Implementing Best Practices for LVLAN Topologies

Describing Issues in a Poorly Designed network

Poorly design

Scalable Network Addressing

Interonnection Technologies

Oversubscription

Access to distribution layer links: The oversubscription ratio should be no higher than 20:1. That is, the link can be 1/20 of the total bandwidth available cumulatively to all end devices using that link.
Distribution to core links: The oversubscription ratio should be no higher than 4:1.
Between core devices: There should be little to no oversubscription planning. That is, the links between core devices should be able to carry traffic at the speed represented by the aggregate number bandwidth of all the distribution uplinks into the core.

Traffic types

End-to-End VLANs

Local VLANs a genneraly confined to a wiring closet

Local VLANs should be created with physical boundaries rather than the job functions of the users on the end devices.
Traffic from a local VLAN is routed to reach destinations on other networks.
A single VLAN does not extend beyond the Building Distribution submodule.

Mapping VLANs

When mapping VLANs onto the new hierarchical network design, keep these parameters in mind.

Examine the subnetting scheme that has been applied to the network and associate a VLAN to each subnet.
Configure routing between VLANs at the distribution layer using multilayer switches.
Make end-user VLANs and subnets local to a specific switch block.
Ideally, limit a VLAN to one access switch or switch stack. However, it may be necessary to extend a VLAN across multiple access switches within a switch block to support a capability such as wireless mobility.