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Lessons · Network switches · shut and no shut

A port that is administratively down

`shutdown` disables a port until somebody types `no shutdown`, and until then it will not pass traffic whatever is plugged into it.

Hone is a place to practise programming. This is one of its lessons, written out in full and free to read without an account.

What it is for

Unused ports should be shut, and a port somebody shut during maintenance and forgot is a fault that no amount of cable testing will find.

How to think about it

When a port is dead, read its status first. 'disabled' means somebody did that on purpose; 'notconnect' means nothing is plugged in. They are different problems.

Worked example

enable
The # prompt.
configure terminal
Into configuration mode.
interface gi0/8
A port nobody is using.
shutdown
Off. It will now show as disabled rather than notconnect.
end
Out.
show interfaces status
Gi0/8 disabled. That word means a person did this, not a cable.
configure terminal
Back in to undo it.
interface gi0/8
The same port.
no shutdown
On again. `no` in front of a command is how everything on IOS is undone.
end
Out.

Your turn

Bring a shut port back up.

 shutdown

The trap

Looking for an 'enable' command for a port. There is not one: the opposite of shutdown is `no shutdown`, and that pattern holds across the whole operating system.

Practise shut and no shut on HoneA question on it now, a coding challenge where there is one, and it is remembered for review. Free, no email needed.