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DHCP-problem

Posted on 1997-10-31
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Last Modified: 2013-12-23
Hi!

We have a network with a NT40-server (DHCP-server) and Windows 95-clients. We use TCP/IP as our primary network protocol, with IP-adress range 90.0.0.X.

In my job I have to do a lot of configuration changes on my office-PC, SCSI-card in/out, Soundcard in/out, Network-card in/out, etc...

A few days ago I changed my IP-adress to a static one while configuring a router. I later changed TCP/IP-properties back to "Get address from DHCP-server", but this would then not work any more.

I have now tried some things to get my PC fetch/lease the IP-address from the server, but are running out of options. The program "Winipcfg" doesn't help, I'm not able to renew the IP-address lease of my network card. I get an "DCHP-server not accessible..."-message. I have also tried serveral options (Reconcile, Refresh, Delete) in DHCP-manager on the NT-server, but this doesn't help. Why doesn't DHCP work?

When I configure my PC back to use a static IP-address, the problem is solved. I can then access the server in normal ways, and the "Ping"-utility works fine. When I use the DHCP-option, I get "Destination host unreachable".

Can anyone fill me out on this one, I'll be very grateful.
Thank You!
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Question by:riegsa
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Accepted Solution

by:
paulroberts earned 150 total points
ID: 1567075
There could be two things going on here. You mention that you were configuring a router? Is this something new? Does it sit between you and the DHCP server? If it does, you will need to configure a bootp/dhcp relay agent or forwarder (Cisco call it an ip-helper). This retransmits the DHCP messages from one subnet to the other. Routers block DHCP broadcasts by default, so you need the relay agent to forward it. Look in the router manual for instructions on how to set this up.

Alternatively, if it's not the router...

You mention that you do a lot of changes. If this includes lots of NIC changes, this could be the problem. Win95 keeps a record of the MAC address of each NIC you've had in that PC, but it can only store 8 MAC addresses. If you have put more than 8 different NIC's in this PC in the past, the registry key could be full up and DHCP will not work.

Check out the following registry entry...
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\DHCP

If you see keys labelled DhcpInfo00 through to DhcpInfo07 then it's full up. Use Registry Editor to remove all the keys except for the Dhcpinfo00 key.
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Author Comment

by:riegsa
ID: 1567076
Hi, PaulRoberts.

It's not the router, because it's not a part of the network on daily basis. And it's not the NIC-change either, because this affects all PC's in our network.

Today I turned on a PC that hasn't been in use for som time (about two weeks) and it has the same problem. The DHCP-function on the server seems to be the problem here.

Any ideas?
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Expert Comment

by:paulroberts
ID: 1567077
Hmmm, this sounds like a weird one, but it'll probably turn out to be something obvious! I think at this point I would start sniffing the wire. Have you got the Microsoft network monitor from SMS? This will decode DHCP packets fairly well. This should tell us if the server is responding or not.

Also, is there anything in the event log from the DHCP service?
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Author Comment

by:riegsa
ID: 1567078
The problem is solved!

The DHCP-service was "hung up"! I shut down the service and started it again and all worked fine.

But why was this service "hung up"? I have no explanation....

Thank you for your help, paulrobert. I'm still very satisfied with your answers!
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