Two methods can be used to bring interfaces up or down.

From the command line, use:

  ip link set dev <interface> up
  ip link set dev <interface> down
  
  Example:
  ip link set dev eth0 up
  ip link set dev eth0 down

From the command line, use:

  /sbin/ifconfig <interface> up
  /sbin/ifconfig <interface> down
  
  Example:
  /sbin/ifconfig eth0 up
  /sbin/ifconfig eth0 down