Amer Networks SS3GR24i - Manual (Page 34)

SS3GR24i/SS3GR48i Layer3 Stackable Gigabit Switch User’s Guide
IEEE 802.1Q VLANs
Definition of terms:
Tagging - The act of putting 802.1Q VLAN information into the
header of a packet.
Untagging - The act of stripping 802.1Q VLAN information
from the 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 SS3GR4i
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 VLAN compliant Switches through a single physical
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.
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