Bridging and Ad Hoc Wireless Network Into an Existing Wired Network

Posted on 2004-07-31
Last Modified: 2013-12-07
Hello Everybody.

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?
Question by:vtechpilot
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Accepted Solution

pseudocyber earned 250 total points
ID: 11685223
Ok, if I understand this right, you've got a broadband router/switch with a couple nodes and everything is great.  Then, you've got two laptops and they were on the wire but you put wireless in them and that works fine except they're not on the wired network anymore.

so, on the wireless network you created a seperate network and the two could communicate wirelessly no problem.  Then, you're connecting one of them wired and wireless and you want the other wireless to flow through the first to the wired network.

At this point, what I think you should do is uninstall the wireless connections and get everything working wired again.  Then, install the wireless nic on your "bridge" laptop and before you configure anything else for it, select the two adapters and bridge them.  This will have the effect of putting your wireless on the same layer 2 network (ethernet).  This bridge laptop should have only 1 IP address from your router.

Then on the other laptop, put in the wireless and get it to connect to the bridge laptop via ad hoc mode.  TCP/IP should be configured to dynamically receive an IP address from the network.  The way it SHOULD work is that the nic will talked to the other bridged nic who will send traffic onto the wired network to the router and the reverse.

In my opinion, the ideal situation would be to pick up a wireless router/switch off Ebay or your local electronics store and have both wireless laptops communicate with the Wireless Access Point (WAP) directly.  You might be able to pick one up for as little as $50.

Hope this helps.

Assisted Solution

miloudi earned 250 total points
ID: 11685369


It would do it to get a wireless access point, but the thing should work even with the lousy MS bridging software.
The way you are doing it seems right, you can try what pseudosyder suggested, however i still think that it is your cards....
Getting a wireless AP would be cheaper than two good WNICS, after all.

Author Comment

ID: 11685378
Well you almost have the Idea, One laptop, the second wireless node is a desktop. Just because I hate it when I suggest something and they don't try it. I went through your recommendation. but I still get the same results. On the bridge machine everything looks OK, and on the laptop, it gets link, but can't talk to the bridge machine at all (DHCP or manual). The problem as I see it is that the a bridge is just supposed to work, and it doesn't. I do agree an ideal would be to just get an Access Point, but money is a little two tight for that, the only reason I am trying this is I got a ridiculous deal on the nics in the first place. Besided solving the puzzle is fun too.
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Author Comment

ID: 11685393
Miloudi, yes an access point maybe cheaper than two good nics, but an access point and a cheap nic is still more than two cheap nics. Being cheap got me this trouble in the first place. But you see the problem; "the thing should work even with the lousy MS bridging software."

That is exactly what I am trying to solve. It should work but doesn't. Why?

Expert Comment

ID: 11685615

What kind cards are you using anyways? do you have the latest drivers.?
R u able to buy two good linksys cards and return them...?
how about the the wired AP? does it have the latest firmware?


Author Comment

ID: 11685706
Both are DLink Products DWL-G510 in the desktop and DWL-G630 in the laptop. The shipping drivers are the latest thats available from the manufacturer. Yes they have the latest drivers. No I am not going to run out an buy something. The Wired NAT router does have the latest firmware. I appreciate the suggestions, but all stuff thats been done. However I did start looking around in the would be bridge machine, and when I told the device manager to show hidden stuff, it showed about 90 ok, more like 12, nics in there. some of which haven't been in the machine for quite some time. I am going to start persuing the notion that the network device registry in this machine is borked from all my abuse. Its been a while since that machine had a fresh install anyway. I'm still taking sugestions though.

Author Comment

ID: 11686325
I have noticed some odd behavior since putting a fresh copy of windows on the bridge machine. Both wireless nodes send traffic, but nether of them show any recieption of traffic. It is as though once the connection is established they can no longer properly address eachother. Like each is sending the the wrong MAC address.

Author Comment

ID: 11690997
Well I have come to the conclusion that this really can't be done with the equipment I have. Not every networking device has the hardware capability to run the Windows XP bridge. Both PseudoCyber and Miloudi are right, an Access Point would be a better solution.

Expert Comment

ID: 11839498
Have you triedAre you trying to divide the network in subnets, different IP ranges? If so you could try to
put the GW of the laptop pointed to the Desktop and using route add command on the Desktop.
just an idea.

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