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Message-ID: <4490A0D3.E4E18727@teksavvy.com>
Date: Wed, 14 Jun 2006 19:50:56 -0400
From: JF Mezei <jfmezei.spam...@teksavvy.com>
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Newsgroups: vmsnet.networks.tcp-ip.ucx,comp.os.vms
Subject: Re: Multi-homed DHCP server
References: <e6ph2q$1ks$1@charm.magnus.acs.ohio-state.edu>
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"Michael T. Davis" wrote:
>         A few weeks ago, we added an interface in TCPIP to provide access to
> a secondary subnet which resides on our network.

I am on VAX with older version (but since Join no longer exists, I
suspect no much has been done with the DHCP server).


If you look at the TCPIP$DHCP_RUN.LOG , you'll see that when it lists
its configuration, it has and option to ignore a list of interfaces. Not
sure if this is accessible from the DHCP$GUI interface, but it is
probably configurable if you go into the actual text config files.

Note that a DHCP CLIENT sends a broadcast from a bogus IP address. Any
DHCP server on that ethernet segment can reply to it (also as a
broadcast because at that point, the client still doesn't have an IP address).

So, from the DHCP Server point of view, it can discriminate between
clients based on:
	-their ethernet address (MAC)
	-some host name their desire (included in the request)
	-or which physical interface the broadcast is coming from.

In your case, since you have multiple IP subnets on the same ethernet,
the DHCP server has no logical way to know if a request is coming from a
PC supposed to be on one subnet or another.


If you do a NETSTAT, do you see port 67 being listened on on each
interface ?

(On my system, it is strange, it listens on the cluster alias, on the
main interface as well as *.67 and the TCPIP service is defined as
listening to 0.0.0.0 (which results in the NETSTAT *.67 and
automatically listens to any IP interface).