IP address conflict - pls help...

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Level 1

8 points

IP address conflict - pls help...

Hi

I get on my iMac (and also on the MacBook) sometimes the message: *Another device on the network is using your computer's IP address (10.0.0.8).* After a view seconds (and evidently a change of the IP address) Ethernet connectivity works again. When does this happen: e.g. after waking up the Laptop from sleep modus.

Here is my setup:

. ADSL router with 10.0.0.138 GW address

. all devices directly connected via a Gigabit switch

. most devices are set to DHCP except one

. one device needs to have a manual set IP address (set now to 10.0.0.180), because it does not support DHCP (is a special HW for the solar system)

. devices connected via Ethernet cable include:

- iMac DHCP

- Windows PC DHCP

- Apple Time Capsule DHCP

- PS3 DHCP

- TV Samsung LED DHCP

- SAT Receiver Sky+ DHCP

- NAS DHCP

- Fronius Data Logger static IP 10.0.0.180

. devices connected via WLAN (to Apple Time Capsule) all using DHCP

- Apple TV

- Wii

- iPhone 4

- 2 iPads

- Samsung mobile phone

- MacBook

All have DCHP activated.

I dont understand how a device can get the same IP address from the DHCP and so causing an IP address conflict. Unless, there are 2 active, which I did not yet figure out...

What did I change lately (before this change, I did not have this problem)?

. I had another router behind the ADSL router, set to 192.168.0.x internal address range for the home network. It got broke so I took it out of the setup as the new ADSL router anyway has a firewall. Since then I have these issues.

What does "got broke" mean - as I am not sure whether this helps in finding the root cause: what happened is that after our vacation when I switched on all clients again I could surf the Internet lets say for 1hour or so and then suddenly all clients lost connection and had an 169.254.0.x IP address. And this although DCHP IP address lifetime of the router was set to 24h and the actual lifetime of the clients IP addresses where in that range (as I reseted the router). Before our vacation all was fine. BTW, the ADSL router works fine (I use also IPTV service over it and it works perfectly all the time).

So before that change, I had a private network segment with 192.168.0.x extending from the router to all wireline devices. I am not sure, but it can be that the Time Capsule, i.e. the wireless network, was on 10.0.0.x (I dont know). Then things would be clear to me, as then evidently the Time Capsule runs a separte DHCP from which the wireless devices fetch their IP address and if they are now all in the same network segment (both wireless and wireline)...then "Houston we have a problem":)

So my questions are:

. is the Airport setting of the Time Capsule wrong? I used "create a wireless network". Is it now just extending the 10.0.0.x network to the wireless domain? Hence do the wireless clients fetch their IP addresses from the ADSL router or the Time Capsule?

. Is the wireless and wireline network fully transparent, can wireless devices connect without problems to a wireline device (e.g. the MacBook to the NAS)?

. Is there an app that helps to identify the clients? I can get from my router a list of IP addresses used by clients, but I cannot link them to the devices.

BR

a

Posted on Jul 28, 2011 10:32 AM

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Answer 1

Top-ranking reply

Bob Timmons

Level 10

190,162 points

Jul 28, 2011 2:00 PM in response to Alexollon

Hence do the wireless clients fetch their IP addresses from the ADSL router or the Time Capsule?

This sounds very much like you have two routers (the Time Capsule is a router) that are both configured to provide DHCP services, which will always cause conflicts on a network.

You only want one router handling DHCP on a network and all the other routers should be configured in Bridge Mode to allow proper network operation.

I assume that the Time Capsule is connected to your router using an Ethernet connection. Open AirPort Utility and click Manual Setup for the Time Capsule, then click the Internet icon.

The setting for Connection Sharing should be set to "Off (Bridge Mode)" to allow proper operation of your network. Click Update to save the changes on the Time Capsule.

Then....very important....power down your entire network, all devices, order is not important. Wait a moment then start your modem/router first and let it run for a minute by itself. Start the Time Capsule the same way. Keep starting devices one at a time until everything is powered back up.

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Answer 2

Caledai

Level 1

25 points

Jul 29, 2011 4:25 AM in response to Alexollon

If the TC was not in bridge mode, that was most likely your cause.

A TC in bridge mode, will pass on DHCP/DNS from your router to all wireless devices - it just wont do any firewall/nat tasks.

In bridge mode it can still be used to "Extend a Network" as that feature is independent of the wireles bridging.

Generally speaking, unless you are using a modem that only issues one address (rare these days) - you are better off leaving TC's and Airport Extremes/Expresses in Bridge as most home ADSL Modems are capable of running your network.

