Running new dhcpd instance on same physical interface

[David W. Hankins]

On Sun, Mar 15, 2009 at 12:08:46AM -0500, Frank Bulk wrote:
> It would be atypical for a service provider to run a separate instance of
> DHCP for each type of service.

It is.

But I don't remember seeing this part of the thread before, so I
wanted to make a quick reply to this part;

> I will appreciate very much if you have a better idea or another suggestion
> on how to resolve this without adding another physical interface that in
> fact it will be connected to the subnet that the other one.

Provided all of the server activity is IP unicast, there is a (seldom
used, often broken, and poorly documented) way to build the DHCP
server to "USE_SOCKETS" (#define in includes/site.h).  With this build
method, the server can not be guaranteed to be RFC 2131 compliant in
messages it can receive or transmit (raw sockets work around that for
us).

But, provided USE_SOCKETS was used, the "local-address" configuration
parameter becomes available, so the single dhcpd instance may be bound
(as through the bind() system call) to a specific IPv4 address,
possibly an alias address.  Take care to also configure the server's
server-identifier option identically.

In this manner, a single box can house any number of DHCPv4 server
instances differentiated by IPv4 addresses.

I can't go into any greater detail than that, so good luck.

-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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