Netwok Connection is lost

I am new to VMware.

I have ESXI 5 Hypervisor installed on server. By vSphere Client I changed the speed of vmnic0 from auto (100) to 1000. I have lost network connections. Also configure management network is disabled now in server main splash screen.

Later I returned the vmnic0 to auto parameter with esxcli command but management network is still disabled, no IP assigned yet