thing that I am able to do that is important in my final solution is that I am able to forward ports from the NAT router to any node inside my network.
Now everything worked great until I stumbled upon two rather inexpensive WiFi adapters, and I thought wouldn't it be great for a little cash to be able to use the laptop wirelessly? So I got my hands on a PCI WiFi card and stuck it into an XP Pro desktop computer and a PCMCIA WiFi card and put it into the XP Pro laptop. I was able to give them there own addresses separate from the existing network. The two computers could ping each other and browse each others files and all sorts of goodness, except that the laptop couldn't use any other resources nor could any other node access the laptop. (Point is I know the wireless link works fine.)
So I started looking around and found out about the Bridging feature in Windows XP. There a probably a million websites (that are probably copies of some master article somewhere since they all have the same screenshots) that say oh yeah bridging is great, once you have the two network segments setup you just right click and pick bridge connections and everything will just work. So I give it a try, I tell the XP Pro Desktop to bridge the connections and if grinds away for a minute and looks like everything depicted on the million websites that was supposed to happen happened. So I go to the laptop, and as far as I can tell only change is the wireless connection is broken. They still have link, but they won't talk. I start looking around, and the bridge computer shows that it only has one IP address from the original network. This makes sense to me that it should only have one address since the bridge is supposed to make two networks into one. So I go into the laptop and tell the WiFi connection to use DHCP. DHCP fails and I say to myself no problem, I'll just do it by hand. So I change the laptops WiFi adapter to use an address that fits the existing network scheme (including gateway, and DNS server). Of course that doesn't fix it either. I know that for most networking changes in XP you don't need a restart but on the off chance that bridging is different I go into a restart frenzy, which doesn't help at all.
So I start searching around. The only thing that I find is that some NICs have compatibility mode issues in the bridge. So I run the netsh bridge show adapters command, and sure enough both adapters have force compatibility disabled like the MS website I found said. So I run the netsh commands to force them to enable compatibility (which I imagine is some software work around for NICs that don't support promiscuous mode.) All this really does is break things worse. The Bridge computer no can't talk to either the plain Ethernet network or the WiFi network. So I put things back with the netsh command to undo the damage.
The only work around I have found is to use Internet Connection Sharing on the Desktop. This does let me use the internet from the laptop via the WiFi and lets me use all the resources on the plain Ethernet network, but nothing can access the laptop except the Desktop running the connection sharing, which isn't the solution I want.
I suppose what I would like is help getting the bridge to work as advertised so that the laptop will have a normal address on the network, and I will be able to forward ports from the outside internet to it. So what did I miss?