Enterasys Networks 6H2xx - Manual (Page 401)

Example 2, VLANs Across Multiple Switches
VLAN Operation and Network Applications 13-29
13.13.2 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 13-13 .
Figure 13-13 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 FDB ID 2 if it didn’t already have a dynamic entry
for MAC address “Y” in FDB ID 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.
Figure 13-14
shows the path taken to this point to reach Switch 2.
The VLAN Tag Header is inserted because Switch 4, Port 4 is set to transmit tagged frames.
Floor 4
2263_14
1 3
2
Bridge 1 Bridge 2
Redco Blue Industries
Red VLAN Red VLAN Blue VLAN Blue VLAN
User A
4
4