DISCLAIMER: Maybe this isn't the right place for this. Please let me know if it isn't.
I recently stayed at a Hilton Garden Inn (member of the Hilton hotel family). While there, I connected my computer via ethernet to their network (which, as near as I can tell, is run by AT&T). When I did I was surprised to see that I received a public IP address in the 50.95.2.xxx pool with the subnet of 255.255.255.128, and a router of 220.127.116.11
In order to determine if I was publicly accessible, I ran a small server on my laptop and connected from my computer located at home, where Comcast is my ISP (accessed over VNC). I've seen this happen to me a few times before, but not always. It seems to be random. I'm not using the "premium access" which is aimed at business customers with VPNs, just the basic complementary one that is for surfing email or the web.
Connecting using a different thunderbolt->ethernet adapter (thus a different NIC) results in me getting a 192.168.x address, which I see on my other devices (phone, iPad).
Has anyone else seen this / has anyone found why it happens? It seems very insecure to give out public addresses to random hotel clients. Unsuspecting average users might have a configuration where they have something running that (typically behind NAT) isn't a problem, such as guest access to file shares or a vnc server with an insecure password. Not to mention the v4 address shortage.
EDIT: it had all the normal constraints such as a captive portal and 2-3 megabit speed restrictions.