No Shutdown Command

Mr Big

Can someone give me a basic summary of the no shutdown command? I know what it does and means, but what happens when you don't assign an IP to the interface, what will that interface do if you just type "No Shutdown". Will it listen to all IP's on that interface?

mgodinez

if you do not assign ips to the interface then it is already shutdown.

administering the 'no shut' command is the last command when configuring ips on a 'fresh' interface.

the interface will appear administratively down to the router and will remain in a blocking state until activated.

regards,

mgodinez
seattle, wa

forbesl

mgodinez wrote:

if you do not assign ips to the interface then it is already shutdown.

Not so. You do not have to assign an IP address on an interface in order to activate it. The "shut/no shut" commands simply turn the interface on or off.

There are certain configurations, for instance bridge irb, where you do not assign an IP address to the interface, you merely turn the interface on and assign a bridge group to it. This is also the case with certain ATM interface configurations where you turn on the interface (no ip assigned to the interface itself), and assign the IP address to a sub-interface.

So, in answer to your question, Mr. Big....if you issue the "no shutdown" command, it turns the interface on and allows any traffic to pass (unless of course you have access-list filters applied).

hectorjhrdz

.........don't go far away.

when you're setting up a trunk on a router interface you don't have to set ip address in it, actually if you set the ip add the trunk will have problems. All this stuff in the physical interface, in sub-interfaces you have to set it.


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