OSX 10.5.7 DHCP issues with Win Serv 2003 - Requests previous network's IP, then fail

[funkypenguin]

Hi folks,

I travel a lot with my MacBook Pro, between home, and various clients. Most times, I connect to the client's network wirelessly. Over the past 2 months or so, at one particular client, I've been unable to obtain an IP address on the network. Normally I just use an ethernet cable, but today I decided to tackle the problem properly.

I looked at the DHCP logs on the Windows 2003 server, which supplies addresses for their network (192.168.2.x). To my surprise, I saw my requests from my MAC address requesting the IP 192.168.29.137, which is on my HOME subnet. (The last network I was on)

The DHCP server responded with a NACK, denying the lease. (obviously, it's the wrong subnet).

I've since tested with a 3rd wireless network, and sure enough, every time I get to this particular network, my Mac requests the IP address it previously held on the last wireless network it was on.

I note that I don't have this issue at a 3rd client, who also runs a Windows 2003 DHCP server.

I've tried increasing the DHCP timeout on my mac, by changing /System/Library/SystemConfiguration/IPConfiguration.bundle/Contents/Resources/IPConfiguration.xml and rebooting, but that had no effect, so I changed back

Does anybody have any experience / ideas?

Thanks!
David

 

[RandomKamikaze]

Well, that is a bit weird.

What's even more strange is that your Mac is telling the DHCP server what address it wants, as that isn't how it works.

What happens if you go to Network Preferences and ask it to renew the IP address?

What happens if you set yourself a reservation on the DHCP server where you are having problems?

 

[funkypenguin]

Well, that is a bit weird.

What's even more strange is that your Mac is telling the DHCP server what address it wants, as that isn't how it works.

What happens if you go to Network Preferences and ask it to renew the IP address?

Nothing.. the behaviour is the same as if I'd turned the airport on and off again. Strangely, sometimes I don't see ANY logs on the DHCP server, failure or otherwise.

What happens if you set yourself a reservation on the DHCP server where you are having problems?

It doesn't seem to make a difference, it still doesn't get past the NACK stage

If, as you say, this behaviour is not the norm, I might try doing a tcpdump / wireshark capture to see what's _really_ going on ...

 

[RandomKamikaze]

A quick search of Google suggests that the DHCP server may be out of addresses or that it might be trying to assign you an address which has been statically set elsewhere but set as a reservation.

There might also be a rogue server, but this is unlikely as others would have noticed.

If you do a Wireshark trace it would be interesting. Obivously you know of the way DHCP works and the packets you should expect to see?

I'm assuming they haven't got MAC address filtering setup or anything nasty like that?

This quick search on Wikipedia might provide some insight:

A client can also request its last-known IP address (in the example below, 192.168.1.100). If the client is still in a network where this IP is valid, the server might grant the request. Otherwise, it depends whether the server is set up as authoritative or not. An authoritative server will deny the request, making the client ask for a new IP immediately. A non-authoritative server simply ignores the request, leading to an implementation-dependent timeout for the client to give up on the request and ask for a new IP address.

Sounds like your Mac isn't completing the process and dropping your last known IP

 

[funkypenguin]

If you do a Wireshark trace it would be interesting. Obivously you know of the way DHCP works and the packets you should expect to see?

Interestingly, I only see my OUTBOUND DHCP requests in my wireshark capture. Not inbound. Hmm..

I'm assuming they haven't got MAC address filtering setup or anything nasty like that?

Not to the best of my knowledge, and what's interesting is that DHCP works fine on the ethernet port, against the same server. Just not wireless

This quick search on Wikipedia might provide some insight:

A client can also request its last-known IP address (in the example below, 192.168.1.100). If the client is still in a network where this IP is valid, the server might grant the request. Otherwise, it depends whether the server is set up as authoritative or not. An authoritative server will deny the request, making the client ask for a new IP immediately. A non-authoritative server simply ignores the request, leading to an implementation-dependent timeout for the client to give up on the request and ask for a new IP address.

Sounds like your Mac isn't completing the process and dropping your last known IP

Now that's interesting.. I looked at the 2003 DHCP server, and it seems to be "Authorized". (I.e., I see an option to un-authorize it). However, this server servers multiple subnets, and I don't see how to check authority for a particular subnet/scope..

 

[RandomKamikaze]

I would have a look at that Wireless network. Sounds like there is a layer of authorization there that is denying your computer access