Extreme Networks ExtremeWare XOS Guide Manual page 224

Virtual LANs
Another benefit of tagged VLANs is the ability to have a port be a member of multiple VLANs. This is
particularly useful if you have a device (such as a server) that must belong to multiple VLANs. The
device must have a Network Interface Card (NIC) that supports IEEE 802.1Q tagging.
A single port can be a member of only one port-based VLAN. All additional VLAN membership for the
port must be accompanied by tags.
Assigning a VLAN Tag
Each VLAN may be assigned an 802.1Q VLAN tag. As ports are added to a VLAN with an 802.1Q tag
defined, you decide whether each port will use tagging for that VLAN. The default mode of the switch
is to have all ports assigned to the VLAN named default with an 802.1Q VLAN tag (VLANid) of 1
assigned.
Not all ports in the VLAN must be tagged. As traffic from a port is forwarded out of the switch, the
switch determines (in real time) if each destination port should use tagged or untagged packet formats
for that VLAN. The switch adds and strips tags, as required, by the port configuration for that VLAN.
NOTE
Packets arriving tagged with a VLANid that is not configured on a port will be discarded.
Figure 8 illustrates the physical view of a network that uses tagged and untagged traffic.
Figure 8: Physical diagram of tagged and untagged traffic
Figure 9 is a logical diagram of the same network.
224
= Marketing
M
= Sales
S
= Tagged port
Marketing & Sales
802.1Q
Tagged server
System 1
M M
M M
S S
S S
System 2
S S
S S
M M
M M
S S
S S
EX_064
ExtremeWare XOS 11.3 Concepts Guide