Connecting the Ethernet shield

Hi, when I hook up my ethernet shield to my router at home and it is working perfect.

However when I try to hook it up at a local office (wall RJ45 socket), I can't seems to connect. When I connect my PC to the wall socket, I get internet access on my PC...

What are the parameters that I should check and change? e.g. IP address, MAC address?

The IT personnel at the premise could not offer me any help, hence I have to try it on my own....

Don't use a fixed IP address, but use DHCP.

Thanks, it worked.