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Zorluk: ZorRapid PVST+ Spanning Tree Protocol Operations and Roles

A network administrator needs to manually configure a Catalyst switch as the primary Root Bridge for VLAN 30 using Rapid PVST+. The switch currently has default STP settings. Which configuration change correctly sets the bridge priority, and what is the resulting Bridge Priority value advertised in the Bridge Protocol Data Units (BPDUs) for VLAN 30?

  1. Execute 'spanning-tree vlan 30 priority 4096'; the advertised Bridge Priority in BPDUs will be 4126.Cevap
  2. B
    Execute 'spanning-tree vlan 30 priority 4000'; the advertised Bridge Priority in BPDUs will be 4030.
  3. C
    Execute 'spanning-tree vlan 30 priority 4096'; the advertised Bridge Priority in BPDUs will be 4096.
  4. D
    Execute 'spanning-tree vlan 30 portfast trunk'; the advertised Bridge Priority in BPDUs will be 0.

Cevap

Execute 'spanning-tree vlan 30 priority 4096'; the advertised Bridge Priority in BPDUs will be 4126.
In Rapid PVST+, the Bridge ID priority consists of a 4-bit base priority and a 12-bit System ID Extension representing the VLAN ID. The command 'spanning-tree vlan 30 priority 4096' sets the base priority to a valid multiple of 4096. When combined with the System ID Extension of 30, the switch advertises a total Bridge Priority of 4126 (4096+304096 + 30) in its BPDUs.

Adım Adım Çözüm

1
Determine valid STP bridge priority configuration increments.
STP bridge priority must be configured in increments of 4096 (e.g., 0, 4096, 8192, 12288, etc.).
The 16-bit Priority field in the Bridge ID (BID) is divided into a 4-bit Priority field (multiples of 4096) and a 12-bit System ID Extension field.
2
Calculate the total advertised Bridge Priority for VLAN 30.
Base Priority (4096) + System ID Extension (VLAN 30) = 4126.
Rapid PVST+ appends the 12-bit VLAN ID to the 4-bit base priority value to form the complete 16-bit priority component of the Bridge ID.

Anahtar Kavram

Rapid PVST+ System ID Extension and Bridge Priority Calculation
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Konular

Rapid PVST+ Spanning Tree Protocol Operations and Roles

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