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DHCP Problem

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11 replies

by macarcher

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We have two networks separated by a T1 line with Cisco 1600 routers at each end. It is one Domain with the PDC on the 192.168.1.x network running a DHCP server and a BDC on the 192.168.2.x network also running a DHCP server. I have some users that when they receive an IP number from the DHCP server on the 192.168.2.x network, I cannot ping the other network. However, if I assign an IP number to them, I can ping the 192.168.1.x network. The DHCP server is a BDC that is also a WINS replication partner on the other side of a T1 line. The PDC is on the other side of the T1 line on the other network. The settings for the DHCP are the same as when I assign a static IP number (WINS, gateway, DNS servers). They are getting an IP number from this DHCP server as ipconfig /all shows. In fact ipconfig /all shows the same settings no matter which method is used. Any ideas as to why this is happening?

11 replies

by donalconlon

There may be a dhcp helper address on the routers which is pointing to only one of the dhcp servers

by macarcher

It seems that one client who I didn't switch back to a static IP address is not having a problem. He can browse the other network with no problems. The client who cannot browse is using a laptop while the other is using a minitower. The laptop is running WIN98 while the other is running WIN95.
Thanks for the help though.

by sgremor

As was stated before check the helper addresss, but also check your subnet masks.

by james.pounds

You may want to double check your DHCP scope's assigned default gateway specification and make sure it designates the nearest Cisco router as the default gateway.

by macarcher

After all this started I did check the DHCP server's gateway address and it is correct. That seems to the logical solution but I have another client using the DHCP server that can ping/browse the other network. I am starting to believe that it is the IP protocol stack on this particular client.

by mckaytech

When you say you can't ping, do you mean you can't ping at all even by using an IP address or that you can't ping using a NetBios name? The first is a connectivity problem; the second is a name resolution problem and the solution is different.

Also, what happens when you ping the workstation IP itself and then the gateway address on the 2.x network?

If you can't ping the workstation's own IP address, the most usual conclusion is that the TCP/IP stack is hosed and needs to be re-installed. That's a pretty common fix for a lot of these bizarre problems that don't make sense.

However, if you can ping the gateway but not to the other side, it's typically a routing issue although I can't explain why it would work for a static addressthat is the same as the DHCP address for which it doesn't work.

paul

by macarcher

I cannot ping the other network from this client. I can ping within the network with no problems. You may be right. The IP stack may need to be reinstalled. This is not something I am looking forward to as he has a Japanese version of Win98.
Thanksfor your time, I do appreciate the help.

by gijoe

You need to find out what the difference is in the client computer that does not have any problem with this when he's using dhcp. There may be a LMHOSTS or HOSTS file in that computer that is being used. Check your WINS and DNS servers.

by macarcher

The problem seems to occur when he takes the computer home and hooks it up to his cable modem. When he brings it back to the office, then the problems start. This is now moot as he purchased a computer for home.

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