Port 4 on 2850 can be used by WAN2 or LAN, and the default is WAN2. To change it to be used by Port 4, all you need to do is to disable WAN2, so Port 4 will be open for LAN.
Change Port 4 to a LAN-Port
1. Set up WAN2. Go to WAN -> General Setup -> select "Index: WAN2”
2. Disable WAN2
select "No” -> press "OK”
3. WAN2 has become grey, which means it has been disabled. Port4 is now open for LAN.
4. To recognize Port4 is being used by LAN or WAN2, go to LAN ->VLAN -> Enable
a. P4 is gray, which means WAN2 is activated.
b. P4 is selectable (black), which means WAN2 is disabled and Port4 is open for LAN.