Refer to the exhibit. Switches A and C are running PVST+ STP, and Switch B is running 802.10 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 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 1 STP of PVST+. Thus, there is a forwardin 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 state, 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 state, 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 A will put port C.B into a typE.inconsistent state, 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 state, which prevents the loop.
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 state, which prevents the loop.
E.
Switch C sends PVST+ BPDUs of VLAN 2 (to the SSTP address that is flooded by Switch B) towards Switch C. Switch A will put port C.B into a typE.inconsistent state, which prevents the loop.
F.
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 state, which prevents the loop.