When using Internet Sharing in 10.2, a DHCP Server service is created with an IP address, and then a subsequent range is set aside for clients. From my personal experience, it appears that OS X takes the IP address of the shared interface for the DHCP Server address, and the rest of the range for the clients. This is all well and good, except that if you change the IP address of the shared interface, it does not change the DHCP Server address, nor the client address range. In other words, if I originally had 10.0.0.1 as the IP address for the shared interface, and subsequently changed it to 192.168.0.1, then the interface now has 2 IP addresses. The DHCP Server service will use 10.0.0.1 and its clients will use 10.0.0.2-10.0.0.255 (depending on the mask). (A bizarre variation to this rule seems to be my G4, on which I am sharing the Airport network. No matter what I change the IP address to in the control panel, IFCONFIG will not show it and I cannot ping it locally. It will only show the original address--the one that DHCP is using.)
This is a problem for me, because the first time I set it up, I was just kind of playing around and hadn't thought out what address I really wanted to use. Because of VPN'ing to my workplace, I need to modify the address to not conflict with addresses at my workplace (both are in private IP space). I understand networking, but am no UNIX guru (I administer a Windows network at my job), and I have been unable to figure out where to adjust this. Common sense tells me that there must be some config file somewhere with this information, but I've had no luck finding it.
Can anyone out there tell me how I can tweak the DHCP settings for Internet Sharing?
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