Client not getting DHCP addresses from server

Recently we had a small power outage where the evironment went down for about 2sec and then came back up. The Domain controller (DHCP server..... Win2K3 standard) was on a UPS so nothing happened to it. how ever when the clents (all Win XP Pro) came back up the couldn't get a address from the DHCP server. I tried rebooting them (clients and the Server), but that didn't help. I tried shutting down the DHCP client and DHCP server service on both the server and client and restarting them, but that didn't help. I dont know what could be wrong.  DHCP server has more than 90% free IP address to dole out. Made sure the service is authorized and scope is activated on the Server . Any suggestions ??? Everything was fine before the power out
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Any chance the switch went bad or possibly lost its configuration?
this is what i do when this happens.

1.  restart the computer

when you are back in the network
2.  assign static ip and start pinging the server (to make sure the network card is not burnt)

If you are able to ping the network by assigning static ip to the client computer.
3.  remove the client computer from the domain
4.  re-join the domain
5.  remove the static and enable DHCP

Home that help you man.. because it help me a lot!  ;)
Any events logged in system or application? Both clients and server.
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judeadesouzaAuthor Commented:
Just checked the events logs. Doesn't state anything extraordinary related to DHCP. The service seems to be up and running on the server. My best guess is the switch. Could it be that the switch is preventing DHCP broadcast from the server??? I cant reset the switch because everyone is a twork right now. i will have to do this in the afterhours. But, I just want to confirm with everyone if this could be the reason.

I have yet to try pstrawsers solution. But that would be very tedious cause we have over 130 systems on the network
If all 130 systems are having the same problem, removing them all from the domain is not the best solution.  It also has nothing to do with the problem given that they'll likely need IP information to accomplish such a feat :)

Would suggest double checking the DHCP server as well.  Make sure it can ping the clients and vice versa.  If everyone is still connected it's probably not the switch.
Also, can you confirm if the clients and DHCP server are on the same switch.  If not, how are they linked? VLAN information?  If everyone is still happily connected (until their leases expire) I'm leaning more towards a problem with the DHCP server itself.  Network card, bad cable, switch-port, something.  What's connectivity to/from that system like?  Everything normal?  Any chance the windows firewall is messing with you?

Also - try running a sniffer like Wireshark on one of the clients and running an "ipconfig /renew" and see if you get any broadcast response back at all.

let me get this one straight.. so you are saying.. 130 people are having the same problems or just one computer?  this solution is for one workstation only..    just assign static ip to make sure that it is not the switch or the nic card.    if you are not able to ping the servers then you know it's the card or switch..  
judeadesouzaAuthor Commented:
Well.....most of the systems on our network were assigned static IPs about 3 month ago because of a problem we had we out old DHCP server. we moved over to a new server about a month ago and it was working fine till friday when we had the power outage. Now since most of my pcs are with static IPs, its not a major problem, but there a few systems that were given dynamic in the hope of having all of them eventually moved to DHCP.
All the clients can connect to the server as well as go out to the internet. The only problem is that they are not able to get dynamic IPs. For now those with dynamic IPs are given static IPs, but I eventually want all system to be dynamic. I tried testing all those machine (with dynamic IPs) by rebooting, running ipconfig/ renew. but it doesn't seem to work. When the server went down friday, the System logs said the NIC card connected back at 100Mbps / HalfDuplex. I find that odd cause shouldn't it be full duplex

Also I just cheched the logs again and found something wierd that I missed before. About an hour after the power outage, the event logs gave the following error

" The DHCP/BINL service on the local machine, belonging to the Windows Administrative domain aaaaaa.local, has determined that it is not authorized to start.  It has stopped servicing clients.  The following are some possible reasons for this:
      This machine is part of a directory service enterprise and is  not authorized in the same domain.  (See help on the DHCP Service  Management Tool for additional information).

      This machine cannot reach its directory service enterprise and  it has encountered another DHCP service on the network belonging to  a directory service enterprise on which the local machine is not authorized.

      Some unexpected network error occurred. " (event ID 1045)

About 20 seconds later it gave the following message

"The DHCP/BINL service on the local machine, belonging to the Windows Administrative domain aaaaaa.local, has determined that it is authorized to start. It is servicing clients now.

For more information, see Help and Support Center at" (event ID 1044)

Any suggestions. I dont have any other DHCP server running the network
Probably safe to try verifying the credentials:

Load DHCP Snap-In | right click server | properties | Advanced tab | Credentials button | re-enter domain admin user/pass etc. | click OK | restart DHCP | check event log

Also - check the properties on the network adapter and check to see if it's set to auto negotiation or manually configured to something else.
judeadesouzaAuthor Commented:
Hey matt l

I tried verifying the dhcp credentials.... like you said above and also unplugging and replugging the NIC.... But it didn't help. I'm still not able to get dhcp address from the server... any other suggestions.

Another problem that could be related is the DNS is not servicing certain users for some reason. we have an enviroment where user use roaming profiles and some user can't get certain local web application resolved with  the server. I have to manually edit their host file to to include the address. I stopped the DNS service for both client and server, but that didn't help

This problem also started after the power out on friday. I don't know whats wrong and could the problem be related. Everybody is able to access the server for file shares and other stuff. The server seems to be functioning.

Any suggestions????
Are you sure that there are no other DHCP servers other than yours? What network devices (switches, routers, ...) are between your server and clients that are not getting the IP address?
This looks really weird.

For DNS problems I do this (on client):
1. ipconfig /flushdns
2. restart DHCP Client
3. ipconfig /flushdns

These steps usually solve all dns problems on windows (my domain, not a common solution)
... so if you assign static ip, the work station can ping the server right?

uninstall dhcp server and re-install .. make sure all configuration is correct and remove the static ip and restart the workstation and see if it can find the dhcp server....
judeadesouzaAuthor Commented:
Hey All

Here the situation right now. DHCP is still  not working. It is running on the server, but clients are not getting DHCP IPs. Hence clients have been given static IPs and DNS is pointing to this sever. DNS is also acting funky. Sometimes client are not able to resolve computer names. They are able to get out to the internet, but when try to resolve computer name of another server (say server A) which hold IIS based application. It won't resolve. Its like the DNS server is not servicing DNS request for this client. But if I go to another computer, it manages to resolve A, it works with out a hitch. I happens to random computer on the network. After a while these computer will work fine and another computer will give problems. All users have roaming profiles.

I ran wireshark protocol analyser on both client and server to resolve the DHCP issue. On client it broadcast DHCP request to see who can service it but on server, it doesnt seem to see the client broadcast for DHCP request which is kinda funny. Both client and server are on the same switch. There is no firewall on client and server.

Another funny thing is that certain clients managed to retain their DHCP address even after the power out that we had last friday. They still able to renew their IPs

I ran an NMAP port scan on the server to see if UDP port 67 and 68 (client and Server ports for DHCP) were open. NMAP returned that they were open but filtered. I dont know what that means. But Packet scan on the server shows not DHCP client request

I hope all this makes sense. Can Someone please help

judeadesouzaAuthor Commented:
hey Everybody,

I finally figured what was causing the problem we were having. apparently one of the switches we were using took a hit from the the power fluctuations. It was alayer 3 switch and hence somehow started blocj DHCP and sometime DNS request to the server. I replaced the switch and things were back to normal.
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