D-Link DES-3250TG User Manual page 41

•
Untagging – The act of stripping 802.1Q VLAN
information out of the packet header.
•
Ingress port – A port on a switch where packets are
flowing into the switch and VLAN decisions must be
made.
•
Egress port – A port on a switch where packets are
flowing out of the switch, either to another switch or to
an end station, and tagging decisions must be made.
IEEE 802.1Q (tagged) VLANs are implemented on the DES-
3250TG Layer 2 switch. 802.1Q VLANs require tagging, which
enables the VLANs to span an entire network (assuming all
switches on the network are IEEE 802.1Q-compliant).
Any port can be configured as either tagging or untagging. The
untagging feature of IEEE 802.1Q VLANs allow VLANs to work
with legacy switches that don't recognize VLAN tags in packet
headers. The tagging feature allows VLANs to span multiple
802.1Q-compliant
connection and allows Spanning Tree to be enabled on all ports
and work normally.
802.1Q VLAN Packet Forwarding
Packet forwarding decisions are made based upon the following
three types of rules:
•
Ingress rules – rules relevant to the classification of
received frames belonging to a VLAN.
•
Forwarding rules between ports – decides filter or
forward the packet
•
Egress rules – determines if the packet must be sent
tagged or untagged.
DES-3250TG Layer 2 Fast Ethernet Switch User's Guide
switches through
33
a single physical