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DHCP help.

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by joendosey

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Preface: I'm a rookie, so bear with me!
I am trying to set up our small LAN (200 computers) with private IP's. We are currently running NT4 on our servers and primarily Win98 on clients. All machines currently have static IP's. I have a solid theoretical understanding of DHCP, private addressing, NAT, etc... but this is my first "hands-on" experience. I have spent the better part of two days trying to get DHCP up and running. I have DHCP installed, but I am unable to set the scope. I initiallyset the range at 192.168.0.1-192.168.255.254 with a SM of 255.255.255.0. I get an error message stating that the scope either overlaps an existing scope, or is invalid. After fiddling with the numbers some, the scope was finally accepted and activated. I then used a test computer to logon to the network, which it did, but it did not get it's lease from DHCP, as a check on the server to all active leases shows none. (I assume the client computer used APIPA to obtain it's address.) I'm also unable to connect to the internet with this test computer. I need advice on specific steps to get DHCP working. I'm sure I am missing something along the way, and I know I probably did not provide enough info, so please request more if needed. Also, links to any useful self-help sites would be appreciated. Thanks.

5 replies

by joates

Joe,

Change your scope to 192.168.0.1 - 192.168.0.254 (more than enough IP addresses to handle your 200 computers) and change your subnet mask to 255.255.0.0 and you should be in good shape.

by malcolm r

Your original scope is being rejected since your subnet mask is incorrect. To use the network address range of 192.168.0.1-192.168.255.254 you need a /16 mask (255.255.0.0).

Have you configured the PC to pull its address from DHCP?

by timwalsh

You got the error because of a mismatch between the scope and the subnet mask.

A subnet mask detemines what part of the IP address is the network address and what part of the IP address is a node address. With a subnet mask of 255.255.255.0, youare saying that the first three octets are the network address. Yet you are also saying the network address will vary from 192.168.0.0 to 192.168.255.0. This just won't work.

You need to do one of two things:

Keep the same subnet mask and change your scope to 192.168.0.2 - 192.168.0.254 (192.168.0.0 is your network address; you need one IP address for your router and one IP address for the network broadcast address (this is always x.x.x.255)). This gives you a possibility of 253 possible host IP addresses.

Keep the scope and change your subnet mask to 255.255.0.0. However, this gives you a possibility of approximately 65,000 host IP addresses (a bit overkill for 200 workstations).

By the way, once a scope has been created, the only way to change the subnet mask is to delete and recreate the scope.

If you need more than 253 IP addresses in a single network segment, you are getting into the subject if subnetting (which you REALLY don't want to get into here.

by joendosey

Thanks for the replies, but unfortunately, still not working. I cannot determine if the problem lies in the DHCP service on the server, or if it is a problem on the workstation. I have set up two win98 computers and both have the same problem. What should I look at on the server end to ensure the DHCP service is running smoothly? On the workstation end, aside from setting it to obtain its IP automatically, what other settings are necessary? What do I use as the gateway; the static, public IP ofthe router, or am I supposed to use a number from the scope? What about DNS? Do I enable or disable on the workstation and let DHCP configure? Thanks again for taking the time to input suggestions.

by joates

Joe,

You should have two services running on the server: DHCP Server Service and DHCP Client Service.

You will have only the DHCP Client Service running on the workstation. It has been so long since I configured a W98 client, I can't remember if there is anything else on that OS but I don't think so.

As long as you have DNS running on the server, there should not be an issue connecting that with DHCP failure to assign an IP. Even having a gateway is not necessary to automatically assign an IP.

Good luck!

Joe

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