VLAN on layer 3 switch - question

[nuggetinu]

I am finding it difficult understanding this term found in a book and considered as a drawback for Layer 3 switches in the access layer - Implementing Cisco IP Switched Networks (SWITCH) Foundation Learning Guide.

"A VLAN on one Layer 3 access device cannot be on another access layer switch
in a different part of your network because each VLAN is globally significant."

Can someone elaborate the significance of this term and why is it considered as drawback in terms of Layer 3 in the access layer?

Thanks in advance,

[Reza Sharifi]

The reason for that is because if you run layer-3 at the access layer, that limits you from spanning vlans across different closets/floors. For example, say you have a builfing with 3 floors and you want to run the same vlan for all floors, that will only work if the access layer switch is layer-2 and the routing takes place on the distro or core. But if the access switch is layer-3, you can only run one vlan for each closet/floor, so you are forced to have 3 vlan/subent for 3 floors versus one vlan for all closets/floors.

HTH