Virtual Local Area Networks (VLANs) are an often-misunderstood concept. This section defines VLANs and addresses configurations that require the Avaya IP telephone to connect to an Ethernet switch port that is configured for multiple VLANs. The IP telephone is on one VLAN, and a personal computer that is connected to the telephone is on a separate VLAN. Two sets of configurations are given: Cisco CatOS, and Cisco IOS.