Network connection broken by TimeMachine?

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Network connection broken by TimeMachine?

It sounds strange I know this but I can reproduce the following problem:

I have connected my iMac (Mac OS X Mavericks) with WiFi to an 802.11a/n AccessPoint with 270/300Mbit/s.

The whole time I see trafic on the Interface en1 (wireshark).

If I start a Time Machine Backup (manually or by backupd) it comes to the point that I cannot use my Wifi anymore. This is not a speed problem and no connection problem(!), because I can SEE incoming traffic from my network but can't reach anything outside my iMac: ping localhost or ping <ip of interface en1> works, but ping <IP of default gateway> doesn't.

After I disable the Airport and re-enable I can work without problems and the already started Time Machine backup goes on. Crazy, isn't it?!

iMac, OS X Mavericks (10.9)

Posted on Nov 12, 2013 7:21 AM

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Answer 1

etresoft

Level 8

46,236 points

Nov 13, 2013 5:20 AM in response to sputniki

Is there a firmware update for your router?

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Answer 2

sputniki Author

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Nov 15, 2013 5:38 AM in response to etresoft

It is not a problem of the wifi-AP. If I disable my local time machine backup I don't have this problem.

AND I do not have connection problems: I can see incoming traffic from the AP but no packet is leaving my wireless card from my iMac (airport card). It looks like time machine touches some files in filesystem and after that's no IP communikation from layer2 to the MacOS is possible. (I can see ARP-request for IP address going and the answer coming in with wireshark)

In addition there are four other iMacs connected with the access point, having no problems.

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Answer 3

etresoft

Level 8

46,236 points

Nov 15, 2013 7:12 AM in response to sputniki

What modifications have you made to this machine?

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Answer 4

sputniki Author

Level 1

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Nov 19, 2013 4:31 AM in response to etresoft

At first I created a new network profile for connecting to the wifi AP.

Then I connected my iMac with ethernet connection to re-enable time machine backup (it works via ethernet).

What else? Uhh I used the Apple Wifi Diagnostics but could not see more then the co-occurrence of starting time machine backup and connection loss with wifi.

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