10-25
Catalyst 3750 MetroSwitch Software Configuration Guide
78-15870-01
Chapter 10 Configuring VLANs
Configuring VLAN Trunks
Load Sharing Using STP Port Priorities
When two ports on the same switch form a loop, the STP port priority setting determines which port is
enabled and which port is in a blocking state. You can set the priorities on a parallel trunk port so that
the port carries all the traffic for a given VLAN. The trunk port with the higher priority (lower values)
for a VLAN is forwarding traffic for that VLAN. The trunk port with the lower priority (higher values)
for the same VLAN remains in a blocking state for that VLAN. One trunk port sends or receives all
traffic for the VLAN.
Figure 10-3 shows two trunks connecting supported switches. In this example, the switches are
configured as follows:
• VLANs 8 through 10 are assigned a port priority of 16 on Trunk 1.
• VLANs 3 through 6 retain the default port priority of 128 on Trunk 1.
• VLANs 3 through 6 are assigned a port priority of 16 on Trunk 2.
• VLANs 8 through 10 retain the default port priority of 128 on Trunk 2.
In this way, Trunk 1 carries traffic for VLANs 8 through 10, and Trunk 2 carries traffic for VLANs 3
through 6. If the active trunk fails, the trunk with the lower priority takes over and carries the traffic for
all of the VLANs. No duplication of traffic occurs over any trunk port.
Figure 10-3 Load Sharing by Using STP Port Priorities
Beginning in privileged EXEC mode, follow these steps to configure the network shown in Figure 10-3.
93370
Switch A
Switch B
Trunk 2
VLANs 3 – 6 (priority 16)
VLANs 8 – 10 (priority 128)
Trunk 1
VLANs 8 – 10 (priority 16)
VLANs 3 – 6 (priority 128)
Command Purpose
Step 1
configure terminal Enter global configuration mode on Switch A.
Step 2
vtp domain domain-name Configure a VTP administrative domain.
The domain name can be from 1 to 32 characters.
Step 3
vtp mode server Configure Switch A as the VTP server.
Step 4
end Return to privileged EXEC mode.
Step 5
show vtp status Verify the VTP configuration on both Switch A and Switch B.
In the display, check the VTP Operating Mode and the VTP Domain
Name fields.
Step 6
show vlan Verify that the VLANs exist in the database on Switch A.
Step 7
configure terminal Enter global configuration mode.
To Next Page
Loading...
Need help?
General
