Flexibility and Scalability

Flexibility and Scalability
VLANs also add more flexibility to your network by allowing only the users you want in the
broadcast domain regardless of their physical location. Layer 2 switches read frames only for
filtering; they do not look at the network-layer protocol. This can cause a switch to forward all
broadcasts. However, by creating VLANs, you are essentially creating separate broadcast
domains. Broadcasts sent out from a node in one VLAN will not be forwarded to ports configured
in a different VLAN. By assigning switch ports or users to VLAN groups on a switch—or
a group of connected switches (called a
switch fabric
)—you have the flexibility to add only the
users you want in the broadcast domain regardless of their physical location. This can stop
broadcast storms caused by a faulty network interface card (NIC) or stop an application from
propagating throughout the entire internetwork.
When a VLAN gets too big, you can create more VLANs to keep the broadcasts from consuming
too much bandwidth. The fewer users in a VLAN, the fewer users are affected by broadcasts.