Macbook Pro DHCP issue

Question

We have one Macbook Pro user here who is on our Windows AD network (using his own machine unfortunately) but experiencing problems.
We have reserved an IP address to facilitate internet access\firewall rules, however whenever the user initiates any process involving substantial data transfer through the Ethernet port, the DHCP settings are stripped out & replaced by a local loopback address starting 169. & the network connection can only be restored by a reboot. Processes which have tripped this up include sending an email with a 10mb attachment, downloading a software update for firefox & even sending a network print request. This is a new error condition & it is perfectly possible that the user has installed an update on the macbook although he doesn’t seem to know whether in fact this is the case. The user is rather resistant to having his macbook reconfigured & I’m doubtful whether at this stage installing Parallels may be an option.
Could you suggest any troubleshooting approaches here?

Answer 1

if the users CPU is using a 169 IP address, then the CPU isn't talking to the DHCP server, so is self assigning an IP
Try redoing the DHCP server to not pass out the last available address for that particular subnet.
Then reconfigure the Mac as fixed IP for the address the DHCP server will not hand out.
That is, if you are using a full 255.0 subnet to support 254 computers on that subnet, stop dhcp addresses at 192.168.0.253, then configure the user for fixed IP 192.168.0.254, subnet 255.255.255.0, and gateway 192.168.0.1
use your wins and DNS server addresses in the appropriate locations on the Mac.
If you are using Exchange/entourage, you may need to configure those by fqdn or IP instead of netbios name.