Solved Some devices picking up the wrong IPs from DHCP server

September 4, 2014 at 02:14:17
Specs: Linux i686
I have a network of PC and laptops connected to a router and out to the internet.
I have the DHCP server in the router set to give out addresses from 192.168.1.100 to 200.

Up until yesterday everything worked just fine.

Today I've found several computers that could not connect out to the internet. I looked at the IPs and they were not in the range they should have been. Their IPs were 192.168.254.xxx and off course could not connect as this is a different network than the router altogether.

I made their IPs fixed in the right range (192.168.1.xxx) and they work fine.

Can't figure out why they are not picking the right IP????

Any ideas?


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#1
September 4, 2014 at 06:58:58
✔ Best Answer
Is this a wired or wireless network?
The only way a computer can pick up the wrong IP address is if some other computer or device is providing DHCP services. Such as another wireless router that is in range.

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#2
September 4, 2014 at 07:15:11
Yes, first check that you don't have another DHCP server in your network that the clients are connecting to and report back to us.

It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.

***William Henley***


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#3
September 5, 2014 at 00:34:16
Seems the router released the IP of the affected PC's. Is there any configuration in the router allowing/denying access of certain IP or MAC addresses?

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Related Solutions

#4
September 6, 2014 at 23:14:07
As far as I know there is no other DHCP server - the network is wired.
But..... I just found out right this minute that one of my colleagues put in a router "as a hub" somewhere in the network. She could not get into it to disable the DHCP server but installed it anyway. I think I may have found the problem.
I will chase that and get back to you guys. Thanks for your help.

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#5
September 6, 2014 at 23:54:59
Gawd! That was it. My colleague had connected an old router in the network to split one line between two computers as if it were a hub. Geez, not happy about it!

Now, if I turn off the DHCP server in it, would it do what she wanted?


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#6
September 8, 2014 at 13:38:45
Now, if I turn off the DHCP server in it, would it do what she wanted?

The simple answer is, yes.

First off, reset the unit to factory defaults.

If you google the make/model and something like "make/model manual" or "make/model setup guide" you should find the details on resetting it. Once it's reset, then you can access the management interface and do whatever you want......including disabling DHCP.

I would suggest you click on my name above in this response and read my “how-to” guide titled, “Add a second Router to your LAN

Pay attention to the scenario wherein you interconnect the two routers "LAN port to LAN port" and configure the second (downstream router) to be part of the network created on the first router. Definitely disable DHCP on it, it's not needed.

Also, I'd have a serious talk with whomever brought the equipment in to your environment without authorization. It could have got you hacked badly.

It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.

***William Henley***


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