If you are running Linux, you have several alternatives to put second Ethernet interface for good use.
KVM (Keyboard, Video, Mouse) is a switch or hardware device allows a single keyboard, video monitor and mouse to control more than one server one at a time. KVM can be local device or remote device working over IP network. KVM devices extensively used in server farms where it is only necessary to periodically access box. KVM allows you to access your server even if a remote public network connectivity is down.