GS748T Software User Manual
Configuring the Switch 4-7
v2.0, April 2007
VLAN Page A Virtual Local Area Network (VLAN) is a means of electronically separating ports on the same
switch from a single broadcast domain into separate broadcast domains. By using VLANs, users
can group nodes by logical function instead of physical location. For example, Engineering and
Accounting department traffic can be separated from one another. VLAN memberships are
manipulated by associating switch ports with VLAN IDs (VIDs).
You can choose from two types of VLAN to set up on the switch: IEEE 802.1Q VLAN (Tagged
VLAN), or Port-based VLAN. You cannot mix the types on the same switch. In either case, any
port can be a member of multiple VLANs.
• IEEE 802.1Q VLAN: The VLAN tagging option is a standard set by the IEEE to facilitate the
spanning of VLANs across multiple switches (Reference: Appendix A and IEEE Std 802.1Q-
1998 Virtual Bridged Local Area Networks). This switch supports the creation of 64 Static-
Tag VLAN groups.
This implementation separates traffic by adding a VLAN tag into the appropriate egress
frames (packets) from selected switch ports. A receiving switch associates the tagged frame
with the VLAN and forwards it, according to its own VLAN-to-port lookup table, to all ports
on the VLAN except the ingress port. In this way, a VLAN structure may be built across a
“tree” of switches.
You have the option of setting egress frames to be:
• Tagged: this setting adds an 802.1Q tag into the frame leaving the selected port
• Untagged: this option strips the 802.1Q tags from frame leaving the selected port. The port
retains its association with the VLAN. This facility is used when these ports are connected
to downstream equipment that does not recognize (and which consequently may be
confused by) 802.1Q tags.
• Unchanged: this option is the default and signifies that the port is not associated with a
VLAN.
Every port is a member of VLAN ID 1 by default. You can change the default assignment of
any port adjusting the Primary VLAN ID Setting (PVID) table. Use this feature to ensure that
untagged frames reach the VLAN that you require.
• Port-based VLAN: This implementation confines VLAN members to the ports on the
particular switch, that is, the VLANs cannot span multiple switches. VLAN membership of
ports is determined in a lookup table that you set up when you configure the switch. You can
create up to 48 port-based VLANS. Every port belongs to VLAN ID 1 by default.