DHCP Changes DNS Only

J

jwgoerlich

Under what conditions would a Windows XP station dynamically request a
DNS server entries only?

I ask because I have workstations that use DHCP. Sometimes, these only
update the DNS entries. The previously configured IP address, subnet,
and gateway does not change.

Thanks in advance,

J Wolfgang Goerlich
 
C

Chuck

Under what conditions would a Windows XP station dynamically request a
DNS server entries only?

I ask because I have workstations that use DHCP. Sometimes, these only
update the DNS entries. The previously configured IP address, subnet,
and gateway does not change.

Thanks in advance,

J Wolfgang Goerlich
Click to expand...

One possibility would be if "Use the following IP address" were selected in the
IP settings wizard.
<http://nitecruzr.blogspot.com/2006/08/manual-network-setup-procedures.html>
http://nitecruzr.blogspot.com/2006/08/manual-network-setup-procedures.html

Otherwise, I'd suspect LSP / Winsock corruption.
<http://nitecruzr.blogspot.com/2005/05/problems-with-lsp-winsock-layer-in.html>
http://nitecruzr.blogspot.com/2005/05/problems-with-lsp-winsock-layer-in.html
 
J

jwgoerlich

Hello Chuck,

Hmmm. The workstations are setup for DHCP and thus the "Use the
following IP address" option is unchecked. Winsock seems alright though
I can reset it. See, there are two DHCP servers, one on each subnet.
Some workstations get an IP address on subnet A and a DNS entry on
subnet B.

It seems that either: a) the workstations received their IP address
from one DHCP server and their DNS entry from another; or b) the
workstations requested a new DNS entry after a while.

J Wolfgang Goerlich
 
C

Chuck

Hello Chuck,

Hmmm. The workstations are setup for DHCP and thus the "Use the
following IP address" option is unchecked. Winsock seems alright though
I can reset it. See, there are two DHCP servers, one on each subnet.
Some workstations get an IP address on subnet A and a DNS entry on
subnet B.

It seems that either: a) the workstations received their IP address
from one DHCP server and their DNS entry from another; or b) the
workstations requested a new DNS entry after a while.

J Wolfgang Goerlich
Click to expand...

Well, "ipconfig /all" will show, at any time, what DHCP server provided
settings. One server at a time - and all dynamic settings from the same server,
at that time.

Do you have 2 subnets on the same physical segment? With a DHCP server for
each? If so, there's the problem. Why do you need two logical segments,
randomly assigned?
 
J

jwgoerlich

Yes, ipconfig /all shows the DHCP settings. The IP Address, Subnet
Mask, Default Gateway, and DHCP Server all come from one of the DHCP
servers. Yet, strangely, the DNS Servers entries come from the other
DHCP server.

I would not have thought this possible. The only thing that I can
figure is that the Windows XP computer made two separate DHCP queries.
This is why I am asking for the conditions that would cause an XP box
to request only the DNS server entries.

J Wolfgang Goerlich
 
C

Chuck

Yes, ipconfig /all shows the DHCP settings. The IP Address, Subnet
Mask, Default Gateway, and DHCP Server all come from one of the DHCP
servers. Yet, strangely, the DNS Servers entries come from the other
DHCP server.

I would not have thought this possible. The only thing that I can
figure is that the Windows XP computer made two separate DHCP queries.
This is why I am asking for the conditions that would cause an XP box
to request only the DNS server entries.

J Wolfgang Goerlich
Click to expand...

If you have examined "ipconfig /all", and it truly shows a computer having
gotten settings from 2 different DHCP servers, then I would check again for LSP
/ Winsock corruption, but more thoroughly. Note that there are several
different LSP / Winsock repair procedures, and none of them are more effective
than the others.

Or I'd re examine the evidence. Does this split server assignment happen
repeatedly? On multiple computers? How often? The same computer repeatedly?

Maybe post "ipconfig /all" logs here for third party intrepretation. A set of 3
logs. One from a problem computer, a second from a computer properly serviced
by server A, a third from a computer properly serviced by server B. Maybe
examine the DHCP logs from servers A and B.

And once again, why not tell us why you need 2 subnets on the same physical
segment, that you allow to exist simultaneously, yet have random membership.
Maybe that's part of the problem.
 
J

jwgoerlich

Does this split server assignment happen repeatedly?

