On Mon, 08 Aug 2005 23:46:37 GMT, "paranoid"
<seanNO@SPAMunhookedmusic.com> wrote:

>We are responsible for fixing a wirless hotel problem. Uses about 15 access
>points.
>
>Problem is, the network guy here says, that dhcp just stops working. It
>seems that the wireless access points are hard-wired into a switch into a
>router serving dhcp. The netowrk guy claims that everytime dhcp stops
>working, he can walk the hotel with his laprop, and find someone serving a
>wirless signal. He says he has seen cell phones going into some type of
>wireless router serving up wireless for the user.

My guess(tm) is that you have more than one DHCP server running on the
network. I don't know where it's hiding, or in what box, but it's
there. The usual culprit is a Windoze 2003 server which enabled the
DHCP server by default. It also has some nifty security features
which prevents DHCP from working.

Another typical screwup is to have the DHCP server IP address
duplicated by a client computah with a static IP address. This
happens often when clueless users discover that DHCP had failed, and
decide to assign their own static IP addresses to their own computah.
They frequently punch in the IP address of the router/gateway/DCHP
server as their own IP address and cause everything to get muddled.

>This then knocks off the whole hotel wireless network. If he asks the
>customer to turn it off, it works. He claims this is the case everytime it
>goes down...

How is this customers client configured? DHCP assigned IP's or are
they playing static IP as a backup for the failed DHCP server?

>My theory is that the wireless access points at some point must go into
>repeater mode. We almost cannot get into these things ( ZYair b-420) ,
>because they are in bridge mode, therefore dont have an ip address.

Muddle. *ALL* (and I do mean *ALL*) wireless is bridging. Everything
is handled at the MAC address level (layer 2). There are no IP
addresses involved in bridging. The only thing the IP address of the
router does is allow you access to the access point for configuration.
You don't need this IP address for anything else, it will work the
same with literally any unused IP address, and will not affect
wireless bridging in any way. (It's not the IP address of the
wireless access points).

>The only way that someone serving dhcp would screw with the whole hotel
>network would be if these things are in repeater mode?

I don't think so. In the repeater mode, the ethernet port goes
comatose to the network. It wouldn't work at all in the repeater mode
unless configured for a mesh. The B-420 doesn't do mesh, but I thing
the B-1000 does. I'm too lazy to look it up as I doubt it's a
wireless configuration issue.

>We are confused, and are currently trying to access the internal page of
>these access points....

What do you mean trying? They should have static IP's assigned that
are accessible from your LAN. Hopefully, these IP's are not in the
middle of the DHCP assigned address range or you will have yet another
mess to deal with.

>Any ideas?

Sure. Download a DHCP query tool from:
| http://www.weirdsolutions.com/weirdS...ytool_free.exe
Find out which server(s) are delivering DHCP IP addresses. You should
have only one. I'll guess(tm) that you have more than one including
one that's delivering a default route that points to a dead end (not
the internet). I doubt it's a cell phone doing it.

In addition, I'll guess(tm) that your IP address plan for these 15
access points and your network is a big mess.

Any chance you're simply running out of available IP addresses for
DHCP to assign? What box or server is playing DHCP server and how
many IP's do you have available for assignment? If the DHCP lease
time is rediculously long, the old leases will not expire in time to
deal with new arrivals. This is fatal in a convention environment
where literally hundreds of laptops and PDA's compete for perhaps 253
IP addresses.

You should also pay attention to roaming effects. Setup the system
so that the ARP table (MAC address to IP mapping in the router)
expires quickly. Run this test:
1. Connect to an access point and convince yourself that it works.
2. Now, move the laptop to another access point with the same
SSID and channel.
Do they track? Do you maintain the connection? Or does it go
comatose as in your description? If so, your router is holding onto
stale ARP table or router table entries from the initial connection
and screwing up roaming.
--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558