# DHCP won't work over wireless?

## BradN

I've got a D-Link DWL-650 pcmcia card in my notebook that I'm pretty sure is configured properly, and it's talking to a D-Link DWL-900AP access point apparently just fine.  The access point is connected to a 5 port hub that runs most of my network here.

Everything works fine if I set up stuff with static IP's in the 10.*.*.* range, but I'm trying to just let the motorola surfboard cable modem assign IP addresses to everything with DHCP.  This works OK with multiple computers to begin with, so that shouldn't be an issue.  But, over wireless, the DHCP doesn't seem to work to configure my notebook.

Any suggestions?  I guess I might have to set up my wireless behind another linux box running NAT for it otherwise.  Perhaps the surfboard has been programmed to reject MAC addresses associated with wireless access points?

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## mikki

The problem is that your wireless devices need a different default gateway (the nap) than the other machines connected to the surfboard.

Does the d-link have a dhcp server? If so, you might be able to set up two network segments, one for the wired net, one for the wireless. The nap acts as a router.

For example, set the lan address of the surfboard to 10.0.0.1 and the internet (or wired) address of the nap to 10.0.0.2. Set the wireless address to 10.0.1.1 (assuming 24-bit mask: 255.255.255.0). Have both devices serve dhcp.

One thing you will have to do is give a static route to the surfboard telling it that all the 10.0.1.* addresses route through the nap.

Otherwise, you could just hardcode the laptop default gateway to the nap address. 

Hope this helps!

Mikki

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## BradN

The problem is that the D-Link is supposed to route DHCP requests - it can't act as a DHCP server (although, it is supposed to be able to act as a DHCP client to get it's own IP address, which doesn't seem to work either), and it doesn't do NAT by itself.  It should just be acting as a strict bridge (and with static IP's, it seems to be doing that just fine).  Also, the surfboard is something I'm not able to configure (it's the cable company's).

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## mikki

I see. Sounds like the nap isn't bridging at the physical layer, so the dhcp server is only seeing requests with the nap mac address, not the laptop's.

Have a packet sniffer handy? See what happens when various clients try to allocate addresses. My guess is that they all look the same.

Mikki

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## BradN

That could be the case.  If that's it, what can I do to make it work?  Also, I've tried setting up the wireless with the same settings (IP/gateway/DNS) as the DHCP configured ethernet had, and it still can't get any response out of the cable modem at least.  I can't ping the gateway (which I assume is behind the cable modem, and not the actual cable modem itself) either.

With the configuration hacked up like that, I can however ping my desktop which was DHCP configured also (they're on the same subnet, so that's to be expected I guess).

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## mikki

You said the static configuration worked? Sounds like your best bet.  You *could* set up a dhcp server, but it would have to be on the wireless side.

Mikki

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## BradN

I just went and bought a different access point (this one's actually a "broadband router", so it should be able to work somehow).

When I say the static configuration worked, it only worked to my local computers - not to the internet through the cable modem, which is what I really want out of it.  I could run one computer with NAT to deal with it, but I'd like to avoid that if possible.

I'll see if I can make this access point work any better.

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## mikki

Good idea! These things are so cheap right now, especially 802.11b stuff!

What did you get?

Mikki

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## BradN

The one I got now was just a higher up model D-Link (wireless + 1 uplink port + 4 ports for the internal network)

The problem turned out to be my cable modem rejecting any new MAC addresses (there must be a limit coded into it to allow only x amount of network cards connected to it).  I was able to reset the cable modem and allow new mac addresses.  I think I'll keep the new base station anyway because it was only like 10$ more and has lots of fun NAT stuff if I need to attach more stuff without worrying about the cable modem.

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