It happened once.
On multiple computers?
Click to expand...

Yes, three computers out of five lab workstations.
How often? The same computer repeatedly?
Click to expand...

Once. I haven't tried repeatedly.
Maybe post "ipconfig /all" logs here for third party intrepretation.
Click to expand...

I'll drop them in at the end of this message.
And once again, why not tell us why you need 2 subnets on the same physical
segment, that you allow to exist simultaneously, yet have random membership.
Click to expand...

I do not need two subnets on one segment, nor two DHCP servers. It was
a mistake in the lab. What struck me as incredibly curious was that the
workstations split the addressing. That is, I would have expected some
workstations to get an IP from first DHCP server and maybe others to
get an IP from the second. Instead, three of the computers obtained the
IP from the first DHCP and the DNS from another.

Thought maybe this would be a simple question to those more familiar
with XP (I normally work on 2003). I'll have to set this back up and
try to duplicate the symptom.

J Wolfgang Goerlich


Ipconfig /all, from my notes. The first DHCP server is 192.168.10.9. It
also provides DNS and WINS. The second rouge DHCP server is 192.168.1.1
and it provides DNS. Note that the lease is from the first and the DNS
is from the second.

Ethernet adapter Broadcom Connection:

Connection-specific DNS Suffix . : lab1.jwgoerlich.us
Description . . . . . . . . . . . : Broadcom NetXtreme 57xx Gigabit
Controller
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.10.213
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.10.1
DHCP Server . . . . . . . . . . . : 192.168.10.9
DNS Servers . . . . . . . . . . . : 192.168.1.1
Primary WINS Server . . . . . . . : 192.168.10.9
Lease Obtained. . . . . . . . . . : Wednesday, September 13, 2006
10:50:31 AM
Lease Expires . . . . . . . . . . : Friday, October 13, 2006 10:50:31
AM

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . : lab1.jwgoerlich.us
Description . . . . . . . . . . . : Broadcom NetXtreme 57xx Gigabit
Controller
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.10.204
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.10.1
DHCP Server . . . . . . . . . . . : 192.168.10.9
DNS Servers . . . . . . . . . . . : 192.168.1.1
Primary WINS Server . . . . . . . : 192.168.10.9
Lease Obtained. . . . . . . . . . : Wednesday, September 13, 2006
10:14:07 AM
Lease Expires . . . . . . . . . . : Friday, October 13, 2006 10:14:07
AM

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . : lab1.jwgoerlich.us
Description . . . . . . . . . . . : Broadcom NetXtreme 57xx Gigabit
Controller
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.10.211
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.10.1
DHCP Server . . . . . . . . . . . : 192.168.10.9
DNS Servers . . . . . . . . . . . : 192.168.1.1
Primary WINS Server . . . . . . . : 192.168.10.9
Lease Obtained. . . . . . . . . . : Wednesday, September 13, 2006
11:09:31 AM
Lease Expires . . . . . . . . . . : Friday, October 13, 2006 11:09:31
AM
 
C

Chuck

It happened once.


Yes, three computers out of five lab workstations.


Once. I haven't tried repeatedly.


I'll drop them in at the end of this message.


I do not need two subnets on one segment, nor two DHCP servers. It was
a mistake in the lab. What struck me as incredibly curious was that the
workstations split the addressing. That is, I would have expected some
workstations to get an IP from first DHCP server and maybe others to
get an IP from the second. Instead, three of the computers obtained the
IP from the first DHCP and the DNS from another.

Thought maybe this would be a simple question to those more familiar
with XP (I normally work on 2003). I'll have to set this back up and
try to duplicate the symptom.

J Wolfgang Goerlich


Ipconfig /all, from my notes. The first DHCP server is 192.168.10.9. It
also provides DNS and WINS. The second rouge DHCP server is 192.168.1.1
and it provides DNS. Note that the lease is from the first and the DNS
is from the second.
Click to expand...

Is your DHCP server a NAT router? I thought that you had a domain, and a real
server. So your problem is actually with 3 computers in a lab, using a NAT
router. And the problem happened once.

Well I use a NAT router too, but not for DHCP. Maybe you could peruse the DHCP
logs on both servers? Might give you a picture of what happened. Beyond that,
let it happen again, and check the logs.
 

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