I have a 2013 MBP on 10.10 that I've tested on multiple wireless networks. On all I see this behavior: I get an IP address and DNS servers, but cannot ping mg router or DNS servers (request timeout) or internet IP addresses (no route to host) or URLs (unknown host).
I've tried rebooting in safe mode, as a different user, and in a new 'location'. I don't have access to a wired connection. I don't have any firewall software and my VPN is disabled.
Edit: This issue occurs on five open networks that I've tested. However, there's a password protected network which I can use to get online with. When I get access to a router I can administer I'll see if I can verify this is indeed the cause.