Fix Mac OS X DNS Failure on UPC Router
About a week ago, I upgraded my MacBook Pro to OS X 10.6.4. Since then, I’ve had trouble with the internet connection *only* from my house and *only* on my MBP. Sometimes the connection would work fine, but most of the time Firefox/Safari would only load the first couple of pages and then new pages would start to time out.
Since I could ping/view a site by going to the server’s IP address directly, the issue appeared to be with the MBP resolving DNS. DNS is how your computer translates a human readable URL such as andyregan.net to a machine readable IP address.
Since the problem was *only* with my UPC connection (router is Cisco EPC2425), I thought changing DNS provider to Google or OpenDNS might do the trick. Alas, the new DNS servers would work for the first few pages and then pages started timing out again.
After poking around the (extremely limited) options on the UPC router, I noticed that there were a ton of firewall blocks for the 192.168.1.0/24 network over the last week. Devices connecting to the router, such as my MBP, are assigned IP addresses within this range.
On closer inspection, I discovered that the router’s firewall was blocking the MBP from the DNS servers for “LAN-side UDP Flood”. I turned off the router’s firewall and restarted it. Et voila! Bob’s your uncle.
My guess is that the firewall blocks must be due to some change in DNS behavior since the last OS X update. Posting here to save some poor soul the heartache. It’s important to note that turning off your router’s firewall is at your own risk.
Hi Andy,
Christ at last someone with the same problem as me. Ever since I changed to UPC a couple of months ago I’ve had this shit going on every time I try to go online. i want to get this sorted and I would be willing to try turning off the firewall on my router but don’t know how to do it. Could you give me some advice on how to do it?
Thanks
Hi Declan,
Sorry for the delay in getting back. Try going to http://192.168.1.1/ in your browser. Leave both login fields blank and hit ok. On the “setup” tab, under “firewall:”, click on “options”. From there, you can disable firewall features. I have disabled all features and am using a separate firewall.
Andy, than you so much for this great tip. I live in Poland and UPC is my Internet provider. Recently they’ve upgraded my modem to the “latest and greatest” Thomson TWG870U and I’ve had nothing but problems ever since (the same exact symptoms you described).
As soon as I have switched off IP Flood Protection all of my problems have gone away
This was happening me but bizarrely the firewall was off. My solution was to set the Cisco modem to Bridge mode and use another router instead. Now working like a charm.
Thank you so much Andy!
This was exactly my problem with a Thomson TWG870U.
In my case the admin page was at http://192.168.0.1 and username blank pwd “admin” worked!
Thanks man!
You’re welcome!
Andy, by this post, you have solved a problem that I had been battling with for a couple of fraught days.
Please accept my thanks.