11-18
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
78-15908-01
Chapter 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports
Example VLAN Trunk Configurations
Figure 11-3 Parallel Trunk Configuration after Configuring VLAN Traffic Load-Sharing
Figure 11-3 shows that both trunks are used when the network operates normally. If one trunk link fails,
the other trunk link acts as an alternate forwarding path for the traffic previously traveling over the failed
link.
If Trunk 1 fails in the network shown in Figure 11-3, STP reconverges to use Trunk 2 to forward traffic
from all the VLANs, as shown in this example:
Switch_1> (enable) 04/21/1998,03:15:40:ETHC-5:Port 1/1 has become non-trunk
Switch_1> (enable) show spantree 1/1
Port Vlan Port-State Cost Priority Fast-Start Group-method
--------- ---- ------------- ----- -------- ---------- ------------
1/1 1 not-connected 19 32 disabled
Switch_1> (enable) show spantree 1/2
Port Vlan Port-State Cost Priority Fast-Start Group-method
--------- ---- ------------- ----- -------- ---------- ------------
1/2 1 learning 19 32 disabled
1/2 10 learning 19 32 disabled
1/2 20 learning 19 32 disabled
1/2 30 learning 19 32 disabled
1/2 40 forwarding 19 1 disabled
1/2 50 forwarding 19 1 disabled
1/2 60 forwarding 19 1 disabled
1/2 1003 not-connected 19 32 disabled
1/2 1005 not-connected 19 4 disabled
Switch_1> (enable) show spantree 1/2
Port Vlan Port-State Cost Priority Fast-Start Group-method
--------- ---- ------------- ----- -------- ---------- ------------
1/2 1 forwarding 19 32 disabled
1/2 10 forwarding 19 32 disabled
1/2 20 forwarding 19 32 disabled
1/2 30 forwarding 19 32 disabled
1/2 40 forwarding 19 1 disabled
1/2 50 forwarding 19 1 disabled
1/2 60 forwarding 19 1 disabled
1/2 1003 not-connected 19 32 disabled
1/2 1005 not-connected 19 4 disabled
Switch_1> (enable)
Catalyst 4500
Switch 1
Catalyst 4500
Switch 2
Trunk 1
VLANs 10, 20, 30, 40, 50, and 60: port-VLAN priority 32 (forwarding)
Trunk 2
VLANs 10, 20, 30, 40, 50, and 60: port-VLAN priority 32 (blocking)
99514
1/1
1/2
1/1
1/2
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