Lab 3-3 Per-VLAN Spanning Tree Behavior
Objective
The purpose of this lab is to observe what happens when there is a separate
spanning tree instance per VLAN. This lab also looks at changing spanning tree
mode to rapid spanning tree.
Scenario
Four switches have just been installed. The distribution layer switches are
Catalyst 3560s, and the access layer switches are Catalyst 2960s. There are
redundant uplinks between the access layer and distribution layer. Because of
the possibility of bridging loops, spanning tree logically removes any redundant
links. In this lab, you will see what happens when spanning tree is configured
differently for different VLANs.
Step 1
Start by deleting the vlan.dat file, erasing the startup config, and reloading all
your switches. After reloading the switches, give them hostnames. Configure
ports f0/7 through f0/12 to be trunks. On the 3560s, you first need to set the trunk
encapsulation to dot1q. On the 2960s, only dot1q is supported, so it does not
need to be set, but the mode still needs to be changed to trunk. If you do not set
the mode of the ports to trunk, the links do not form trunks and remain access
2 - 13 CCNP: Building Multilayer Switched Networks v5.0 - Lab 3-3 Copyright © 2006, Cisco Systems, Inc
ports (the default mode on a 3560 or 2960 is dynamic auto; the default mode on
a 3550 or 2950 is dynamic desirable).
DLS1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
DLS1(config)#interface range f0/7 - 12
DLS1(config-if-range)#switchport trunk encapsulation dot1q
