Hi,
configure bootprelay add [vr ]
enable bootprelay ipv4 vlan
So you configure the DHCP server ip addresses on a virtual router (or VR-Default) and then enable it on the specific VLANs that are connected to that VR that need DHCP.
As far as I know, you can configure more than one DHCP server (one "configure" line per server, i think), and you'll just get the IP address of the server that replies first. The new Windows 2008 DHCP servers can be configured smart enough that both know what addresses have been given out - no more "80-20 splitting" mess like in older windows versions 🙂
Frank