Lucent Technologies P550 - Manual (Page 29)

Cajun P550 Switch Overview
Cajun P550/P220 Switch Operation Guide 1-9
❒ Optional per-VLAN spanning tree - This isolates loop control to smaller domains, so
spanning trees converge faster after a topology change. Otherwise, packets are
forwarded to the port’s default VLAN.
VLAN Functions
A VLAN (Virtual LAN) is a logical group of hosts on a local area network (LAN) that
communicate as if they were on the same wire, even though they are physically on
different LAN segments throughout a site.
Virtual LANs provide network managers with two significant capabilities:
❒ The ability to segment traffic in a flat switched network. This helps prevent traffic
from being forwarded to stations where it is not needed.
❒ The ability to ignore physical switch locations when creating workgroups. VLANs
are logical constructions and can traverse physical switch boundaries.
The switch hardware supports Layer 1, Layer 2, and Layer 3 VLANs. The switch-based
VLANs have the following characteristics:
❒ Frames classified as they enter the switch using Layer 1 (Port-based).
❒ Explicitly-tagged VLAN packets are forwarded based on the information in the
packet.
❒ VLANs define a set of ports in a flooding domain. Packets that need to be flooded
are sent only to ports participating in that VLAN (Figure 1-5).