Safari 6 Won't Load Certain Web Pages

Hi David, has apple changed the way the use "jumbo frames"? as it works fine in Lion on the same network.

I am using a D-lInk Dir-615 with a DD-WRT (v24 sp2) firmware, this is then connected through a TP-Link 24port ethernet switch(sg1024)

When i changed my MTU to 1300 it's working great and really fast.

i upgraded 3 of my 4 mac's to ML and all work fine when i change the MTU to 1300, my Lion iMac is still using the default settings.

I have no idea. It's just a theory, and here's my logic: I can only think of two aspects of networking (other than the fragmenting process itself) that should be significantly affected by MTU: jumbo frame support and path MTU discovery.

I'd be surprised if path MTU discovery were at fault, because lots of Mountain Lion users go to YouTube regularly, and I don't see everyone screaming about this. So unless your local router is so utterly broken that it always refuses to pass along any packets marked "do not fragment", I wouldn't expect it to be the culprit.

If you want to check to see if path MTU is likely to encounter problematic behavior, though, you might try using ping with the -D flag to set the "Don't fragment" bit. If you get a lot of packets that bounce back (e.g. ping: sendto: Message too long) even with fairly small ping sizes (use the -s flag to set the size), then some part of your route is doing something naughty. :-)

Either way, it's a really bizarre behavior. Jumbo packets seems like a possibility because switches that don't support jumbo frames typically drop them entirely, so a single non-jumbo-frame-capable switch between two fully jumbo-frame-capable devices could potentially cause serious headaches, or at least historically did. Not sure about how that is handled by modern OSes.

I had a similar problem with images not displaying properly after the ML upgrade and was able to trace it to a DNS issue (unrelated to the ML upgrade) by using the Timeline Recording option in the Safari 6 dev tools - very handy. Showed me that certain site names (obscure ones used for facebook images etc...) weren't resolving using root hints (and no forwarders were set). Set some forwarders to Google's public DNS and all is good again. Just thought I'd post this in case someone else is having trouble diagnosing these sorts of issues. That Timeline Recording tool is very handy.

I'm having this problem with only one website - my wordpress blog, which I logged in to, and now the site won't load at all. Not in Safari 6, Firefox, or Chrome. This is after I updated to Mountain Lion.

Other sites like Facebook and YouTube work fine, so it's not all of the log in sites that are affected.

So far I've tried many things in this thread, including wiping my DNS cache, reseting Safari, and even changing the MTU to 1300.

None of them have worked.

I'm using a time capsule as my router, and everything is up to date software-wise, on my computer and time capsule.

Bummer!

I still haven't been able to get it working, even after the 10.8.1 update today.

I tried changing the MTU. Maybe I'm not doing it correctly or something. I just went to the sytem prefs and did manual / custom and changed to 1300 (also tried 1380), then clicked OK, then Update. Is that how you all did it?

Thanks for any help.

What's the URL of your blog? I assume you've tested it from another machine (perhaps outside your network) to confirm it's not a blog issue. The last time I saw this sort of thing, it was because the IP had been blocked because of a suspected port scan on the webserver. Have you checked with your hosting company to see if your IP has been blocked?

Can I ask what is the 'MTU' and under what category of settings would I find it under? There are pages and pages of settings for my router and I don't know where to start!

Change it on your affected mountain lion mac.

Go to system preferences, network, then choose weather you are connected via Ethernet or wifi

Then i think it's advanced (I am doing this from memory as I am not near my mac at the minute)

Then hardware and change the mtu to 1300

Thank you for that - I have found the setting.

Can you explain to a layman why *reducing* the MTU helps in this situation?

Also, I don't get why only Safari would be affected by this system setting when Firefox and Chrome seem fine?

My site is www.madebyjoel.com. It's still not loading with any of the browsers on my computer. Other computers it loads just fine.

Interesting idea on the IP blocking, but I don't think that's it. If I'm on a different internet connection, it still doesn't load. Also, the entire site just moved to a new server yesterday, and it still doesn't load for me. Crazy.

Your site loads fine on my Mountain Lion machine (at least the main page), so the problem is probably something highly specific to your machine's configuration. I assume you've tried creating a new network configuration?

Ah ha! I figured it out, and it's defenitely not Apple's fault.

When my old site designer did my site, it was on his server, and he had me go into my host file to point my website to his server. That server no longer exists, because we just moved the site to a different server. So I just had to go into the terminal and delete my site from the host file. Now it works!!

Sorry Apple! My fault.

Okay, I'm late to this party but my pain is no less for it. A new operating system, Mountain Lion, has been installed on the two iMacs in my home/business and my internet slows to a crawl - on both machines, on ALL three browsers - AND now the AppleTV also downloads at a snail's pace - rendering watching shows and movies all but impossible.

It's pretty clearly a wifi problem. I've done a lot of the stuff I've see posted on various boards. Changed network "Locations" and also deleted and re entered passwords in the keychain. All to no avail. Is there a fix for it? Has anyone REALLY figured out what the problem that SO many of us are experiencing is?

It's more than annoying. It's also biting into Apple's revenue when we can't watch stuff...

Can you help?

Cheers,

Cam R

Changing the MTU to 1300 really helped me. I haven't had an issue since changing it.

Okay, I'm late to this party but my pain is no less for it. A new operating system, Mountain Lion, has been installed on the two iMacs in my home/business and my internet slows to a crawl - on both machines, on ALL three browsers - AND now the AppleTV also downloads at a snail's pace - rendering watching shows and movies all but impossible.

Is the Apple TV slow when viewing local content from the Macs or when streaming video from the Internet?