DHCP problem

[stevefar]

we have a small network (230 windows98 clients) nt4 pdc, nt4 bdc(x2) DHCP installed and working with ip address range is 192.168.0.1 to 192.168.3.254 subnet mask 255.255.252.0 the servers have static ip address and everything is working.
until now ,we have added 30 new computers (win98) to the network and find that they cant get the ip address from the server.
Any ideas

 

[SmittyNMCI]

There may be a few things to look at here. 1st, check the router to see if the ports are set up properly for the additional workstations. If you are sure that they are then try configuring 1 workstation with a static IP address in the range of your DHCP scope along with the gateway, DNS and WINS if used (I would assume that a WINS server is used if 98 is being deployed). This will also show that the router is indeed set up. If the workstation connects then check your workstation configuration for DHCP and/or your DHCP server for scope configuration. From first guess though I would look hard at the router.

Hope this helps
Smitty
A+ Network+ MCSA MCSE

 

[stevefarrow]

Hmmm we dont have a router, i thought that all the ip address were on the same subnet and as such we would not need a router. is this correct? or have i miss understod.....

Thanks

 

[SmittyNMCI]

You are correct. You don't need a router unless you are bridging to another subnet. I just assumed that you had one. Having a router or not does not really change the problem so lets do a bit of troubleshooting.

I see that a private IP scheme is being used and that you have a gateway (the bdc being used as a DHCP server). Assuming that the workstations are configured the same as the 230 that work, leaves me to wonder about the common connection point of the 30 new workstations.

A bit of information about the topology would help but one of two things that you can do to narrow this down would be to configure one of the 30 non working workstations with a static IP address (one you know is not being used) and gateway (the DHCP server) in the scope provided and see if it connects. The other would be to connecting a known working workstation using the cable of the known not working workstation and see if it obtains an IP address. The first seems simpler to me. If it connects then you know the problem lies in the configuration of the 30 workstations or the DHCP server. If it still does not connect then the problem lies in the connection of those 30 workstations to the network. This might be a common switch/hub or the cable connecting this switch/hub to the rest of the network. I personally find it hard to believe that all 30 NICs would be a fault but it might be the installation/configuration of those NICs if they were all installed/configurated the same though I would still tend to rule this out as configering a NIC for DHCP is pretty straight forward.

Hope this helps some.

Jeffery Smith (Smitty)
PEC Solutions Inc.
A+ Network+ MCSA MCSE

 

[stevefarrow]

Some good points, don’t think it’s the hubs/switches or the network cable, looking on the net it seems I could have a DHCP server fault, so what I might do is uninstall the DHCP server, reinstall it apply sp6 again and see if it fixes the problem,what do you think? I kind of get the feeling that the problem is at the server side of things, true about the nics I could see 3 or 4 out of 30 being duff but not all 30.
Our network is quit simple as shown below each room has a switch / hub with computers connected.

Server1(PDC) Server2(BDC) etc
|
|
Switch / hub
|
|
room1 room2 room3 room4 room5 etc

 

[SmittyNMCI]

I hesitate on thinking that it is the DHCP server for the reason that the other 230 computers get their leases renewed unless you have permanent leases set. This would tell me that the DHCP server is functioning as it resends the IP at the renewed lease request. If one of the working 230 computers fail to get their lease renewed then I would look at the DHCP server. However, the static IP address would still rule out or for that matter prove a connectivity problem quicker and easier than reinstalling the DHCP service. Good luck with this.

Jeffery Smith (Smitty)
PEC Solutions Inc.
A+ Network+ MCSA MCSE

 

[stevefarrow]

hi just turned on the room with the new computers and they can all connect and logon to the domain!! (the hubs and cable are all working all are getting ip addresses assigned from the DHCP server (so that’s also working) but the DHCP server seems unable to issue ip addresses greater than 192.168.0.243 so when I try to put more computers on the network I will run out of Ip addresses, now this is frustrating.
DHCP server setup:
Scope 192.168.0.10 to 192.168.3.240 netmask 255.255.252.0
No reservations at all now.
I have put the servers and such in the first 10 ip addresses.
Will keep you posted as to how it goes
Thanks for all the help so far it’s been good to share my pain and frustration

 

[SmittyNMCI]

This is most definitely an interesting problem. You are correct in that the problem has been proven to be the DHCP service. Mathematically speaking it does not make any sense as to why it stops at 243. This would equate to 11110011.

I am curious as to why you have chosen to run a class C private scheme (the private I do understand) and then supernet it instead of just running a class B private scheme (172.16.0.0 - 172.31.255.255) and then subnetting (mask 255.255.252.0 for range 172.16.0.0 - 172.16.3.255). Not that it makes any difference here, just curious. As far as I understand DHCP, it does not make any difference what the numbers are, it just does the math.

I am now thinking that your original suggestion would be the more correct solution of uninstalling DHCP service and then reinstalling it. See if the math can now be done. I would be curious as to what finally corrects this situation. Keep me posted.


Jeffery Smith (Smitty)
PEC Solutions Inc.
A+ Network+ MCSA MCSE