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ES-3100 Series Switch Support Notes

• How 802.1Q VLAN works

According to the VID information in the tag, the switch forward and filter the

frames among ports. These ports with same VID can communicate with each

other. IEEE 802.1Q VLAN function contains the following three tasks, Ingress

Process, Forwarding Process and Egress Process.

1. Ingress Process:

Each port is capable of passing tagged or untagged frames. Ingress Process

identifies if the incoming frames contain tag, and classifies the incoming frames

belonging to a VLAN. Each port has its own Ingress rule. If Ingress rule accept

tagged frames only, the switch port will drop all incoming non-tagged frames. If

Ingress rule accept all frame type, the switch port simultaneously allow the incoming

tagged and untagged frames:

• When a tagged frame is received on a port, it carries a tag header that has a

explicit VID. Ingress Process directly pass the tagged frame to Forwarding

Process.

• An untagged frame doesn't carry any VID to which it belongs. When a

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ZyXEL Communications GS-4012F Uživatelská příručka Strana 42