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Strange DHCP occurrence

By kdbtech ·
Currently in my small business I run a single DHCP server for my 200 clients on a Windows 2000 server (non DC). In an attempt to switch this service to a Server 2003 server (DC) I run into a problem. The service installs fine and once configured will give out addresses all day, but every address received from this server only will not go out past the firewall.
I have checked and rechecked the gateway address, DNS server addresses and even arghhhh. WINS, but everything is fine. If I attempt to switch from dynamic to static using the same information received from the dhcp server, I can gain my external access back again.
The server has a single network card that is configured as an adapter correctly in the dhcp service and will give out addresses fine.
My plan is to eventually reformat the original dhcp server and use it for redundancy, however I must get the new one working first (obviously!) Any help here would be great.

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by coucha In reply to Strange DHCP occurrence

If the old server was working, try Microsoft's KB Article #325473. That article shows how to export the DHCP Database from a Windows 2000 to a Windows 2003 Server.

http://support.microsoft.com/default.aspx?scid=kb;en-us;325473

Hope that helps!

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by kdbtech In reply to

OK, this is the guy that worked. It would appear the the transferrence of the actual database was required rather than just the configuration script which I imported first. After following the information in this article, my DHCP server worked!

Thanks coucha!

Kevin

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by CG IT In reply to Strange DHCP occurrence

In an attempt to understand, you say your DHCP server gives out ip addresses to clients but said addresses don't go past the firewall. Well if they are private non routable addresses, they won't. You need NAT running which adds a header to the packet with the public routable IP address.

If its a configuration problem e.g. clients need an IP address, subnet mask, default gateway and DNS for internet connectivity, you provide that to clients via options. These are the options most commonally configured for clients. 003 router if you have one. 005 for name servers if you have those or 006 for DNS servers.

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by kdbtech In reply to

No, I understand the concepts of NAT perfectly fine and my firewall is handling the process correctly. My issue seemed to be strictly with DHCP and coucha grabbed the answer I needed. Thanks for your help!

Kevin

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by softcorp.us In reply to Strange DHCP occurrence

Hello...

DHCP typically assigns IP addresses like 192.168.*.* to PCs. By convention, these addresses are private to a LAN and are not routed over the Internet. Likewise, such addresses cannot be seen from the Internet either. Note: There are other address ranges that work this way also.

Such PCs can _use_ the Internet if you have a NAT router (Network Address Translation). But, they cannot be _used_ by systems on the Internet because they are private now. In Windows terms, NAT is called "Internet Connection Sharing".

For a PC on your LAN to be seen on the Internet, it must have a public IP address. As you know, if it is behind a firewall, the firewall must allow the desired traffic to pass through.

Did this information help with your problem? Please supply any additional information needed so I can better focus this answer.

-----Steve Jackson

CEO/CSA
Software Corporation (Softcorp)
http://www.softcorp.us/probono
Advanced pro bono tools and utilities free for personal use

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by kdbtech In reply to

Sorry, I thought that by trying to place as much information in the question I would eliminate answers which did not apply. Sorry to say that ICS is just not happening in my workplace of 300 users and my firewall is handling NAT fine so my header translation is working correctly. Apparently my solution was to completely import the database file into the new server using a process specific to Windows Server 2003. Thanks for your time!

Kevin

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by kdbtech In reply to Strange DHCP occurrence

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