Another device on the network is using your computer's IP address

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Level 1

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Another device on the network is using your computer's IP address

Another device on the network is using your computer's IP address

I receive this error message all the time now. It starting about a year or so ago, and occurred perhaps once a week. Now it happens many times per day, as much as ten times.

Network is DSL modem --wired---> airport extreme

connecting devices include a macbook pro (snow leopard), imac 24" (Lion), ipod 1, PS3, apple tv 2nd gen, and an airport express for streaming music.

The problem is with the imac computer. When it sleeps, and reawakes, it has lost its IP address. I need to unplug the extreme and restart it.

I have simplified the network to only the computer, and it still happens. I cannot see if some device is causing the problem.

It is not a neighbour logging in to my network.

This was never a problem, then with the Leopard/snow leopard, it started to occur. With Lion, it is all the time now.

All my settings on the modem and airport are as they should be, and have been for the last several years.

The only hint from google searchs was the Bridge mode setting on the airportextreme. I did try to change this, but it would not let me do so.

Google seems to return many people having similar problems, so there is something happening to more than just me.

Any suggestions?

iMac, Mac OS X (10.7.1)

Posted on Sep 14, 2011 4:50 PM

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Answer 1

Tesserax

Level 10

148,453 points

Sep 14, 2011 11:42 PM in response to Andrew Beney

The only hint from google searchs was the Bridge mode setting on the airportextreme. I did try to change this, but it would not let me do so.

If the AirPort Extreme Base Station (AEBS) is connected directly to the DSL modem by Ethernet, why has it been reconfigured as a bridge? Is this DSL modem, just modem, or a combination modem & router or gateway device? Regardless, what is its make & model?

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Answer 2

Andrew Beney Author

Level 1

20 points

Sep 15, 2011 11:15 AM in response to Tesserax

The modem is a 2wire modem, with the number 3800HGV-B on it. One ethernet goes to the AEBS, and the other to the digital tv box. I do know that it is the modem that connects (PPOE) to the provider. When we installed the system, we had to switch the AEBS from where it was to bridge in order to get online. It worked fine until just recently (see above).

I did try to change to "share addresses" but it comes up with a box that says "The DHCP range you entered conflicts with the WAN IP address of your Apple Wi-Fi base station", and it want me to enter in a beginning address and an ending address. Since i am not that familiar with networks, I didn't want to start changing things around too much.

I feel that the problem is here somewhere, but we (ie the digital tv install people) had to switch the airport to a bridge to get things working.

I think this is a gateway device as there are several ethernet ports availble, and it can broadcast a wi-fi signal (which is turned off).

Does that give you more to go on?

Thanks

Andrew

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Answer 3

Tesserax

Level 10

148,453 points

Sep 15, 2011 4:40 PM in response to Andrew Beney

Ok, this 2Wire device is definately a gateway (combination modem and router). In their default configuration, both the 2Wire and the AEBS would have both NAT & DHCP enabled and this would introduce certain issues. Typically, you would want the downstream router, i.e., the one connected to another that is directly connected to the Internet modem, to be in bridge mode. Thus why, most likely, the digital TV installer had reconfigured the AEBS in bridge mode.

With the AEBS as a bridge, the 2Wire would provide both NAT & DHCP to all network clients, regardless of which actual router they are connected to. In addition, the 2Wire is providing your user credentials (username & password) via PPoE to your ISP.

Ok, with that said, every network client, including the AEBS, must be configured as DHCP clients. For the AEBS or Macs, that would be the "Using DHCP" setting either in the AirPort Utility or System Preferences > Network respectively. There is a possiblity that just one of the network clients is not configured as such and when the DHCP server in the 2Wire hands out IP addresses, it is not being dynamically updated ... and thus, the potential reason for the IP address conflict warning.

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Answer 4

Andrew Beney Author

Level 1

20 points

Sep 15, 2011 5:17 PM in response to Andrew Beney

HI, thanks for that info. Paragraph 1 I understand, and confirms what I thought happened with the install. Paragraph 2 makes sense, and yes the modem does the handshaking. Now paragraph three, as far as I can tell all machines (especially the problem iMac) are set to use DHCP. Now the ipod, apple tv, and PS3 do not have that setting (to my knowledge) they just connect to the network.

So I left feeling that everything is where it should be, but it ain't working.😕

Any other suggestions? It wasn't that bad until about a month ago. Now it is constant. Nothing has changed! (actually, the modem was powered off. Would powering down and turning on the modem cause this situation? I don't think it should.)

Thanks for any thoughts

Andrew

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Answer 5

Tesserax

Level 10

148,453 points

Sep 15, 2011 8:16 PM in response to Andrew Beney

The 2Wire router's built-in DHCP Server should provide private IP addresses in a certain range. I would use the 2Wire's web-based adminstration interface to verify what this range is. Then, double-check each of the DHCP Clients to: 1) See if they are in this range, and 2) To see if any have been assigned the same IP address.

I would also suggest the following:

Reassign a static private IP address for the AEBS. Be sure that it is just outside of the 2Wire's DHCP range. It's always a good idea to assign static IP addresses to routers, wireless access points, printers, NAS boxes, etc, so that they can always be "found" by network clients.
Temporarily do the same for the problematic iMac.
Leave all other network clients as DHCP clients.

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