Technical data

BMD00136, November 2009 47
CHAPTER 3
VLANs
This chapter describes network design and topology considerations for using Virtual Local Area
Networks (VLANs). VLANs commonly are used to split up groups of network users into
manageable broadcast domains, to create logical segmentation of workgroups, and to enforce
security policies among logical segments. The following topics are discussed in this chapter:
 “VLANs and Port VLAN ID Numbers” on page 48
 “VLAN Tagging” on page 50
 “VLAN Topologies and Design Considerations” on page 54
This section discusses how you can connect users and segments to a host that supports many
logical segments or subnets by using the flexibility of the multiple VLAN system.
 “Protocol-Based VLANs” on page 58
 “Private VLANs” on page 61
Note – VLANs can be configured from the Command Line Interface (see “VLAN Configuration”
as well as “Port Configuration” in the Command Reference).
Overview
Setting up virtual LANs (VLANs) is a way to segment networks to increase network flexibility
without changing the physical network topology. With network segmentation, each switch port
connects to a segment that is a single broadcast domain. When a switch port is configured to be a
member of a VLAN, it is added to a group of ports (workgroup) that belong to one broadcast
domain.
Ports are grouped into broadcast domains by assigning them to the same VLAN. Frames received in
one VLAN can only be forwarded within that VLAN, and multicast, broadcast, and unknown
unicast frames are flooded only to ports in the same VLAN. The G8000 supports jumbo frames up
to 9,216 bytes.