Mac OSX + Philips router. Not best friends.

October 16, 2010

I ran into some problems lately with my network. Whenever i was browsing the web, my Firefox would just not load some pages, mostly pages that i visited quite often (Wikipedia, Apple Trailers, …). I tried Safari because i thought the problem was one of the add-ons or plugins in Firefox, but Safari also failed. Could this be a problem with my operating system (Mac OSX 10.5) ? I tried bridged networking from a Ubuntu virtual machine. Seemed to work. Other computers on the network had no problems (all windooz and GNU/Linux machines).

After countless hours of searching on google, changing network cables, restarting router and switches over the past weeks, i desperately went to the #macosx channel on the freenode irc network. Users ‘frogor’ and ‘CPng|N’ both suggested that the problem could really be due to the router.

So i fired up the admin panel of my Philips router(model number SNA6500/18). I saw in the logs that the local ip of my computer was sending a lot of unanswered ‘SYN’ traffic to the ip’s of the websites that didn’t work. Google told me that this is normal, the tcp/ip stack of osx uses an option flag that causes this. Anyway, this ‘SYN Flood’ required a lot of tcp sessions and my router limited (and aborted) them, so the connections just timed out.

Long story short, on the router admin panel: Advanced Settings > Firewall > Intrusion Detection > Maximum Incomplete TCP/UDP sessions per host
change that value from 10 to 50 and you’re done.



3 Responses to “Mac OSX + Philips router. Not best friends.”

  1. I have had the same issue in the past. In my case Google Images search result couldn’t display the thumbnails (same happened with other search engines).
    Same solution solved my problem.

  2. Beatrice Says:

    Same here. Thank U so much. A huge problem just solved. Thanks again.

  3. Brian Dueck Says:

    Brilliant! Solved a real mystery for me.

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