DHCP multiple subnets

[Jeniffer K]

Dear NG, here is another one...

We have a W2k3 server setup in a school acting as a DC, File server and
DHCP, the server is obviously not connected to the internet because we need
to make sure that no student has access to the web, not psychically nor
technically even DHCP is configured to hand out blank gateways, we want
however to have the ability to manage and support the server remotely so we
decided to attach the second nic to the administration network (on a
separate DC also providing DHCP) which has a DSL line, here is what im
thinking of doing it...

* the student subnet on nic one is 192.168.20.x
* the administration subnet on nic two is 192.168.1.x
*DHCP on the student server has a scope of 192.168.20.100-192.168.20.199
* Routing and remote access is disabled on the student server

*NIC config on the student server*
NIC 1 - Stdent network
IP= 192.168.20.250
SM= 255.255.255.0
GW= empty!
DNS = 192.168.20.250

NIC 2 - Administration network
IP= 192.168.1.250
SM= 255.255.255.0
GW= 192.168.1.1
DNS= ?

when preforming a quick test i ened up having a few machines in the
administration office with an ip of192.168.20.x (obviously causing it to
lose network connection to their own server) because it was picking up DHCP
from the wrong server, can I tell DHCP to respond to DHCP request only on
NIC 1 and if not any other recommendations?

thanks

 

[Doug Sherman [MVP]]

On the student server open the DHCP console; right click the server and
select Properties. Click the Advanced tab - Bindings button. DHCP should
be bound only to the 192.168.20.250 adapter.

Doug Sherman
MCSE, MCSA, MCP+I, MVP

 

[Jeniffer K]

Thanks Doug, and if I ever decide to configure the student server to hand
out DHCP (guess ill have two scopes) to both subnets and administration
wouls that be possible so that if your attached to the 1.x nic you should
obtain a 1.x address and if you're attached to the 20.x subnet it should
give you a 20.x address

 

[Doug Sherman [MVP]]

Yes, you can do that, and it is common practice for purposes of
redundancy/failover. However, it is important that you split the scope by
excluding different portions of the address range on each DHCP server:

http://support.microsoft.com/kb/280473/en-us

Another thought - Right click My Network Places and select Properties.
Click Advanced and select Advanced Settings - make sure the Local Area
Connection for the 192.168.20.250 NIC is at the top of the binding order.
Sometimes when you add a second NIC to a server the new adapter winds up at
the top of the binding order and this can make a domain controller behave
very strangely.

Doug Sherman
MCSE, MCSA, MCP+I, MVP

 

[Jeniffer K]

yeah but i'm talking about two different subnets, so is it possible to bind
a scope to a nic

 

[Doug Sherman [MVP]]

OK, I didn't answer your real question - YES, you can create a second scope
(192.168.1.x); bind DHCP to both the 192.168.20.250 NIC and the
192.168.1.250 NIC; and the server will automatically hand out addresses from
the correct scope to clients on the respective networks. No further
configuration is necessary.

What I was talking about was what happens if you do the above and leave the
existing 192.168.1.x DHCP server in place. In that situation, you would
want to split the 192.168.1.x scope between the two 192.168.1.x DHCP servers
in order to avoid conflicts.

Doug Sherman
MCSE, MCSA, MCP+I, MVP

 

[Jeniffer K]

thanks Doug

OK, I didn't answer your real question - YES, you can create a second
scope
(192.168.1.x); bind DHCP to both the 192.168.20.250 NIC and the
192.168.1.250 NIC; and the server will automatically hand out addresses
from
the correct scope to clients on the respective networks. No further
configuration is necessary.

What I was talking about was what happens if you do the above and leave
the
existing 192.168.1.x DHCP server in place. In that situation, you would
want to split the 192.168.1.x scope between the two 192.168.1.x DHCP
servers
in order to avoid conflicts.

Doug Sherman
MCSE, MCSA, MCP+I, MVP