FGSW-2620VM User’s Manual
Bridge ID = 15
Port 3
Port 1
Port 2
A
Bridge ID = 20
Port 1
Port 2
Port 3
C
Bridge ID = 30
Port 1
Port 2
Port 3
B
LAN 1
LAN 2
LAN 3
Portcast = 19
Portcast = 19
Portcast = 19
Portcast = 4
Portcast = 4
Portcast = 19
Portcast = 4
Portcast = 4
Before Applying the STA Rules
In this example, only the default STP values are used.
Root Bridge
Port 3
Port 1
Port 2
A
Designated Bridge
Port 1
Port 2
Port 3
C
Port 1
Port 2
Port 3
B
LAN 1
LAN 2
LAN 3
Designated Port
Root Port
Root Port
Designated Port
Blocked
After Applying the STA Rules
The switch with the lowest Bridge ID (switch C) was elected the root bridge, and the ports were selected to give a high
port cost between switches B and C. The two (optional) Gigabit ports (default port cost = 4) on switch A are connected to
one (optional) Gigabit port on both switch B and C. The redundant link between switch B and C is deliberately chosen as
a 100 Mbps Fast Ethernet link (default port cost = 19). Gigabit ports could be used, but the port cost should be increased
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