Switches A and C are running PVST+ STP, and switch B is running 802.1Q STP, if the BPDU of the root in VLAN 1 is better than the BPDU of the root in VLAN 2, then there is no blocking port in the VLAN 2 topology. The BPDU of VLAN 2 never makes a full circle around the topology, it is replaced by the VLAN 1 BPDU on the B_C link, because B runs only one STP merged with VLAN ! STP of PVST+ Thus, there is a forwarding loop What does PVST+ do to correct this?
A. Switch A sends PVST+BPDUs of VLAN 2 (to the SSTP address that is flooded by switch B) towards Switch C. Switch C will put port C-B into a type-inconsistent, which prevents the loop
B. Switch B sends PVST+BPDUs of VLAN 1 (to the SSTP address that is flooded by switch A) towards Switch C. Switch C will put port C-B into a type-inconsistent, which prevents the loop
C. Switch C sends PVST+BPDUs of VLAN 2 (to the SSTP address that is flooded by switch B) towards Switch C. Switch C will put port C-B into a type-inconsistent, which prevents the loop
D. Switch A sends PVST+BPDUs of VLAN 1 (to the SSTP address that is flooded by switch B) towards Switch B. Switch A will put port C-B into a type-inconsistent, which prevents the loop “Pass Any Exam. Any Time.” – www.actualtests.com 21 Cisco 642-384: Practice Exam
Answer:A
Switches A and C are running PVST+ STP, and switch B is running 802.1Q STP, if the BPDU of the root in VLAN 1 is better than the BPDU of the root in VLAN 2, then there is no blocking port in the VLAN 2 topology. The BPDU of VLAN 2 never makes a full circle around the topology, it is replaced by the VLAN 1 BPDU on the B_C link, because B runs only one STP merged with VLAN ! STP of PVST+ Thus, there is a forwarding loop What does PVST+ do to correct this?
A. Switch A sends PVST+BPDUs of VLAN 2 (to the SSTP address that is flooded by switch B) towards Switch C. Switch C will put port C-B into a type-inconsistent, which prevents the loop B. Switch B sends PVST+BPDUs of VLAN 1 (to the SSTP address that is flooded by switch A) towards Switch C. Switch C will put port C-B into a type-inconsistent, which prevents the loop C. Switch C sends PVST+BPDUs of VLAN 2 (to the SSTP address that is flooded by switch B) towards Switch C. Switch C will put port C-B into a type-inconsistent, which prevents the loop D. Switch A sends PVST+BPDUs of VLAN 1 (to the SSTP address that is flooded by switch B) towards Switch B. Switch A will put port C-B into a type-inconsistent, which prevents the loop “Pass Any Exam. Any Time.” – www.actualtests.com 21 Cisco 642-384: Practice Exam