I spent a solid hour on the phone with Apple support, and they just don't get DHCP at all. You will eventually get the "we don't provide support for anything that you can't access and configure through the GUI. You're on your own, mate." if you keep probing them. Of course, I had one "genius" tech try to tell me that the VCI was set by the MAC address and that it couldn't be changed. I then proceeded to tell him what an ignorant ass he was.. explained what the OUI of the MAC is and why it exists, how it relates to dhcp client-identifier and how it has NOTHING to do with the dhcp vendor-class-identifier. In the end, he apologized for being a cocky ass and trying to just push me off the phone and thanked me for giving him an education.. but still no resolution.
It appears that, like M$ Windoze, the VCI on a Mac is locked up in a binary somewhere and you simply can't change it.
My workaround for this problem was:
- Download and install the XCODE compiler from the Mac Developer site.
- Download, compile and install the latest ISC DHCP package.
- Tweak the dhclient.conf file to include the following
send vendor-class-identifier "MSFT 5.0";
- ..and enjoy.
The whole operation took 35 minutes, most of which was spent watching the packages download. My machine works a treat now. No more issues with DHCP working for XP boxes and not my MBP. Don't be afraid of the ISC client. It works just fine, and doesn't conflict with the built-in client.