A network administrator is manually configuring a Cisco switch to become the root bridge f… — Cisco CCNA

A network administrator is manually configuring a Cisco switch to become the root bridge for VLAN 10 using Rapid PVST+. Which value is valid to specify with the command `spanning-tree vlan 10 priority <value>`?

24576Cevap
B
24586
C
25000
D
Enabling PortFast on the trunk link to lower priority

Cevap

The valid bridge priority setting is 24576, as Rapid PVST+ requires configurable priority values to be in increments of 4096.

In Rapid PVST+, the configurable bridge priority must be a multiple of 4096 (

0, 4096, 8192, \dots, 61440

). The value 24576 is

6 \times 4096

, making it a valid configuration parameter. The switch automatically adds the VLAN ID (10) to the base priority to create the combined Bridge Identifier priority of 24586.

Adım Adım Çözüm

Identify the Rapid PVST+ bridge priority structure requirement

Rapid PVST+ uses the 802.1t System ID Extension, dividing the 16-bit Bridge Priority field into a 4-bit priority component and a 12-bit VLAN ID component.

Because 4 bits are reserved for priority, values can only change by steps of

2^{12} = 4096

Evaluate the candidate values for multiples of 4096

24576 / 4096 = 6

, which is an exact integer multiple.

The CLI requires entering the base priority multiplier (

6 \times 4096 = 24576

), and the switch will internally add VLAN 10 to yield a total priority of 24586.

Anahtar Kavram

Rapid PVST+ Bridge Priority Increment Calculation

Tahmini Süre:45s

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