Reason for not being able to telnet to interface Vlan until vlan is created

[jared.j01]

Hello,

I am currently studying CCNA.

During one of my Labs, I created a Interface Vlan 99 but was unsure why it was "status down" and "protocol down" and I could not telnet to it until I created the vlan 99.

I now believe that an Vlan Interface is not accessable until the Vlan it refers to is created.

Is this correct?

If this is the Management Vlan, why does the Vlan have to be created before I can Telnet to it even though I will not be assigning any ports into this Vlan?

Thank you very much for your replies

[Steve Fuller · Accepted solution]

Hi Jared,

It's pretty old, but take a read of the Understanding and Troubleshooting the Autostate Feature in Catalyst Switches document.

The basic idea is that if there are no ports in the VLAN, or the VLAN doesn't exist, the router would black-hole any traffic destined to addresses in the subnet assigned to the SVI. By making the SVI operationally down, the router will stop advertising the prefix assigned to the SVI and so traffic would be forwarded on some alternate path and so be able to reach the destination.

Regards

[jared.j01]

Thank you very much for your reply and explanation.

Sent from Cisco Technical Support iPhone App

[Steve Fuller]

No problem. Good luck with your studies.

Regards

Sent from Cisco Technical Support Android App

[acampbell]

Steve,

Its a +5 from me

Your reference may be older ( so am I) but the basic priciples are well

described

Regards,
Alex.
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