Q&A: MacFixIt Answers

MacFixIt Answers is a feature in which we answer questions e-mailed in by our readers.

This week people wrote in with questions on how to tackle an IP address conflict error, an issue with Apple's Hardware Test suite not loading, and whether or not Time Machine backups need to be started from scratch when attaching the local Time Machine disk to an Airport Extreme router. We welcome alternative approaches and views from readers, so if you have any suggestions or alternative approaches to these problems, post them in the comments!

Question: Tackling a duplicate IP address error
MacFixIt reader James asks:

Yesterday, on booting up my Mac Pro running Lion with patched (original patch) Office, I got an alert I had never seen. I forgot the exact message text, but the gist of it was: "Your Mac Pro address is used by another device". Sophos Anti-Virus (up-to-date) revealed no threats; I did nothing. Today on launch I did not get the message again. Could this have been caused by an Office-malware-attack?

Answer:
This situation is because of a network misconfiguration and nothing more. Your home router issues IP addresses to your computer and other devices on the network, and should keep track of the addresses given to each device, but sometimes there are errors (especially if someone has manually adjusted IP settings) where two devices are given the same address. When this happens, if your computer is one of them, then you will see this error show up. Generally the problem gets fixed automatically, but if it persists, then ensure all devices on the network are set to use "DHCP" or "Automatically obtain an IP address." You can also try resetting your router to clear the problem.

Question: Apple Hardware Test suite not loading on a Mac Pro
MacFixIt reader Gabriel asks:

No matter what I try the [Apple Hardware Test] does not load. I just bought a MacPro 3.33 GHz 6-Core Intel Xeon, 32 GB 1333 MHz DDR3 ECC and it keeps dismounting one of the Hard Disks. I have never had problems with this Hard Disk until I got the MacPro. I sent it back to Apple and they repaired [some parts], yet the disk keeps getting dismounted so I spoke with the people at the Apple Store and they said it must be the disk. However, it works fine on other computers but after installing in bay 4 of the MacPro, it sooner or later will get dismounted for no reason.

This is why I need the Apple Hardware Test, so that maybe I can find out what is wrong but for some reason it will not load.

Answer:
The hardware tests should be included on new systems, so you can simply hold the "D" key at startup to load them. However, to load the tests from the Internet you will need to press Option-D at startup and ensure your system has an Internet connection (an Ethernet connection will ensure this is the case).

If none of these options work, then you will need to take the system in to have these tests performed, as these are the only options you have to run the hardware tests. However, before you do, you might try the drive in a different bay to see if it will stay mounted. If so, then the problem is likely a hardware issue.

Question:
MacFixIt reader Michael asks:

I've recently purchased an Airport Extreme Router. I currently have my Time Machine backups on a Seagate Go Flex external hard drive, which is hooked up directly to my iMac. I want to move this external drive and hook it up directly to the AE to do my backups. Main reason is I want to use this drive to do my backups for my Macbook Pro as well, which I just bought.

I unplugged the drive from my iMac, and hooked it up to the router. After going through the setting for Time Machine on my iMac, it started to back up, however, it wanted to back up everything again.

Is there any way I can set this up where it won' t have to back up the whole iMac again (were talking 500GB here)?

Answer:
There is no way to prevent the need to fully back up again when you switch the drive setup like this. Time Machine via the AirPort Extreme will create a disk image file for each computer that uses it, whereas when directly connected to the system Time Machine writes directly to the drive instead of to a disk image. There is no way around this.

Your best bet to ensure you make full use of your Time Machine drive is to format it and then set it up on the AirPort Extreme, followed by setting up each system to back up to it, and then waiting for the entire backup to occur.

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