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Example 2, VLANs Across Multiple Switches
12.13.2 Frame Handling
The following describes how, when User A attempts to log on to the File Server on Bridge 4, the
frames from User A are classified on Switch 4 and traverse the network. In this example, the MAC
address of User A is "Y" and the MAC address for the File Server is "Z". The following
description includes illustrations to help understand how the frames flow through the network.
1. User A sends a frame with a Broadcast Destination Address in an attempt to locate the File
Server. The frame is received on User A's port of Bridge 1 and, because the frame is a broadcast
frame, it is transmitted out all ports of Bridge 1 as shown in
Figure 12-15 Bridge 1 Broadcasts Frames
2. Switch 4 receives the frame from Bridge 1 and immediately classifies it as belonging to the Red
VLAN. After the frame is classified, Switch 4 checks the Destination Address and, upon
discovering that it is a Broadcast Destination Address, forwards the frame out all ports in the
Red VLAN Forwarding List excluding Port 1, which received the frame. In this example, it is
only Port 4.
Switch 4 updates its Source Address Table in FID 2 if it didn't already have a dynamic entry for
MAC address "Y" in FID 2. Because Switch 4 received the frame on Port 1, it does not forward
the frame out that port, but does forward the frame to Port 4.
The frame is transmitted to Switch 2 with a VLAN Tag Header inserted in the frame. The VLAN
Tag Header indicates that the frame is classified as belonging to the Red VLAN.
shows the path taken to this point to reach Switch 2.
12-28
VLAN Operation and Network Applications
Figure
12-15.
Figure 12-16
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