DHCP Server not leasing in his own range

[SaMaLaKo]

Hi all,

Recently we moved our DHCP service from ancient Windows NT4 Servers to new Windows Server 2003 servers.
These 2 DHCP servers are each located in a different site acting as hot backup for each other, and leasing IP's for about 20 scopes for different subnets.
All DHCP relay/IP helpers are set-up in our Cisco switches.
Each DHCP server is authorised in Active Directory and working perfectly for all scopes except for the scope in the same subnet he is located in.

To make it clear:
DHCP Server IP: 192.168.25.25/24
DHCP Scope: 192.168.25.50 --> 192.168.25.100
Other systems connected to that subnet and configured for DHCP do not get a DHCP lease from the DHCP Server

This is realy freaking me out!
I have no clue how to troubleshoot this.

Anybody a suggestion?



Please tell me if I'm wrong I like to learn from my mistakes...
_____________________________________
Feed a man a fish and feed him for a day.
Teach a man to fish and feed him for a lifetime...

 

[theravager]

I've seen some weird things with dhcp from migration projects. Clients getting leases from scopes that are disabled etc.

One particular issue i found which was happening a while back to a few subnets was only fixed by manually deleting the lease out of dhcp while the client was powered down. I have also seen a few where you actually had to manually release the ip on the client and powerdown and then manually delete reservation in dhcp.

 

[SaMaLaKo]

OK, I'm really stuck here.
I did some testing to rule out the network part.
What I did:
- Made sure the DHCP service was running.
- Disconnected the server from the corporate network.
- Connected the server to a hub.
- deactivated all scopes except the scope for the local subnet.
- Connected a DHCP client to the hub and waited for an IP address.
--> Nothing happened!!!
The client did not get an IP !!!

This means the error is somewhere located on the server itself, but where?



Please tell me if I'm wrong I like to learn from my mistakes...
_____________________________________
Feed a man a fish and feed him for a day.
Teach a man to fish and feed him for a lifetime...

 

[theravager]

This might be obvious but is the dhcp server ip in the same range as what the scope is that the hub is connected to?

 

[SaMaLaKo]

The servers ip: 172.23.14.21/24
The scope: From 172.23.14.50
To 172.23.14.80

Please tell me if I'm wrong I like to learn from my mistakes...
_____________________________________
Feed a man a fish and feed him for a day.
Teach a man to fish and feed him for a lifetime...

 

[theravager]

Pretty sure dhcp won't work while it cant see a dc to authorise dhcp starting, its been a while since i have fiddled around in that scenario thou so i maybe wrong.

Check that theres no ip helper address configured on the local vlan. Other then that i think you are going to have to fire up a network sniffer and see what is going on as everything sounds ok

 

[benso37]

Delete the scrope and recreate it. Are you excluding any range of IPs? Do you have a firewall that's capable of blocking unknown DHCP Servers? Under scope options, do you have your router defined?

 

[SaMaLaKo]

The DHCP service was already started before I disconnected it from the network to do the test with the hub. So it already contacted the DC to determine if it is authorised.
But apparently it needs to see the DC on a very regular base. (with every ip offer?) so this test is not a good one.

On all VLAN's the IP-Helper address is configured except for the VLAN where the DHCP server is located.

I recreated the scopes several times.
Not excluding any IP from any scope.
No firewall
And all scope options have been defined (Router, DNS, WINS, TFTP,...)

Thanks for all the input, but no solution so far...


Please tell me if I'm wrong I like to learn from my mistakes...
_____________________________________
Feed a man a fish and feed him for a day.
Teach a man to fish and feed him for a lifetime...