DNS woes?

Mr. Buttons

I've got this great problem where I can't access around 30% of the webpages I would typically be able to connect to. I've tried everything I can think of, and it's fixed some, but not all of the problem.

I'm running a 2006 macbook with 10.6.7 (updated from 10.6.6 after the problem had started), problem exists in both ethernet and wireless connection. I "cannot connect to server" on several pages, some of which I have gone to on a regular basis, others of which I have never gone to before the problem started. I was having problems with loading images on some pages that would come up (Facebook wouldn't load profile/group avatar pictures, but the site would load up)

The problem exists between browsers, Chrome and safari, but the problem is slightly different between them... In Chrome I can't load cracked.com, I have to load www.cracked.com, but in Safari cracked.com redirects (?) and pulls up the www.cracked.com automatically. But for most pages if it won't load in Chrome, it won't load in Safari (or Firefox) - Just get a "Cannot Connect" message

All my updates are in, Chrome is up to date, Safari too. The problem *only* exists on my macbook, exists regardless of the network I'm attached to (home or school, wired or wireless), and only has affected my computer (wife's computer doesn't have this problem)

I've tried changing my DNS servers with limited success. Using OpenDNS public servers I'm able to load the portions of most pages that weren't fully loading before (example: facebook now loads all images), but the problem wasn't improved when I tried using the google dns. I've flushed my cache (dscacheutil), kill/restarted mDNSResponder, checked my host-file (everything clear). I've also checked my proxy settings (going through network settings), nothing shows up on the list... not sure if it could be hidden anywhere else.

Anyone have any suggestions?

Spudge

Have you checked your hosts file for discrepancies?

The hosts file can be edited to block certain hostnames (like ad-serving/malicious hosts), or used for web development purposes, i.e. to redirect domains to local addresses.

Editing the hosts file

Editing the hosts file in Mac OS X – Leopard, is a pretty easy task, especially if you are familiar with the terminal.

Step 1 – Open the Terminal.app

Either by start typing Terminal on the Spotlight, or by going into Applications -> Utilities -> Terminal.

Step 2 – Open the hosts file

Open the hosts by typing on the Terminal that you have just opened:

$ sudo nano /private/etc/hosts

Type your user password when prompted.

Step 3 – Edit the hosts file

The hosts file contains some comments (lines starting with the # symbol), as well as some default hostname mappings (e.g. 127.0.0.1 – localhost).
Simply append your new mappings underneath the default ones. Or edit one of the default values if you know what you are doing!
You can navigate the file using the arrow keys.

Step 4 – Save the hosts file

When done editing the hosts file, press control-o to save the file.
Press enter on the filename prompt, and control-x to exit the editor.

Step 5 – Flush the DNS cache

On Leopard you can issue a simple Terminal command to flush the DNS cache, and have your host file changes to take immediate effect:

$ dscacheutil -flushcache

Djeet

Can't help you with safari, but in Chrome try disabling "DNS pre-fetch" which seems to break DNS resolution more often than not.

Mr. Buttons

I've checked the hosts file, only localhost (127.0.0.1, ::1) and broadcasthost (255.255.255.255).
I've also disabled the DNS pre-fetch on chrome with no success...

The pages it loads/don't-loads is consistent, it's always the same pages that will load, and the same that won't...

Mugaaz

Can you connect to those pages by IP?

Mr. Buttons

Just tried going by IP.... turns out that's a no too... guess it's not just DNS

Mugaaz

If you have a lot of latency from downloads or something you may just be timing out. Run a trace route towards the IP, see where it fails, contact your ISP.

mcp

Mugaaz wrote: »

If you have a lot of latency from downloads or something you may just be timing out. Run a trace route towards the IP, see where it fails, contact your ISP.

It's happening regardless of the network you're on right?

Something's borked on his machine.

Might be a long shot but, have you tried a file system check, or run Diskwarrior or anything?

Mr. Buttons

Got it working, and it was something borked on my machine..... not sure what exactly was going wrong, but Peer Guardian was a little overactive and was shutting the door on a lot of stuff it didn't need to... a quick uninstall and everything is back to normal (it's been on this system for over 3 months, hadn't caused a problem prior to 2 days ago)

Thanks for all your help!