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Answer 3

Nov 11, 2012 12:39 PM in response to Alexollon

Same issue described above:

-TM has ip conflict with other device on network

-root cause unclear

Solution:

Open Airport Utility

- Network should be ste to bridge mode

- Internet: Connect using static IP

Open 2Wire control panel and set same static ip for TM

No more conflicts

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Answer 4

wdwmac

Level 1

0 points

Aug 12, 2011 3:34 PM in response to Alexollon

https://discussions.apple.com/thread/3250823

I am having a similar issue as described in another post. search "Time Capsule IP address Conflict". This is a relatively large home network with a number of media devices, PCs and Macs on a network behind and ATT uverse 2wir router.

Everything worked fine until I added the Time Capsule to the network. Initially the TC got an IP address frou the 2wire router and all was fine. But the next day I recieved and IP addres conflict from a Mac Book.

TC is Bridge mode - Wireless turned off - attached diretly to a lan port on the 2wire router.

It looked like the TC recieved an IP address from the 2wire router but the 2wire indicated that it was a static IP, rather than one being issued by DHCP. The 2wire handed out the same address to the Mac Book.

I shut down the TC and the Mac Book, rebooted the TC and Mac Book. Everything seemd to be fine. This time the TC got an address from the 2wire DHCP pool 192.168.1.113. This gave me the opportunity to reserve the address hoping that the TC would get this address every time, and keep it from being handed out to another device.

Everything seemed fine for a day.

Next day we get another address conflict.

The airport utility on an Imac still says that the TC is 192.168.1.113 but the 2wire router does not show the .113 address. Instead it says that the TC has a static IP of .117 .

The Mac Book shows an address of .117.

Shut down the TC

Shut Down the Mac Book

Reboot the Mac Book and Manually assign .120

Change the Macbook to get DHCP address. It now Gets .120 I reserve .120 for the mac Book

Reboot the TC

It gets .113 and shows up on the 2wire router as .113 issued from DHCP.

Reserver .113 for the TC again.

Waiting to see what happens.

Does the TC go to sleep?

If so does it lose its IP assignment and get a new one when it wakes up?

While it's asleep does DHCP try to give its address to another device?

I would be tempted to blame the DHCP service in the 2wire router accept everything works fine when the TC is not on the network.

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Answer 5

Bob Timmons

Level 10

190,162 points

Jul 29, 2011 8:19 AM in response to Alexollon

If the TC is in Bridge Mode, it only passes through the information that it receives from your modem/router.

If you continue to see conflicts on the network, the DHCP server on your modem/router is likely not functioning correctly, and the device will likely need to be replaced.

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Answer 6

Alexollon Author

Level 1

8 points

Aug 15, 2011 2:05 PM in response to wdwmac

I got an network specialist from my provider on site:)

After changing the modem we still encountered the issue both within the wireless and the wireline network part (even with some potential critical network clients switched off). So for the time being it might be an SW issue of the latest modem SW (the time of the SW uograde correlates pretty much with the time my problems started). They will try to verifiy the issue in the lab...

I keep you posted...

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Answer 7

Alexollon Author

Level 1

8 points

Jul 29, 2011 4:18 AM in response to Bob Timmons

hi bob,

thx for the input. I checked the setting, it was correct ("Off (Bridge Mode)"). I just found in the DNS setting an old IP address (192.168.1.1), so I deleted that one. Can that have been the problem?

The powering off and on I have to do yet...

br

a

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Answer 8

Alexollon Author

Level 1

8 points

Aug 6, 2011 2:31 PM in response to Bob Timmons

hi

back from vacation:)

It still does not function correctly. Basically everytime I wake up a computer after longer sleep time there is the window with the conflict. Then after a few seconds (sometimes I have to go to the network settings and refresh) it finds a non-double IP address.

I am not sure whether the modem is the problem - to be honest, I would be surprised. I still have the feeling I am overlooking something. Is there no other way to find out whether I have a second DHCP running that I have not identified yet???

No app can find DHCPs in my network?

br

a

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Answer 9

Mar 30, 2013 1:27 AM in response to Alexollon

I have a similar issue with a MacBook Air when it wakes from sleep. It connects by wifi to an Airport Extreme with that supports dual channel wifi (2.4ghz and 5ghz).

The Airport Extreme is set in Bridge mode. There is also a TimeMachine on the network but its wifi is off. All this is connected to a Dlink game router that is providing the IP addresses.

I was wondering if the dual channel is at issue. That is, the Macbook Air is connected using one wifi and may be trying to connect to the other wifi.

I have a printer that only supports IP addressing so I have assingned it a static IP address.

Should this static IP address be outside the range of IP addresses to be provided by DHCP?

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Answer 10

Alexollon Author

Level 1

8 points

Jul 29, 2011 5:55 AM in response to Caledai

The TC WAS in bridge mode all the time...

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