Interlogix NS2503-24P/2C User Manual - Manual (Page 71)

NS2503-24P/2C User Manual
71
802.1Q VLAN
Tagged-based VLAN is an IEEE 802.1Q specification standard. Therefore, it is possible to create a VLAN across devices from
different switch vendors. IEEE 802.1Q VLAN uses a technique to insert a "tag" into the Ethernet frames. Tag contains a VLAN
Identifier (VID) that indicates the VLAN numbers.
You can create and delete Tag-based VLAN. There are a total of 256 VLAN groups that can be configured. Once 802.1Q VLAN
is enabled, all ports belong to the default VLAN with the default VID defined as 1. The default VLAN can’t be deleted.
Understand nomenclature of the Switch
■ IEEE 802.1Q Tagged and Untagged
Every port on an 802.1Q compliant switch can be configured as tagged or untagged.
 Tagged Ports with tagging enabled will put the VID number, priority and other VLAN information into the
header of all packets that flow into those ports. If a packet has previously been tagged, the port
will not alter the packet, thus keeping the VLAN information intact. The VLAN information in the
tag can then be used by other 802.1Q compliant devices on the network to make
packet-forwarding decisions.
 Untgged Ports with untagging enabled will strip the 802.1Q tag from all packets that flow into those
ports. If the packet doesn't have an 802.1Q VLAN tag, the port will not alter the packet. Thus,
all packets received by and forwarded by an untagging port will have no 802.1Q VLAN
information. (Remember that the PVID is only used internally within the Switch). Untagging is
used to send packets from an 802.1Q-compliant network device to a non-compliant network
device.
Frame Income
Frame Leave
Income Frame is tagged Income Frame is untagged
Leave port is tagged Frame remains tagged Tag is inserted
Leave port is untagged Tag is removed Frame remain untagged