ip is a utility for managing network configuration.
ip link show <device> shows the link status for a device.
Manage network devices.
ip link {show | add | del | set} dev IFNAME ... manipulate devices, tab-completion is handy
ip link set dev eth0 {up | down} bring an interface up down
Work with IP addreses.
ip addr {add | del} IFADDR dev IFNAME manipulate addreses
ip
Manipulate the host routing table.
ip route gives routing info.
ip route {add | del} ROUTE to manipulate routes.