Okay, it's been awhile since I set up our dhcp at work, but if I remember correctly, dhcp requests don't usually route.
You are entirely correct, they do not.
I believe that we had to set up our central router (a Cisco Catalyst 3550 set up to route instead of switch) to forward the dhcp requests to the dhcp server on our server subnet. Otherwise we'd have had to have had a dhcp server on each subnet.
You have three options: (a) a separate DHCP server on each subnet; (b) setting up each subnet's router to forward those packets as you did; or (c) using the dhcrelay program included in ISC's dhcpd on each subnet.
Cheers,
-- Rodolfo J. Paiz rpaiz@xxxxxxxxxxxxxx http://www.simpaticus.com
