IP Address is already in use???

Who controls your local network?

I'm trying to understand if you can change how IP leases are handled or clear out everything that's currently assigned in DHCP.

Did you provide your own router?

Do you by chance have an ipad, a NAS or a network printer?

If you're able to, check your logs on your router. Otherwise check your DHCP table, IP reservation list and any static IPs on your network that may be causing the conflict.

whyyes said:

So funny story, yesterday afternoon I tried opening the internet and it has worked 100% of the time. No issues. I don't know what was going on, but thankfully its over. : ) Thanks for the help!

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I'd actually be a bit more worried about this. If this is your private router & network, then it may indicate that someone else is accessing it.

I actually had this same problem last week.

My wireless connectivity is a bit dodgey (a router problem, or so I believe) and has a tendency to drop in and out every once and a while.

This error message regarding duplicate IP addresses popped up a couple of times during "problem" wireless periods. My assumption was that the laptop lost wireless connectivity during a period during which the router re-allocated that IP address to another device.

Either that, or when the laptop returned to the network the router didn't recognise it as the same device that was last using that IP Address. I can't imagine why that would happen though.

Anyway I've set up a static IP Address for the laptop (note to self, turn this off when I travel next week!), and thus far it hasn't happened again.

Thus far.

I had this problem as well. I am a computer professional so it caught me as strange that the problem even occurred. I think it may be a bug or something because no one has access to my network and there were only two machine with IP's...the range isn't long enough and it was secured with WPA.

Edit: I should say the problem was fixed with some ip releasing/renewing and restarting the router. No problems since.

To be honest, I had problems too and all my connections started to have problems at different times. First it was our main PC, then my mobile, then Wii... etc. It only started when I got my MBP and the Time Capsule. At the end I made 3 IP reservations on the router, 2 for the MBP (wired and wireless) and 1 for the Time Capsule. Since then everything has been running trouble free *touch wood*.

I'm experiencing the same problem here. I have a macbook, a macbook pro and an Iphone. The wifi on the iphone and macbook work but not on the pro. It has given me the same error message once but most of the time it recognizes the router but the internet doesn't work. I've tried renewing the lease, tried different ip addresses that are similar or the same to my iphone (this just messed up my iphone which thankfully work again after I forgot the network). The wifi works on other networks but not my home network.

Any ideas?

Hah this happens (used to happen) with me all the time when I was in university a short while ago. Don't rejoice because this is going to come back to haunt you. Here's why:

Our dorms had to share the internet connection from a single router. The IP addresses were sequential, like: XXX.XX.XXX.81 ... 82 ... 83 and so on. If someone got an iPhone or iPod touch, they would assign a random dedicated IP from their wireless routers and it would clash with the real owner's computer. So if whoever was using your IP reenters your wireless reach and turns his device on and assigns it your IP when you're not using it, you get screwed again. Its extremely annoying, specially since there is no way to know who is using it. The MAC address doesn't really help.

So a little fix for everyone using a wireless router:

First make sure that someone else in your surrounding is not using a wireless device with your IP address. The next step would be to create your own range of IP addresses. This can be done in the Airport Utility application in ~/Applications/Utilities.

Under TCP/IP, under Internet enter the IP, SM, Router and DNS addresses that your internet service provider has assigned you. Then under DHCP, create a desired range of IP addresses that start from 192.168.1.1. The DHCP End Address is the number of IP addresses you want for yourself. It can be anything till 255. You can keep it till 10 or 20 or whatever, depending on the number of devices you have and can always change it. Update your router and done.

Now, automatically, your router becomes 192.168.1.1, your computer becomes 192.168.1.2, your iPhone becomes 192.168.1.3, your pet cat's netbook becomes 192.168.1.4 and so on. No one gets to take your IP because its a closed range.

Worked beautifully for me ever since I did this.

Please help us - Comcast can't/won't

5 days ago, my husband Kevin's MacBookPro was hacked. Rogue emails were being sent in batches to his address book - and to his inbox as well. There is no subject and the email when opened is just a link:
space4web . sp . funpic . de/ home . php (spaces added by me)
Then the next day, he got a pop up Another device on the network is using your computer's IP address. followed by a series of numbers beginning with 192.
Get this, emails were sent even though his computer was turned off and unplugged. They are being sent while he is online on his MacBook Pro, too.
We called comcast and after 2 hours, they had him manually change the IPv4 address (which was all zeros) and told him to change his email password. Within one minute of changing, the same pop up announcing another device was using the computer's IP.
We have a wireless system. Two macbook pros, one iMac and two PC desktops. We also use 3 iPod Touches.
We are retired and dedicated to caring for our adult son with significant disabilities. I am so worried about our online banking and our meager stock portfolio.
Please, advise us as to what to do.
Thank you in advance.
Pam
Josh's mom

Joshsmom said:

5 days ago, my husband Kevin's MacBookPro was hacked. Rogue emails were being sent in batches to his address book - and to his inbox as well. There is no subject and the email when opened is just a link:
space4web . sp . funpic . de/ home . php (spaces added by me)
Then the next day, he got a pop up Another device on the network is using your computer's IP address. followed by a series of numbers beginning with 192.
Get this, emails were sent even though his computer was turned off and unplugged. They are being sent while he is online on his MacBook Pro, too.
We called comcast and after 2 hours, they had him manually change the IPv4 address (which was all zeros) and told him to change his email password. Within one minute of changing, the same pop up announcing another device was using the computer's IP.
We have a wireless system. Two macbook pros, one iMac and two PC desktops. We also use 3 iPod Touches.
We are retired and dedicated to caring for our adult son with significant disabilities. I am so worried about our online banking and our meager stock portfolio.
Please, advise us as to what to do.
Thank you in advance.
Pam
Josh's mom

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Just a few questions to start:
Are you sure his Macbook Pro was hacked?
Is the mail account a 'webmail' account too? ie. is it like a yahoo/gmail type account? I'm asking because if its his webmail account that's been hacked then I don't think the Macbook's security has been compromised.

With quite a few devices in your household, I do think you will need all your security checked. Not trying to be funny, but are you tech savvy enough to do this? You will need to check all your Windows PCs are up to scratch with antivirus and anti-spyware etc and get the hard drives scanned. Also enabling the firewall on all your computers (both Windows and Apple) is recommended.

The IP issue is another story. You will need to check for:
Type of wireless encryption is enabled, where WPA/2 is recommended. WEP is way too weak and easily hacked;
How many IP addresses are available for distribution by the DHCP compared to how many wireless devices you have;
Make a note of the IP addresses that are giving you problems. eg 192.168.0.1 or whatever and have a look in your router to see which device is already using the IP.

Have you introduced any new devices into your household that may have caused this by any chance?

I could go on but I think you need to take things in smaller chunks.

Edit: If you have a friend or relative who knows what they're doing and can help, it could save a helluva alot of time.

Yes, the email is web based. Well, since I was unable to comprehend the rest of your response, I think this is far too out of our comfort zone. We will contact a local and reputable Data Medics to come and bail us out of this one. Thank you for replying to our plea for help.