Server 2000 DHCP
I'm trying to help someone configure some new computers on their network and am having issues with DHCP. They are running Server 2000 which is set up to be the DHCP server for their network. They have a few computers that are part of the domain and one computer running XP that is not set up as part of the domain. Those computers are working fine. When I try to add a new system to the network, they are not able to pull an IP address and get the error that they cannot connect to the DHCP server. I've checked the server there are 50 available IPs in the DHCP range and they only have about 10 devices on the network. The new systems are running Vista and XP. If I manually assign an IP outside of the DHCP range, the computers are able to access the internet. I've checked the configuration on the XP system that is working and can't see that there is any unusual network configuration. Any advice would be greatly appreciated.
May 31st, 2011 1:14pm

This could be network related. Is there anything in common with the computers that are unable to obtain an IP lease...maybe a different VLAN with no Relay Agent for that VLAN? Did you check the DHCP logs on the server to see if the DHCP service did receive the lease request, but just responded with a NACK (negative acknowledgement)?Visit: anITKB.com, an IT Knowledge Base.
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May 31st, 2011 1:23pm

Hello, this sounds like connectivity problems between the computer and the DHCP server, how exactly are they connected, all on one switch or are routers in between? Please be more specific.Best regards Meinolf Weber Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.
May 31st, 2011 1:56pm

Hello, it looks like a connectivity problem like other suggested. Please use a static IP address and check if you are able to ping the server. If yes then I think that all is okay with your routes. Also, please check that there is no network component that is blocking DHCP traffic. You can use Wireshark to sniff DHCP traffic. Also check DHCP log files and see if there is logged errors. If yes, please post them here. This posting is provided "AS IS" with no warranties or guarantees , and confers no rights. Microsoft Student Partner 2010 / 2011 Microsoft Certified Professional Microsoft Certified Systems Administrator: Security Microsoft Certified Systems Engineer: Security Microsoft Certified Technology Specialist: Windows Server 2008 Active Directory, Configuration Microsoft Certified Technology Specialist: Windows Server 2008 Network Infrastructure, Configuration Microsoft Certified Technology Specialist: Windows Server 2008 Applications Infrastructure, Configuration Microsoft Certified Technology Specialist: Windows 7, Configuring Microsoft Certified IT Professional: Enterprise Administrator
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May 31st, 2011 2:34pm

Thanks everyone for the feedback. I will check the DHCP logs and post what I find here. The network has one switch and all of the devices are connected directly to it except for a couple areas that have a second 4 port switch to connect additional devices. In those areas, the second switch is connected directly to the main switch. They have a modem and router connected to the main switch and DHCP is turned off so there's no conflict. I can't think of anything that the computers that cannot connect have in common. Three are running Windows Vista and are connected to the main switch directly and one is running XP and is connected to a 4 port switch then directly to the main. The systems have very little software installed, in fact I think the vista machines only had one piece of software installed (software to display charts; nothing to do with networking).
June 1st, 2011 8:12am

I would suggest checking DHCP scope if there are free IP addresses in pool. This can be caused that DHCP pool has not enough IPs to serve. Additionally, please check if there are no excluded IPs within this scope. It can also prevent issuing IP addresses. Can you verify it, please? Regards, Krzysztof
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June 1st, 2011 9:08am

I was able to check the scope are there are 50 available IPs and only about 10 devices on their network. No IPs are excluded.
June 1st, 2011 3:11pm

Hi, Thanks for posting here. Could you also confirm if the main switch is a 3<sup>rd</sup> layout switch device ? what’s the model? Thanks. Tiger Li Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.
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June 2nd, 2011 1:35am

The main switch is a Cisco SR224G. I think this would have to be some type of issue on the server. I'm going back today to check the DHCP logs and will post what I find.
June 3rd, 2011 9:05am

I have this issue worked out, but I'm not sure what the root cause was or how to prevent it in the future. I had originally stated that all the IPs weren't assigned because looking at the DHCP leases, there were only about 8 devices listed. When I looked at the status for the DHCP range though, it showed all 50 were used. I increased the DHCP range, and everything is now working fine. How would I fix this in the future without increasing the range? It seems like this is something that's likely to reoccur.
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June 6th, 2011 11:44am

Hm, strange, looks like some problem with DHCP database (?) Maybe there was something wrongly released within that database. Can you run DHCP management console on that server, select appropriate scope and click Right Mouse Button (RMB), choose "Reconcile" from context menu and click on "Verify" button. Do you see "The database is consistent" message or you received information that some entries were released? Maybe server was rebooted unexpectedly and DHCP database was corrupted? Regards, Krzysztof
June 7th, 2011 4:52am

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