curious IOS question

I'm sitting here messing around with a 3550 switch...

Why does the IOS allow you to "attempt" to assign an IP address and mask to a switchport interface and then gives the message:

"IP addresses may not be configured on L2 links"

which I understand but why would the IOS even allow me to get that far? Why is it even an option?

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Comments

networker050184

You want it to know what you are going to type before you do it and stop you?

pamccabe

networker050184 wrote: »

You want it to know what you are going to type before you do it and stop you?

lol the switch has become self-aware!

I don't know the exact answer, but maybe it has something to do with the 3550 being a layer 3 switch. So the hardware does, or can, make switching decisions based on IP addressing. Just a guess, I have no idea.

djlomba

lol.. that would be cool.

But no, I'm curious if it is there for a reason I have yet to learn about.

I'm going to check to see if my 2950 does the same.

pamccabe

networker050184 wrote: »

You want it to know what you are going to type before you do it and stop you?

That would make this CCENT exam I have coming up a whole lot easier too. Not to mention configuring routers/switches in an enterprise environment. A little heads up from the hardware would increase up-time I bet.

networker050184

Some vendor software prevents you from typing invalid commands. At this point Cisco probably doesn't change due to familiarity and no point in trying to implement a new feature that no one really cares about.

powmia

It's because it's a valid command. if you had a layer-3 version of the 3550 with ipservices software, you could issue "no switchport" under the interface... which makes it a routed port... which can be configured with an IP address. The switch lets you type it, and after you do... it realizes you haven't met all of the prerequisites for that command to work.

terryfera

powmia wrote: »

It's because it's a valid command. if you had a layer-3 version of the 3550 with ipservices software, you could issue "no switchport" under the interface... which makes it a routed port... which can be configured with an IP address. The switch lets you type it, and after you do... it realizes you haven't met all of the prerequisites for that command to work.

Came to say this. Once you move on to CCNP you'll see that the multilayer switches can act have routing and routed interfaces available which accept the ip address command. Also keep in mind that when you're configuring VLAN "interfaces" they accept the ip address command as well.

d6bmg

What are you trying to do to be exact?