Hi,
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.
HTH
Regards
Inayath
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