# Can't bridge wlan0

## binro

I used to using a bridge to enable networking for kvm machines by bridging eth0 and tap0. Now I want to do it on my laptop but I get:

topaz robin # brctl addbr br0

topaz robin # brctl addif br0 wlan0

can't add wlan0 to bridge br0: Operation not supported

Searching gets a lot of hits but the solution is not obvious. Using hostapd is suggested but it seems to be incompatible with wicd network manager, which I use. I am using the 2.6.39-r2 kernel and something I read said bridging wlan is just not possible any more. Any thoughts on this?

TIA

----------

## BradN

Bridging wlan cards was always a PITA because if I recall correctly, there was no proper way to get most cards/drivers to send alternate MAC source addresses.  I had tried it once also and couldn't get it to work.

That said, some of the better drivers may have ways of doing this, or else maybe it is possible to use routing instead of bridging.

According to http://www.gentoo-wiki.info/Bridging ...

 *Quote:*   

> The driver could work around this restriction by creating its own MAC headers (802.11 headers instead of 802.3, and putting the right bits in the right place), but in fact most vendors don't provide the specification on how to this with their hardware (when they don't explicitly prevent it in hardware, to force you to buy their Access Points). 

 

Otherwise, I wonder if it's possible to implement a sort of MAC address based routing system where ARP packets are translated and all devices trying to talk to something on the other end of the link just resolve those IP's to the wireless card's MAC and the machine hosting the wireless card must translate MAC addresses based on the IPs referenced... I suspect there may be more work to it than that, perhaps involving DHCP translation, and maybe other low level protocols.

Basically, it'd no longer be a low level ethernet bridge, but rather something that acts close enough to one for IP packets.  Multipath links between the two segments may be more difficult or impossible then, but I don't know much about that to say for sure.

----------

