[afnog] VLANs on Cisco Catalyst 2950

[Mark Tinka]

On Friday 26 May 2006 13:46, Bruce Zamaere wrote:
> Guys,
>
> I can't do "switchport trunk encapsulate dot1q" on my switch
>
> "switchport trunk ?" doesn't list encapsulate as an option.

That's funny... are you sure you are in interface configuration 
mode?

> I'm running 12.1(13) IOS on a catalyst 2950 Series.

The Cisco web site feels a little flakey today, so cannot verify 
this for you yet; but I've run both 12.1(22)EA6 and 12.1(22)EA7, 
and both have .1q in the feature set.

But then again mine is a CRYPTO EI image for 2950-T. It would 
help if you could give us your exact 2950 model, as shown at the 
back of the device. Also, advise available flash and memory.

> If I am on the switch through a console cable. I have set up
> ip on each vlan interface why can I ping interfaces on the
> same switch?

Not sure I understand your question - please explain or rephrase.

> I thought this would be ideal for troubleshooting 
> purposes. How does the IOS actually use the VLAN interfaces if
> they are shutdown? I find this a bit confusing to be honest.

It's probably a good idea to remember that your switch is a Layer 
2 device, and for the most part, will be providing services at 
that level.

Any VLAN interface is used mainly to provide some kind of Layer 3 
remote access to the switch for maintenance and configuration 
(things you can do over the console, but may not have physically 
next to the switch to do).

You should not view the VLAN interfaces as an integral part of 
the operation of the switch, which is, for all intents and 
purposes, switch Layer 2 among its ports.

That said, the state of a VLAN interface will not (or should not) 
interfere with the actual operation of that (or any) VLAN. VLANs 
are a Layer 2 function. Accessing the switch over IP is a Layer 
3 function.

> Finally is there a way to trick or to force the IOS to bring
> up more that one VLAN at once?

On the desktop switch you are using, not that I know of.

> I noted 2 or three other people 
> had asked a similar question on posts on the net but the
> question wasn't satifactorily answered. I'm asking this cause
> on some cisco vlan configs I came across the "no shutdown"
> command was issued on the vlan interfaces. Is the problem I am
> facing just a Catalyst 2950 problem???

This brings me back to my question posted earlier; through the 
router, you will be able to access the switch, over IP, from any 
VLAN. This solves your problem. 

Picture this, say you have 1,000 VLANs on your switch/network, 
will you want to create 1,000 VLAN interfaces so each can have 
access to the switch, when one will do the job?

Again, the state of a VLAN interface has little or no bearing on 
the operational capabilities of the actual VLAN (or the hosts 
within that VLAN) itself.

Hope this helps.

Cheers,

Mark.
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