Problem Bridging NIC's in windows XP

January 29, 2010 at 19:24:37
Specs: Windows XP
I've seen this problem posted on a variety of sites and never seen a real solution. I'll try to explain everything, but please understand that I am familiar with ICS and I am aware that they make wireless bridge boxes you can buy but I'm not interested in those solutions.

I have a small home network with the following archetecture:

Cable modem
linksys wrt54g2 wireless router
| |-----------------|--------------|
CPU 1 Laptop 1 Laptop 2 CPU 2

I would like to create a small network addition attached to CPU 2 of all wired connections, I.E.:

Linksys 5 Port Hub
Variety of Media Hardware
(XBox, Blueray, etc.)

CPU 2 already possesses a working Wireless NIC (Netgear MA311) through which it connect to the router, and a currently unused but funcional 10/100 ethernet NIC.

I do not want to purchase a wireless bridge as I already have all the nessisary hardware and don't want to waste the money. I cannot use ICS as I already use the IP range by ICS for the existing router, and more importantly I need the network to be transparent. I have services running on CPU 1 that I want to access from the media hardware and ICS result in isolated network zones where this is not possible. Likewise the use of another router as a gateway results in isolated network zones.

Fortunatly Windows XP has a built in utility to address just this. Unfortunatly I can't get it to function as described in the liturature.

I have been attempting (in vain) to bridge the wired and wireless NIC's on CPU 2 you create a larger network on a single subnet. The windows bridge utility forms the bridge but the result is that the bridge gets a private IP (APIPA) instead of the IP previously belonging to the MA311. I immediatly lose the internet gateway and connectivity with everything. I've tried versions of ICS, setting IP's manually, configuring alternative IP only. Nothing works. I can't ping anything from CPU 2 (times out, not outright failure) or anything on the far side of CPU 2. The weird thing is, as soon as I remove the Wireless connection from the bridge I get connectivity with the internet and everything on the router side again. I tried one of the laptops on the far side of CPU 2 for testing but I can't get it to connect to anything through the bridge, but it shows up in Network neighborhood from CPU 2 (although I still can't ping it's IP), but not vis-versa.

I'm sure I've left some details out, but you get the picture. Where do I go from here?

See More: Problem Bridging NICs in windows XP

Report •

January 30, 2010 at 12:55:02
I've solved my problem. This solution may or may not work for you.

The problem aparently boiled down to my wireless NIC incorrectly reporting it's status to the computer. In particular the NIC was probably incorrectly reporting itself as supporting Promiscuity Mode (wiki this if you want more info). The solution is to force that adapter into "Compatability mode"

The comands to do this are, from the command prompt:

netsh bridge show a

(note the index number of your wireless card)

netsh bridge set a 1 e

(where 1 is the index of my wireless NIC)

netsh bridge show a

The status of the NIC should change to compatability enabled. Presto, all APIPA's all go away and the whole network now runs seemlessly. There is a lot of detail on exactly what this is and what it's doing. I would recommend reading this article for more information, it's what finally got me on the right track:

It took me over 10 hours to find this solution, and only 30 seconds to impliment it. I hope this saves other a lot of heartache and headache.

Report •
Related Solutions

Ask Question