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Objective 2.5

200-301

Interpret basic operations of Rapid PVST+ Spanning Tree Protocol.

Objective 2.5 sits in Network Access, which carries 20% of the CCNA exam. The questions below are original, written from the official objective title above, and each explanation cites the Cisco page it rests on.

Objective title verbatim from the official objectives. Cisco exam page ↗

A worked example

Shown solved, with the whole explanation open: this is what every question here carries.

2-5Network Access

Two switches run Rapid PVST+ in VLAN 10 and no priority was ever configured on either.

SW1# show spanning-tree vlan 10 VLAN0010  Spanning tree enabled protocol rstp  Root ID    Priority    32778             Address     0c29.3a11.4000             This bridge is the root             Hello Time 2 sec  Max Age 20 sec  Forward Delay 15 sec   Bridge ID  Priority    32778  (priority 32768 sys-id-ext 10)             Address     0c29.3a11.4000 SW2# show spanning-tree vlan 10 VLAN0010  Spanning tree enabled protocol rstp  Root ID    Priority    32778             Address     0c29.3a11.4000             Cost        4             Port        24 (GigabitEthernet1/0/24)   Bridge ID  Priority    32778  (priority 32768 sys-id-ext 10)             Address     4c77.6d22.8000

What settled the election?

The switch with more forwarding ports took the rolePort count never enters the comparison. A switch with one link can be the root.
The lower bridge MAC address settled a priority tieCorrect · your answerCorrect. With the priorities equal, the lower hardware address wins.
The switch that sent the first BPDU claimed the roleTiming has no standing here. Every switch claims the role at power-up and yields once it hears a better advertisement.
The lower accumulated path cost decided the outcomeCost selects a root port on a switch that has already lost the election. It does not choose the winner.

Correct.

Checked against cisco.com, August 2026

Concept

The identifier a switch advertises for a VLAN is built from a configurable field and a hardware field, and it is compared as one number. When nobody has changed the configurable half, every candidate advertises the same leading value and the comparison falls through to the hardware half, which is unique per switch.

Why B

Both bridges advertise 32778, so the configurable half is identical and cannot separate them. The remaining field decides, and 0c29.3a11.4000 sorts below 4c77.6d22.8000, which is why that switch reports itself as the root and its peer reports a cost and a root port.

Source

For each VLAN, the device with the highest device priority (the lowest numerical priority value) is elected as the root switch. If all devices are configured with the default priority (32768), the devices with the lowest MAC address in the VLAN becomes the root device.

Cisco: Configuring Spanning Tree Protocol (Catalyst 9300, IOS XE 17.3.x), checked August 2026
#rapid-pvst#root-bridge#bridge-id

Now you: objective 2.5 questions

No account needed. The explanation opens when you answer.

Sample question 1 of 3

2-5Network Access

An access switch has two uplinks into the distribution layer and one client-facing port in VLAN 20.

SW3# show spanning-tree vlan 20 VLAN0020  Spanning tree enabled protocol rstp  Root ID    Priority    24596             Address     0c29.3a11.4000             Cost        4             Port        23 (GigabitEthernet1/0/23) Interface           Role Sts Cost      Prio.Nbr Type------------------- ---- --- --------- -------- --------------Gi1/0/23            Root FWD 4         128.23   P2pGi1/0/24            Altn BLK 4         128.24   P2pGi1/0/5             Desg FWD 4         128.5    P2p

What does the Gi1/0/24 role mean?

Sample question 2 of 3

2-5Network Access

An engineer set one non-default spanning-tree value on this switch for VLAN 40 and now reads the output back.

SW1# show spanning-tree vlan 40 VLAN0040  Spanning tree enabled protocol rstp  Root ID    Priority    24616             Address     0c29.3a11.4000             This bridge is the root   Bridge ID  Priority    24616  (priority 24576 sys-id-ext 40)             Address     0c29.3a11.4000

What produces the 24616 figure?

Sample question 3 of 3

2-5Network Access

One switch has two ports on the same shared segment. One forwards, the other is held down and would take over if the first failed. What role does the held down port carry?

That’s 3 of the full CCNA bank.

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Read the sources

These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.

More objectives in Network Access