IP Address Conflict ?

D J Hales wrote:
When starting up my MacBook the following dialogue box occasionally appears - "*Another device on the network is using your computer's IP address (192.168.03).* Try connecting again later. If you continue to have problems, change the IP address of this computer or the IP address of the other device. Contact the network administrator if you need more information."
The only other computer on the network is my wife's iBook G4 and the above problem arises even when that is switched off !
Only by shutting down and then re-starting the MacBook can I satisfactorily connect to the internet.
Can anyone explain what is happening here ? Many thanks.

As the message says, another device on your network is using the IP Address (btw and not that it matters I don't think you typed the address correctly above).

Are you sure your network is using DHCP to assign addresses? Are you sure no devices on your network have manually assigned IP Addresses? If you don't have another device on the network then maybe a neighbor is connecting to it and getting that address when you have manually assigned that address to your MacBook.

Describe your network. Do you have a router? If not, what device is assigning IP Addresses to your and your wife's computer? How are you connected to the Internet?

With the most common setup (dhcp). IP addresses are assigned by the router. Essentially the router is saving that IP for your computer. We your computer goes to sleep some routers have been known not to realize the computer is sleeping and thinks the computer is still connected. When the computer wakes and tries to connect to the router, the router tells the computer, this IP is not yours and belongs to another computer even though it was on the same IP, and the same computer.
Have no fear their really isn't anything wrong with your computer, it's the router kinda getting temporary confused.
Instead of restarting the computer try renewing the dhcp lease on the computer, the router will then assign a new IP to the computer.
Another option to avoid this issue is to use dhcp with manual IP (aka static IP), where you specifically assign an IP to you and your wife's computer.

Hope this all makes sense for you.

I'd be interested in knowing the model router that is causing the behavior you cite. I've never run across these behavior in more than 25 years providing IT and Network support. That is not to say the issue is not out there but only that I have never run across it. If this is indeed what is happening I'd suggest that the OP ensure their router's firmware is current.

DHCP should not care whether the computer is sleeping or indeed turned off. The DHCP RFC says that DHCP should try to reassign the same IP Address previously assigned to a device, unless the device has been disconnected (asleep) for longer than the DHCP lease and the IP Address has been re-assigned to another device.

Regardless, your advice to try renewing the DHCP lease is good but a pain to have to do each time. Maybe a router firmware upgrade will resolve the issue.

2Wire router for me. It's been giving me non-stop problems for the last year. And yes, the router software is up to date.

When I used to have my AppleTV set to a DHCP address, it was constantly reassigning my Mini's IP to the AppleTV, causing a conflict. Now that I set the AppleTV to a manual address, my Mini just looses internet connection until I ask for "DHCP with manual address" and plug in a different address.

It's really frustrating.

Jabrwock,

I know very little about networks, but for what it's worth, I had the same problem and finally found a solution when I called Applecare. I have a 2Wire router and I had a time capsule plugged into it in bridge mode. I also used an airport express to extend the network by pairing it to the time capsule. The 2wire would assign the same IP address to the time capsule as the IP address on my computer and then I wouldnt be able to get on the internet and I would restart the computer or time capsule to get it back to normal. This happened about once every 2 days.

What worked was extremely simple: The applecare guy had me go into airport utility and go to time capsule-->internet-->internet connection-->connection sharing and then change the time capsule setting from "bridge mode" to "share a public IP address" and then update...I have had no problems since then and everything is working perfectly so it seems.

I have no idea why this has worked so well because I really dont understand most of the terminology and what is going on as I am just a beginner in understanding networking, but it is working very well.

Hope that works for you.