For an ipad or a mac you typically go to Settings and then network and there are two settings.
 
IP Address should be set to DHCP that configures your ip address automatically.
 
HTTP Proxy can be set to Auto with configuration URL http://10.0.1.50/intranet/proxy.pac or it can be set to Manual using the proxy address 10.0.1.28  port 8080
 
 
Please do not confuse these two settings.