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This chapter is from the book

Spanning-Tree Configuration

It is crucial to understand the impact of a default switch configuration on STP convergence and what configurations can be applied to adjust the default behavior.

PVST+ and Rapid PVST+ Configuration

Complete Table 2-6 to show the default spanning-tree configuration for a Cisco Catalyst 2960 series switch.

Table 2-6 Default Switch Configuration

Feature

Default Setting

Enable state

Enabled on VLAN 1

Spanning-tree mode

Switch priority

Spanning-tree port priority (configurable on a per-interface basis)

Spanning-tree port cost (configurable on a per-interface basis)

1000 Mbps:

100 Mbps:

10 Mbps:

Spanning-tree VLAN port priority (configurable on a per-VLAN basis)

Spanning-tree VLAN port cost (configurable on a per-VLAN basis)

1000 Mbps:

100 Mbps:

10 Mbps:

Spanning-tree timers

Hello time: seconds

Forward-delay time: seconds

Maximum-aging time: seconds

Transmit hold count: BPDUs

Document the two different configuration commands that you can use to configure the bridge priority value so that the switch is root for VLAN 1. Use the value 4096 when necessary:

 

 

Record the command to verify that the local switch is now root:

S1# _____________________________

VLAN0001
  Spanning tree enabled protocol ieee
  Root ID    Priority    24577
             Address     000A.0033.3333
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    24577  (priority 24576 sys-id-ext 1)
             Address     0019.aa9e.b000
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1            Desg FWD 4        128.1    Shr
Fa0/2            Desg FWD 4        128.2    Shr

Explain the purpose of the BPDU guard feature on Cisco switches.

 

What command interface configuration command enables BPDU guard?

 

What global configuration command will configure all nontrunking ports as edge ports?

 

What global configuration command will configure BPDU guard on all PortFast-enabled ports?

 

The power of PVST+ is that it can load balance across redundant links. By default, the least-favored redundant link is not used. So, you must manually configure PVST+ to use the link.

Figure 2-5 represents a small section of Figure 2-1, showing only two distribution layer switches and one access layer switch. For this example, we have attached PC2 to S1. PC1 is assigned to VLAN 15, and PC2 is assigned to VLAN 25. D1 should be the primary root for VLAN 1 and VLAN 15 and the secondary root for VLAN 25. D2 should be the primary root for VLAN 25 and the secondary root for VLAN 15.

Figure 2-5

Figure 2-5 PVST+ Configuration Topology

Based on these requirements, document the commands to modify the default PVST+ operation on D1 and D2.

D1 commands

 

 

D2 commands

 

 

Document the commands to configure all nontrunking ports on S1 as edge ports with BPDU guard enabled.

 

Now, assume that you want to run rapid PVST+ on all three switches. What command is required?

 

Lab - Configuring Rapid PVST+, PortFast, and BPDU Guard (SN 2.3.2.3/SwN 4.3.2.3)

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Packet Tracer - Configuring PVST+ (SN 2.3.1.5/SwN 4.3.1.5)

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Packet Tracer - Configuring Rapid PVST+ (SN 2.3.2.2/SwN 4.3.2.2)

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