Cabletron Systems 802.1Q VLAN User Manual page 75

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.
Redco
User A
Floor 4
Floor 3
Blue Industries
Floor 2
3. 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
802.1Q VLAN User's Guide
Example 2, VLANs Across Multiple Switches
2
Bridge 1
1
4
Red VLAN
Red VLAN
4
2
Bridge 3
1
2
Blue VLAN
Blue VLAN
Figure 4-5 Transmitting to Switch 4
Blue Industries
Bridge 2
3
Blue VLAN
Blue VLAN
Redco
Bridge 4
3
Red VLAN
Red VLAN
Figure 4-6.
File Server
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