The ip address range
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
is reserved for private network only. You can't have a public ip
address in this range. If you are using LAN, you might be using
10.x.x.x and 172.x.x.x or 192.x.x.x over WiFi your local ip address.
Whatever proxy you are using, is blocking connection to private
network because of its reserved use.
In case of Skype, the application has inbuilt proxy feature which
might not be blocking connection to reserved private network.
--
Sanpreet Singh
http://sanpreetsing100.blogspot.in/