AES-100 User’s Guide

Forwarding Process Example

The switch uses the SVLAN in making frame-forwarding decisions.

First the switch checks the MAC address in a frames header against the MAC filtering database.

Next the switch checks the VLAN ID (VID) of tagged frames or assigns temporary VIDs to untagged frames (see the PVID Command).

The switch then checks the VID in a frame’s tag against the SVLAN table.

The switch notes what the SVLAN table says (that is, the SVLAN tells the switch whether or not to forward a frame and if the forwarded frames should have tags).

Then the switch applies the port filter to finish the forwarding decision. This means that frames may be dropped even if the SVLAN says to forward them. Frames might also be dropped if they are sent to an ADSL CPE device that does not accept tagged frames.

The following figure shows the flow of the decision process used with a broadcast frame (one that is meant to go to all of the ports).

Figure 8-4 SVLAN Example

An untagged frame comes in from the LAN.

The switch checks the PVID table and assigns a temporary VID of 1.

The switch ignores port# 1 (the LAN port where the frame came in), because the switch does not send a frame to the port that it came in through.

IEEE 802.1Q Tagged VLAN Commands

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