Network unreachable with Ubuntu in DE1-SoC even when the Ethernet cable is connected

I am using Altera DE1-SoC for booting Ubuntu and I am able to boot it and root into it. But when I try to do apt-get update or apt-get install function-name, I am not able to connect to network and it's unreachable always, even when I try to connect through Ethernet. I'm not sure whether my Ethernet cable is getting recognized, but I could see a orange light coming on the port.

This is the error that I get, when I try to connect to the network. I am helpless in this issue and any inputs will be greatly appreciated.

Cannot initiate the connection to ports.ubuntu.com:80 (91.189.88.151). - connect (101: Network is unreachable)

Thanks,

Swaminath