multi-homed DHCP problems

[Guest]

Server is a Win2k AS that is acting as a DC, DHCP, DNS (duh) and file server.
It has two NICs in it, each on a different subnet (192.168.1/24 and
192.168.2/24). The DHCP server appears to be correctly configured with a
superscope and the correct address pool bound to each IP.

It has been running and providing DHCP for a couple of years with no
problems. Now, it is beginning to assign addresses from one subnet to
machines on the other. It doesn't do this all of the time, and it doesn't do
it with machines that have been connected the whole time, only new machines
or machines moved from the other subnet.

Has anyone seen a problem like this before, and, even better, has anyone
solved a problem like this before?

 

[Herb Martin]

Server is a Win2k AS that is acting as a DC, DHCP, DNS (duh) and file server.
It has two NICs in it, each on a different subnet (192.168.1/24 and
192.168.2/24). The DHCP server appears to be correctly configured with a
superscope and the correct address pool bound to each IP.

It has been running and providing DHCP for a couple of years with no
problems. Now, it is beginning to assign addresses from one subnet to
machines on the other. It doesn't do this all of the time, and it doesn't do
it with machines that have been connected the whole time, only new machines
or machines moved from the other subnet.

It sounds like the subnet mask on the DCHP server
itself may be in error, or the one(s) on the Scopes.

Check your IPConfig against the two scopes.

Has anyone seen a problem like this before, and, even better, has anyone
solved a problem like this before?

I don't think so, this would be a pretty serious bug
so it is likely a misconfigured DHCP (NIC->IP)
Server or a mistake (in one of) the scopes.

 

[Phillip Windell]

Server is a Win2k AS that is acting as a DC, DHCP, DNS (duh) and file server.
It has two NICs in it, each on a different subnet (192.168.1/24 and
192.168.2/24). The DHCP server appears to be correctly configured with a
superscope and the correct address pool bound to each IP.

It has been running and providing DHCP for a couple of years with no
problems. Now, it is beginning to assign addresses from one subnet to
machines on the other. It doesn't do this all of the time, and it doesn't do
it with machines that have been connected the whole time, only new machines
or machines moved from the other subnet.

Has anyone seen a problem like this before, and, even better, has anyone
solved a problem like this before?

Yes. I have seen it when people use Superscopes when they aren't supposed
to. You should have separate distinct Scopes,..no Superscopes. The server
will hand out IP# from the Scope that corresponds to the subnet of the
Interface it received the "query" on. Make sure your subnets do not "share
the wire" anywhere (like pluging hosts from two subnets into the same switch
without VLAN'ing).

Another method to use would be to run the server with one nic and just the
one IP# that it is supposed to have. Use a LAN Router between the LAN
Segments and config the Router to forward the DHCP Queries to the DHCP
Server. The DHCP Server will know how to give the right IP# from the right
Scope without having to do anything extra.