2 DHCP's on one network???

Hi All,

First my question;

What harm can having 2 DHCP servers on my small network
do?(28 clients, 3 servers, 2 switches, 1 firewall)
Can it cause clients to lose connection to thier servers,
corrupt data, cause wierd error messages?

Now my problem;

We're running 3 DC's, 2) W2K and 1) W2K3. Clients have
been receiving "Disk or Network error" messages while in
an Access database or wierd "rlzt.run" messages while in
our accounting software Accpac.

I've checked the event viewer on all clients experiencing
the problem and noticed under the System log that they
all have this error in common;

Event ID : 1002

"The IP address lease 10.0.0.173 (this varies of course)
for the Network address (MAC address) has been denied by
the DHCP SERVER 0.0.0.0 The DHCP server sent a DHCPNACK
message."

Last night I noticed that we have 2 DHCP servers on our
network. The vendor who installed our network and
hardware configured our FIREWALL to act as a DHCP server
(scope 10.0.0.70 to 10.0.0.139, 60 minute lease) and they
configured our FILE SERVER (W2K SP4)(scope 10.0.0.100 to
10.0.0.200, 1 week lease) to act as a DHCP server.

From the research i've done thus far, it appears that
only one DHCP server should be live on my network.
I've stopped the DHCP service on the FILE SERVER and at
this time only the FIREWALL is serving as DHCP.

This has been plagueing our company for some time now,
any help you can provide will be GREATLY appreciated!!
Even more so, because we're about to switch our business
software from Accpac to Great Plains and I don't want
these problems to happen in our new software.

robertj

"robertj" <(E-Mail Removed)> wrote in message
news:d2b401c439c1$9a688930$(E-Mail Removed)...
> First my question;
> What harm can having 2 DHCP servers on my small network
> do?(28 clients, 3 servers, 2 switches, 1 firewall)

Nothing if done properly

> Can it cause clients to lose connection to thier servers,

Yes

> corrupt data, cause wierd error messages?

Corrupt data, no,....weird errors, maybe yes

> Last night I noticed that we have 2 DHCP servers on our
> network. The vendor who installed our network and
> hardware configured our FIREWALL to act as a DHCP server
> (scope 10.0.0.70 to 10.0.0.139, 60 minute lease) and they
> configured our FILE SERVER (W2K SP4)(scope 10.0.0.100 to
> 10.0.0.200, 1 week lease) to act as a DHCP server.
>
> From the research i've done thus far, it appears that
> only one DHCP server should be live on my network.
> I've stopped the DHCP service on the FILE SERVER and at
> this time only the FIREWALL is serving as DHCP.

As long as they don't each try to give out the same addresses you would be
fine. forexample:

DHCP #1 grants 10.0.200.1 through 10.0.200.254
Exclusions 10.0.200.128 through 10.0.200.254

DHCP #2 grants 10.0.200.1 through 10.0.200.254
Exclusions 10.0.200.1 through 10.0.200.127

Additional Exclusions (identical on both) 10.0.200.1 through 10.0.200.10

Each DHCP Servers gives out half of the possible addresses. Both of them
exclude and don't use the first 10 addresses whic allows these first 10 to
be used for static assignments to other Servers and such.

However I would ditch the DHCP on the Firewall and stay with the Window's
DHCP(especially if running two) since it is more flexable and you have more
control over it.


--

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

Thanks Phillip!!

I do have one more question.

I'm following through on your suggestion by shutting down
the FIREWALL DHCP and using the Windows DHCP. My
question is, which server do you recommend using as the
DHCP?

My FILESERVER is a W2K box, 1 Xeon processor, 1.5 ram,
plenty of storage.

My EXCHANGE server has the same spec's., except it has
W2K3 standard and Exchange 2003. Both see a fair amount
of traffic. I know that installing DHCP on either box
will effect performance. However I would like to use the
EXCHANGE box, for the enhancements to DHCP in W2K3.

Do you have any estimates on how much of a drag this will
have on my mail server?

