Something weird is going on with routing from AT&T's 4G network to a subnet of Comcast IP addresses that my home cable modem receives.
Long story short....I have a service called Subsonic running at home that streams my music collection to any browser or to an Android/iPhone app. It's accessible from the internet and has always worked over AT&T 4G...until yesterday.
I did a bunch of troubleshooting trying to eliminate my Galaxy S3 from the equation. Everything else network-related on the phone works fine over AT&T 4G.
The server is up and available when I connect over wifi on my work internet connection and on my friend's home FIOS. My neighbor's GS3 could connect over Verizon's mobile network. However, another friend who lives 15 miles from here could not access it on his AT&T iPhone over 4G, but it worked via his Comcast wifi.
I even pulled another IP for my Comcast modem from DHCP (they were both in the 71.224.x.x subnet), and I still couldn't connect to it over AT&T 4G.
I did a traceroute from my phone on AT&T 4G to my home IP, and it hangs on the second hop (172.26.96.9, which I'm assuming is AT&T's equipment..it's in the same subnet as my phone's IP/gateway) for about 30 seconds before completing the traceroute through to my home IP.
Strangely enough, my Dad lives in the midwest and his phone connects normally over AT&T 4G. It would seem the problem is with routing on the 4G network here on the east coast.
I don't know if it's some "peering dispute" like what was going on with Cogent & Verizon a few months ago or a messed up AT&T router somewhere...but I spent almost two hours on the phone trying to figure it out with AT&T support yesterday, and at the end of my call they were still asking me if I was trying to tether a laptop to my phone.
This is a tough question, I don't have any information on that, but you could look into an alternative music service, like Google Music which is also free. I use it everyday and have no issues. As far as your existing issues, since it just started recently, I would give it few days and see if it gets resolved (AT&T might be performing some maintenance work or upgrades in your area).
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