[Ignitionnet]

Ya. They'll run through their cache and if no hit use the leasequery protocol to ask DHCP servers for information.

All CMTS know where the DHCP server(s) is/are anyway. They need to so that they can forward DHCP broadcasts to them.

Just FYI this isn't wasting bandwidth anywhere. The broadcasts shouldn't be consuming any of your downstream rate limit, and it's a broadcast at the cable level, not a broadcast message being unicast to each modem.