Cabletron Systems 802.1Q Manual De Usuario

The VLAN Tag Header is inserted because Switch 4, Port 4 is 
designated as an 802.1Q Trunk port. In this case, the Port Mode setting 
for Port 4 is 802.1Q Trunk and the VLAN Frame format for that 
VLAN is tagged.

When Switch 2 receives the tagged frame on its Port 2, it checks the 
frame’s VLAN Tag Header and determines that the frame is classified 
as belonging to the Red VLAN, and that the frame is a broadcast 
frame. Switch 2 forwards the frame to all ports in the Red VLAN 
Forwarding List excluding Port 2, which received the frame. In this 
example, the only eligible port is Port 3, which connects to Bridge 4. 
Switch 2 checks its Forwarding List, which specifies that the VLAN 
frame type for that port is untagged. Switch 2 then updates its Source 
Address Table in FID 3 for MAC address “Y” if necessary. The 
untagged frame is then transmitted out Port 3 to Bridge 4. Bridge 4 
forwards the frame out all its ports because it is a broadcast frame, and 
the server receives it as shown in 

.

Floor 2

22631_15

Floor 3

Floor 4

Bridge 1

Bridge 2

Bridge 3

Bridge 4

4

2

1

2

3

4

1

2

3