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	[x] Attachment Details

How To Find DHCP Server On Network

Zones: Networking Hardware, Miscellaneous Networking, Network Management

Tags: dhcp, find, server, how, network

Hello,

We have a network composed of:
1 Linksys Router
2 Linksys Wireless Access Points (Not Routers)
2 16-port 10/100 switches

We recently needed to open a port on the router, and did not have the password so we reset the router and reconfigured.

The issue is this; before we reset the router, we handled addresses through DHCP (on that router) handing out addresses 192.168.0.XXX. The router's IP is 192.168.0.200.

After we reset the router, it defaulted to an IP 192.168.1.1 and the DHCP scheme was 192.168.1.XXX. We changed the router's IP to 192.168.0.200 and the DHCP scheme updated automatically in the router configuration.

The problem is, DHCP is still being served on the 192.168.1.XXX scheme. According to a client connected to the network, the DHCP server is 192.168.1.1. If I pin 192.168.1.1 I do get a response. I can also ping 192.168.0.200 which should be the address of the router.

Unfortunately I cannot power cycle or disconnect any network component until the weekend, since this is a doctor's office that needs maximum uptime. To get everyone up and running, I setup static IP address on each computer.

I plan on going in tomorrow when the office is closed and troubleshoot further. My first step will be to connect a laptop only to the router and see what IP I receive. I suspect that the main router is not the culprit. It does not make sense that I can ping both 192.168.0.200 and 192.168.1.1.

When I attempt to go to the configuration pages:
http://192.168.0.200 brings me to my router's configuration page
http://192.168.1.1 says page not found
A port scan of 192.168.1.1 yields no open ports

Assuming the router is not the problem, something else on the network must also be handing out address via DHCP, and for some reason is taking precedence.

Does anyone have any suggestions on this issue. Am I correct in thinking some other device on the network must be causing the problem? Is it possible that the router could exist at two IP address, both able to be pinged? If it is another device, can you think of any better way to identify it than by simply pulling cables out of the switches one at a time? I've tried a port scan, name lookup, nothing yielded a result.

Thanks for the advice.

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Question Stats

Zone: Computer Hardware

Question Asked By: compsol1993

Solution Provided By: Brugh

Participating Experts: 5

Solution Grade: B

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Open Discussion

Comment by OrcaKnight

Just a note: Because you have wireless routers, you might consider that someone else was piggy-backing on your network when you reset, and still had thier systems connected to yours, until the latest post. That would, in light of the lack of any other DHCP server in your known network, explain the sudden gain of a phantom, pingable device.

20080723-EE-VQP-34 / EE_QW_2_20070628