Virtual LAN (VLAN)
- Modern Ethernet networks are built with switches
- by default, every port is in the same local segment (same broadcast domain)
- At the Network layer, this group is an IP Network or subnet within an IP network
- any host in a broadcast domain can contact any other host using:
- the same logical addressing scheme (IP subnet)
- by hardware/MAC address
- if too many hosts are attached to the same switch, broadcast traffic can become excessive and reduce performance
- can address this problem at:
- layer 2, with virtual LANs (VLANs)
- and layer 3 with subnets
A virtual LAN (VLAN) is a logically separate network, created by using switching technology.
- Even though hosts on two VLANs may be physically connected to the same cabling,
- local traffic is isolated to each VLAN so they must use a router to communicate
- each interface on a managed switch can be assigned a VLAN ID
- using VLANs, different groups of computers on the same cabling and attached to the same switch can appear to be in separate LAN segments
- each VLAN is a separate broadcast domain