Internet Connection Sharing

What I am attempting to do should be a fairly simple task, but I just can’t seem to come right.

I am trying to share a single Internet connection with all the computers in the office.

My network is layed out as follows:
Telephone line > ADSL Modem > Mikrotik 750G > LAN Switch > Office Computers.

I have set up a PPPoE connection on the 750G, and I can ping from it through WinBOX. But when setting an office computer to use the 750G as the default gateway, I can’t connect to the internet or even ping from that PC.

I have also set the PPPoE connection to add the default route and the firewall is setup to masquerade.

What am I doing wrong? Everything else on the router is left as default.

you probably need a masquerade rule in the router, if your LAN is using private addresses and that’s your preferred method.

http://wiki.mikrotik.com/wiki/Manual:IP/Firewall/NAT#Source_NAT