Thanks for your insights,
robertj
>-----Original Message-----
>"robertj" <(E-Mail Removed)> wrote in
message
>news:d2b401c439c1$9a688930$(E-Mail Removed)...
>> First my question;
>> What harm can having 2 DHCP servers on my small network
>> do?(28 clients, 3 servers, 2 switches, 1 firewall)
>
>Nothing if done properly
>
>> Can it cause clients to lose connection to thier
servers,
>
>Yes
>
>> corrupt data, cause wierd error messages?
>
>Corrupt data, no,....weird errors, maybe yes
>
>> Last night I noticed that we have 2 DHCP servers on our
>> network. The vendor who installed our network and
>> hardware configured our FIREWALL to act as a DHCP
server
>> (scope 10.0.0.70 to 10.0.0.139, 60 minute lease) and
they
>> configured our FILE SERVER (W2K SP4)(scope 10.0.0.100
to
>> 10.0.0.200, 1 week lease) to act as a DHCP server.
>>
>> From the research i've done thus far, it appears that
>> only one DHCP server should be live on my network.
>> I've stopped the DHCP service on the FILE SERVER and at
>> this time only the FIREWALL is serving as DHCP.
>
>As long as they don't each try to give out the same
addresses you would be
>fine. forexample:
>
>DHCP #1 grants 10.0.200.1 through 10.0.200.254
>Exclusions 10.0.200.128 through 10.0.200.254
>
>DHCP #2 grants 10.0.200.1 through 10.0.200.254
>Exclusions 10.0.200.1 through 10.0.200.127
>
>Additional Exclusions (identical on both) 10.0.200.1
through 10.0.200.10
>
>Each DHCP Servers gives out half of the possible
addresses. Both of them
>exclude and don't use the first 10 addresses whic allows
these first 10 to
>be used for static assignments to other Servers and such.
>
>However I would ditch the DHCP on the Firewall and stay
with the Window's
>DHCP(especially if running two) since it is more
flexable and you have more
>control over it.
>
>
>--
>
>Phillip Windell [MCP, MVP, CCNA]
>www.wandtv.com
>
>
>.
>

Phillip,

I just reread your reply. Scratch my earlier query.
You've already answered it. I can use BOTH the FILESERVER
and EXCHANGE server as DHCP, just be mindful of how I
allocate the scopes and exclusions on each.

But I guess that still leaves the question of
perfromance? Your thoughts?

Many thanks again,
robertj

>-----Original Message-----
>"robertj" <(E-Mail Removed)> wrote in
message
>news:d2b401c439c1$9a688930$(E-Mail Removed)...
>> First my question;
>> What harm can having 2 DHCP servers on my small network
>> do?(28 clients, 3 servers, 2 switches, 1 firewall)
>
>Nothing if done properly
>
>> Can it cause clients to lose connection to thier
servers,
>
>Yes
>
>> corrupt data, cause wierd error messages?
>
>Corrupt data, no,....weird errors, maybe yes
>
>> Last night I noticed that we have 2 DHCP servers on our
>> network. The vendor who installed our network and
>> hardware configured our FIREWALL to act as a DHCP
server
>> (scope 10.0.0.70 to 10.0.0.139, 60 minute lease) and
they
>> configured our FILE SERVER (W2K SP4)(scope 10.0.0.100
to
>> 10.0.0.200, 1 week lease) to act as a DHCP server.
>>
>> From the research i've done thus far, it appears that
>> only one DHCP server should be live on my network.
>> I've stopped the DHCP service on the FILE SERVER and at
>> this time only the FIREWALL is serving as DHCP.
>
>As long as they don't each try to give out the same
addresses you would be
>fine. forexample:
>
>DHCP #1 grants 10.0.200.1 through 10.0.200.254
>Exclusions 10.0.200.128 through 10.0.200.254
>
>DHCP #2 grants 10.0.200.1 through 10.0.200.254
>Exclusions 10.0.200.1 through 10.0.200.127
>
>Additional Exclusions (identical on both) 10.0.200.1
through 10.0.200.10
>
>Each DHCP Servers gives out half of the possible
addresses. Both of them
>exclude and don't use the first 10 addresses whic allows
these first 10 to
>be used for static assignments to other Servers and such.
>
>However I would ditch the DHCP on the Firewall and stay
with the Window's
>DHCP(especially if running two) since it is more
flexable and you have more
>control over it.
>
>
>--
>
>Phillip Windell [MCP, MVP, CCNA]
>www.wandtv.com
>
>
>.
>

"robertj" <(E-Mail Removed)> wrote in message
news:d40a01c439db$3b13f040$(E-Mail Removed)...
> I'm following through on your suggestion by shutting down
> the FIREWALL DHCP and using the Windows DHCP. My
> question is, which server do you recommend using as the
> DHCP?

Basically just one that runs :-)
I run both of mine on a pair or P2 350's (Server2003) and each one is also
the DC, WINS, and DNS as well. They are identically configured (except where
it would cause conflicts) so that either one can act as the sole DC, DNS,
WINS, DHCP if the other dies,..one can keep me afloat until the other is
fixed. They are not "sceamers" but do fine, but I don't sit at them and use
them like a workstation either. I just leave them alone and let them do
their jobs. I don't think DHCP creates much load, but I don't have any
"numbers" for that.

--

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

robertj wrote:
> Phillip,
>
> I just reread your reply. Scratch my earlier query.
> You've already answered it. I can use BOTH the FILESERVER
> and EXCHANGE server as DHCP, just be mindful of how I
> allocate the scopes and exclusions on each.
>
> But I guess that still leaves the question of
> perfromance? Your thoughts?

I'm not Phillip, but my thoughts would be for this amount of clients then
DHCP services shouldn't be a terrible burden for any of the servers you
list, unless you have some reason to set the lease expiry to a very short
period of time.
--
--
Rob Moir, Microsoft MVP for servers & security
Website - http://www.robertmoir.co.uk
Virtual PC 2004 FAQ - http://www.robertmoir.co.uk/win/VirtualPC2004FAQ.html

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