About changing an interface status up or down

Sometimes you have to make an interface inactive before you can perform certain tasks and then make it active again after you complete a task. You do this by entering an up or down parameter in the ifconfig interface command.

You need to change the interface status before you:

If you have disabled IPv6, you can change the status of a network interface only after configuring the interface with an IPv4 address. If you have enabled IPv6, you can bring up the interface without a valid address configured because a link-local address is created automatically for the interface. However, if the /etc/rc file contains an entry to keep a network interface in down status, a link-local address is not created.

• Changing the up or down status with ifconfig
  To change the status of an interface, you use the command-line interface and the ifconfig command.