Four Cisco Catalyst switches (SW1, SW2, SW3, and SW4) are deployed in an enterprise network running Rapid PVST+ for VLAN 10. SW1 is elected as the Root Bridge. SW4 connects to SW2 via interface GigabitEthernet0/1 and to SW3 via interface GigabitEthernet0/2. Both paths yield an identical cumulative root path cost of 4. SW2 has a lower Bridge ID than SW3. In addition, interfaces GigabitEthernet0/3 and GigabitEthernet0/4 on SW4 are both connected to the same unmanaged hub on a single shared collision domain. Which two statements correctly describe the Rapid PVST+ port roles and state operations on SW4 for VLAN 10? (Select two.)
- GigabitEthernet0/2 is assigned the Alternate port role and operates in the Discarding state.Cevap
- GigabitEthernet0/4 is assigned the Backup port role and operates in the Discarding state.Cevap
- CGigabitEthernet0/2 is assigned the Backup port role because SW3 lost the root path cost tie-breaker to SW2.
- DGigabitEthernet0/4 transitions through the Listening state for 15 seconds before moving to the Learning state.
Cevap
The correct statements are that GigabitEthernet0/2 is assigned the Alternate port role operating in the Discarding state, and GigabitEthernet0/4 is assigned the Backup port role operating in the Discarding state.
In Rapid PVST+ (802.1w), port roles are defined based on path location and the source of BPDUs. GigabitEthernet0/1 is the Root Port because SW2 has a lower Bridge ID than SW3. GigabitEthernet0/2 receives BPDUs from another switch (SW3) offering a secondary root path, making it an Alternate port operating in the Discarding state. For GigabitEthernet0/3 and GigabitEthernet0/4 connected to the same hub, SW4 receives its own BPDUs; the port with the higher Port ID (GigabitEthernet0/4) becomes a Backup port operating in the Discarding state.
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Anahtar Kavram
Rapid PVST+ Port Roles (Root, Designated, Alternate, Backup) and States (Discarding, Learning, Forwarding)