Scenario 5: Advanced STP

A small network consists of two core switches, Catalyst C1 and C2, and an access switch, A1, as shown in Figure 19-5. Advanced Spanning Tree Protocol features will improve the convergence times and reduce the number of STP instances. Answer these questions.

Figure 19-5. Network Diagram for Scenario 5

1.	To prevent the possibility of a unidirectional link occurring on switch A1's uplinks, what switch feature can be used? What commands are necessary to enable this feature? Assume that the links should be disabled if a unidirectional condition is found. Which switches need to be configured this way?
2.	On Catalyst A1, what feature and command should be used to prevent unexpected STP BPDUs from being received on the ports connected to end users?
3.	For the links between switch A1 and the user PCs, what command is needed to configure these as RSTP edge ports?
4.	By default, the traditional PVST+ mode is enabled on a switch. What command can be used to enable RSTP to be used with PVST+?
5.	Suppose that MST is to be configured to reduce the number of STP instances because 12 unique VLANs are being used across the network. How many MST instances are needed for the three switches shown in Figure 21-4, assuming that traffic should be load-balanced across the two uplinks of switch A1?
6.	What commands are needed to configure switch C1 for MST?
7.	Now make sure that C1 is configured as the root bridge for one MST instance. What commands are needed?