http://hints.macworld.com/article.php?story=20060124152826491
Shows how to find the address of the DHCP server that issued your current lease on a Mac.
Similar to ‘show ip dhcp lease’ on Cisco, ‘ipconfig /all’ on Windows, or one of… well, I guess I’m not sure how to tell with dhcpcd OR dhclient under Linux. Something else to figure out at some point.