Exam JN0-649 topic 1 question 49 discussion

D is wrong. https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/statement/bridge-priority-edit-protocols-stp.html#bridge-priority__d439122e195

B,D D. Default VSTP bridge priority values are configured. ✅ Correct The bridge priorities shown are 4106 (VLAN 10) and 4116 (VLAN 20). The default bridge priority in Juniper's VSTP (VLAN Spanning Tree Protocol) is 4096 + VLAN ID. Here: VLAN 10: 4096 + 10 = 4106 (matches) VLAN 20: 4096 + 20 = 4116 (matches) This confirms that default bridge priority values are used

Default VSTP priority is 32k so D is wrong

100% it is B, D. No doubt for B. BPDUs from the root bridge for VLAN 20 are received on port Ge-0/0/8 - root port. Root port is the closest port to the root bridge -> the best BPDUs are received on root port. D - 4096 is default priority + VLAN Number => 4106 for Vlan 10 and 4116 for Vlan 20

bc is correct

should be BC

If a non-root bridge receives a BPDU (Bridge Protocol Data Unit) from the root bridge on one of its ports, it will use the information contained in the BPDU to determine the root bridge and calculate the best path to reach it. The non-root bridge will compare the received BPDU's root bridge ID with its own bridge ID. If the root bridge ID in the received BPDU is lower than the bridge ID of the non-root bridge, the non-root bridge will understand that there is a better path to reach the root bridge through the port where the BPDU was received. This port will become the root port. Once the root port is selected, the non-root bridge will forward all traffic destined for the root bridge through this port. The non-root bridge will also send its own BPDU's out all other ports to help maintain the spanning tree topology and ensure that loops do not occur in the network. In summary, when a non-root bridge receives a BPDU from the root bridge, it uses the information in the BPDU to select its root port and forward traffic towards the root bridge.

B - as all ports are designated C- BPDU also received on blocked ports

No doubt for B. C is absolutely wrong, the ROOT port on an non-root bridge receives BPDU from root bridge, so for vlan 20 the port receives BPDU is ge-0/0/8.0 not ge-0/0/7.0

i think b and c

DS-1 port status - DESG / FWD - VLAN 10 - ROOT Bridge DS-1 port status BLK/ALT - VLAN 20