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Community Member

where would a logical vlan be configured on the Core switch, or access switch.

Configuring local Vlans



I have learned to configure the vlan interfaces on the core switch-  and then configure the access switch with the desired vlan and assign the switch port to that vlan!

If I use this design and then allow only (1) one vlan per floor.  would this be considered local vlans?


 - Or do I have to configure a different vlan interface on each access switch found on each floor with one vlan?  



Cisco Employee

Hi,A local VLAN is defined on


A local VLAN is defined on the local switch, not on the VTP server. A local VLAN does not span the entire network, rather it spans a small LAN, each switch seperately configured for VLANs. Therefore there is not a large broadcast domain spanning the network. A local VLAN + layer 3 routing could be used instead of a single layer 2 broadcast domain , or end to end VLAN.

Some more info:

Local VLANs are based on geographic locations by demarcation at a hierarchical boundary (core, distribution, access). Therefore, a local VLAN would never span from an access layer to a core block. Because VLANs are created based on geographic or physical boundaries, it's not uncommon to see much of the traffic leaving the broadcast domain to access a resource. There are two generic rules when dealing with traffic flow: 80/20 and 20/80. The 80/20 rule assumes that 80% of the traffic stays local to a VLAN and 20% leaves a VLAN through a Layer 3 device. Local VLANs assume this premise. Note that with this implementation, VLANs are solely used to solve broadcast problems. With the 20/80 rule, 20% of the traffic stays within the VLAN and 80% leaves it. In this situation, a burden is placed on the Layer 3 device that is used to interconnect VLANs. Although they do introduce a latency issue because of the access of resources outside of the VLAN.





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Community Member

Thank you this does clear up

Thank you this does clear up a few things ..

do you need intervlan routing

do you need intervlan routing and intervlan connectivity ? if yes so you need vlans on core L3 switch.

if no so make separate vlans on every floor on each access switch


and dont forget to rate post

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