[Dnsmasq-discuss] DHCP over a wireless bridge

John Kaye john at sparkisys.com
Thu Jan 9 17:50:12 GMT 2014

Thanks Daniel. The information you provided is very helpful indeed. I've 
integrated relayd and I'm testing it now.


On 1/7/14 7:28 PM, Daniel Dickinson wrote:
> Your basic problem is this:
> http://wiki.openwrt.org/doc/howto/clientmode?s[]=client&s[]=bridge#problem.using.standard.client.mode
> You are doing a wireless bridge.  Something like relayd may allow you to
> work around the issue (mentioned later on the same page), but the basic
> problem is that IEEE802.11 isn't designed to allow for wireless bridges
> (missing source mac addresses on the client wireless).
> The other way (like a wired LAN to wireless AP) works, but wireless
> connection to share a wired connection is problematic
> Regards,
> Daniel
> On 07/01/14 09:11 PM, John Kaye wrote:
>> Hi All,
>> I'm developing a transparent wireless bridge for a client who
>> manufactures printers. The printers connect through the Ethernet side
>> of the bridge and the wireless side of the bridge associates with an AP.
>> The AP will reject frames from the printers because their source
>> address is different from the source address that is associated with
>> the AP; to resolve that, ebtables is used to snat the source address
>> of the frames from the printers, and everything flows.
>> Everything flows nicely when the printers are configured with static
>> IPs. When the printers are configured to use DHCP, the AP never
>> delivers an IP, even though it receives a discovery request from the
>> printers. I assume the AP doesn't respond because the DCHP DISCOVER
>> frame has the client mac address encoded within it, which doesn't
>> match the address that it is associated with, so it's ignored. Does
>> that sound correct?
>> To enable the printers to get IP addresses from the AP, it would seem
>> that a DHCP relay proxy of some sort would need be to implemented to
>> run on the bridge. The proxy would relay DHCP requests to the AP and
>> return addresses to the printers. Does that sounds feasible?
>> If my assumptions are correct, can dnsmasq be configured as a DHCP
>> relay proxy? If so, are there examples of how it can be done?
>> If my assumptions are not correct (which I imagine they are),  are
>> there other options?
>> I truly appreciate any guidance. My networking knowledge is limited,
>> though it is growing by leaps and bounds!
>> Cheers,
>> -John
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