VLANs are used to break large campus networks into smaller pieces. The benefit of this is to minimize the amount of broadcast traffic on a logical segment.
A virtual LAN (VLAN) is a logical LAN, or a logical subnet. It defines a broadcast domain. A physical subnet is a group of devices that shares the same physical wire. A logical subnet is a group of switch ports assigned to the same VLAN, regardless of their physical location in a switched network. VLAN membership can be assigned either statically by port, or dynamically by MAC address or username.
Two types of VLANs Are:
■ End‐to‐end VLAN: VLAN members reside on different switches throughout the network. They are used when hosts are assigned to VLANs for policy reasons, rather than physical location. This provides users a consistent policy and access to resources regardless of their location. It also makes troubleshooting more complex because so many switches can carry traffic for a specific VLAN, and broadcasts can traverse many switches
■ Local VLAN: Hosts are assigned to VLANs based on their location, such as a floor in a building. This design is more scalable and easier to troubleshoot because the traffic flow is more deterministic. It enables more redundancy and minimizes failure domains. It does require a routing function to share resources between VLANs.
Create and Delete a VLAN
VLANs must be created before they can be used. Creating VLANs is easy— in global configuration mode just identify the VLAN number and optionally name it!
(config)# vlan 12
(config‐vlan)# name MYVLAN
Delete a VLAN by using the same command with no in front of it. There is no need to include the name when deleting.