Can ISC DHCP be configured to forward/route to another DHCP Server?

gordon.marler at gordon.marler at
Wed Dec 10 19:02:09 UTC 2008

Looking for conceptual guidance on a problem that has come up due to the
merging of two companies, each with different views on how to handle
DHCP (and DNS).

The goal is to have a newly built ISC DHCP server that gets the first
opportunity to respond to any and all DHCP queries.  We would like to
put IP Helper entries for this (and only this) DHCP server in all
routers in our infrastructure.  The DHCP will be configured to only
respond to clients that are already in DNS, and which have a known MAC
address/IP address/hostname mapping in the DHCP configuration (inserted
via OMAPI).  Seems an ideal case for "ignore unknown-clients".  This
DHCP server is solely intended to support Solaris/Linux OS installation
boots.  The configurability and availability of a usable API in ISC DHCP
is the driving factor for using it in this case.

We must, however, fall back to a pre-existing Microsoft AD/DHCP/DNS
server configuration in case the first ISC server cannot (and should
not) respond to a particular DHCP client.  This would include all
desktops and other clients that would be doing purely Dynamic DHCP/DNS

Said another way, we're really looking to configure ISC DHCP to
intercept ALL DHCP traffic, responding directly only to traffic it's
interested in (static DHCP, no DDNS), and forwarding/routing the
remaining DHCP requests to the Microsoft DHCP server.

Any guidance on how this might be approached would be appreciated.

Gordon Marler
gordon.marler at


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