Dual DHCP servers?

  • Thread starter Thread starter Fran
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Fran

I have two subnets running in an office. I want to allow DHCP to work
on them (e.g.
Network A = 192.168.20.xxx
Network B = 10.10.30.xxx

These are going through the same switch. Is it possible to have a DHCP
server for each address? If so, how do I administer/manage this?

<Fran>
 
You can do the whole thing with one DHCP. Create a scope for each Network
(*not* a Superscope). Configure the LAN Router that is sitting between the
segments to forward DHCP Queries from the clients in the opposite subnet to
the DHCP Server. Some routers will forward to the subnet the DHCP is in,
while some forward directly to the DHCP Server, while others can do it
either way.
 
If the relay is configured correctly, then the DHCP Server will be able to
determine from the forwarded DHCP message which scope to allocate an address
from, and the client will be given an address for the subnet from which it
came...

-Chris
--
==============================
Chris Edson
(e-mail address removed)

This posting is provided "AS IS" with
no warranties, and confers no rights.
===============================

Phillip Windell said:
You can do the whole thing with one DHCP. Create a scope for each Network
(*not* a Superscope). Configure the LAN Router that is sitting between the
segments to forward DHCP Queries from the clients in the opposite subnet
to
the DHCP Server. Some routers will forward to the subnet the DHCP is in,
while some forward directly to the DHCP Server, while others can do it
either way.


--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com


I have two subnets running in an office. I want to allow DHCP to work
on them (e.g.
Network A = 192.168.20.xxx
Network B = 10.10.30.xxx

These are going through the same switch. Is it possible to have a DHCP
server for each address? If so, how do I administer/manage this?

<Fran>
Click to expand...
Click to expand...
 
Thanks for the directions. I'm using Windows 2000 server to handle
routing using RRAS as my router (these are small networks with only 20
computers each but for legal reasons they must be on different subnets
to keep communications restricted.) Eventually I want to put all of
the networked printers on their own subnet as well but that's a
different issue ;)

I'm not sure I understand your directions well. I can create a scope
for each network on the DHCP server (especially since there are two
different domain servers running AD.) but the configuring the router
part has me a bit confused. Can you enlighten me with an example?
 
Thanks for the directions. I'm using Windows 2000 server to handle
routing using RRAS as my router (these are small networks with only 20
computers each but for legal reasons they must be on different subnets
to keep communications restricted.) Eventually I want to put all of
the networked printers on their own subnet as well but that's a
different issue ;)
Click to expand...

Having them on different subnets doesn't create any restrictions unless the
router can have ACLs, and even that doesn't cover it all and is not suitable
in all situations. The word "restricted" covers a large area of concepts and
what you actually want to restrict and why you want to restrict it
determines the method used and "Network Level" restrictions (routers, ACLs,
firewalls, etc) may not even be the right tool. There are also Application
Level Restrictions (IIS, MS SQL Server, MS Exchange Server, ect) and File
System Restriction (NTFS Permissions). The issues of "security" is a whole
industry out there and it just isn't that simple.
I'm not sure I understand your directions well. I can create a scope
for each network on the DHCP server (especially since there are two
different domain servers running AD.)
Click to expand...

AD and the number of Domain Controllers has nothing to do with it. DHCP is
a "network level" function and would work even if all you had was Unix
machines and not one single Windows machine or Windows Domain.
but the configuring the router
part has me a bit confused. Can you enlighten me with an example?
Click to expand...

Forwarding DHCP queries is a special router function. I don't know if RRAS
can do it or not. I'm not saying it can't,..I'm only saying I don't
know,...I don't use RRAS as a router here. Maybe others in the group can
answer that. Our router setup cost about $7000.00. Lower cost LAN Routers
that can still do the job might be between $1000 - $3000, but i don't buy
routers everyday so I may be off on the current prices.
 
RRAS Ip routing has an inbuilt DHCP Relay Agent which you need to configure.
It performs all the standard functions like listening and forwarding of
DHCP packets to servers. I am listing the major steps. Kindly consult the
RRAS help for details.

1.) Open up RRAS and expand "IP routing" . If the "DHCP Relay
agent" is not shown, right click on general and select "New Routing
Protocol". In the

display select "DHCP relay agent." The relay agent option
should now show up under "General" in RRAS.

2.) To add the 'listen on' interface, right click on "DHCP Relay Agent."
and select, "New Interface."

3.)The "New Interface for DHCP Relay Agent" dialog should now show up.

Select the proper interface to be used.

4.)Once done the Relay Properties display should appear

Make sure there is a check in the "Relay DHCP Packets." The "Hop-count
threshold." Is for the maximum number of DHCP relay agents that will handle
DHCP relayed traffic. Default is 4 the maximum is 16. (the default for this
value need not usually be changed) The "Boot threshold" is for the number
of seconds the relay agent waits before forwarding DHCP requests, to give
any 'local' DHCP Servers time to answer first.

5.) Now that the interface is added, we need to modify its settings to
specify which DHCP Server to send the relayed requests to. Right click on
the "DHCP

Relay Agent" and go to "Properties."

6.) The "Relay Agent Properties" display shows up.

Add the IP address of the DHCP server(s) to provide the service.
Click "Apply".

You're done.
 
RRAS IP Routing has an inbuilt DHCP Relay Agent which performs all the
standard relay agent functions like listening to client packets and
forwarding them to servers.I am listing the major steps to configure
it.Consult RRAS help for details.



1.) Open up RRAS and expand "IP routing" . If the "DHCP Relay agent" is
not shown, right click on general and select "New Routing Protocol". In the
display select "DHCP relay agent." The relay agent option should now show up
under "General" in RRAS.

2.) To add the 'listen on' interface, right click on "DHCP Relay Agent."
and select, "New Interface."

3.)The "New Interface for DHCP Relay Agent" dialog should now show up.

Select the proper interface to be used.

4.)Once done the Relay Properties display should appear

Make sure there is a check in the "Relay DHCP Packets." The "Hop-count
threshold." Is for the maximum number of DHCP relay agents that will handle
DHCP relayed traffic. Default is 4 the maximum is 16. (the default for this
value need not usually be changed) The "Boot threshold" is for the number
of seconds the relay agent waits before forwarding DHCP requests, to give
any 'local' DHCP Servers time to answer first.

5.) Now that the interface is added, we need to modify its settings to
specify which DHCP Server to send the relayed requests to. Right click on
the "DHCP

Relay Agent" and go to "Properties."

6.) The "Relay Agent Properties" display shows up.

Add the IP address of the DHCP server(s) to provide the service.
Click "Apply".

You're done.
 
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