Category Archives: Switching

STP Question?

1. What is SPT?
2. What is BPDU?
3. BPDU send’s update every?
4. Criteria to be a root bridge?
5. What mac address are we using to BID?
7. If we have 15 vlan how many instance we create on PVST?
8. RSTP?
9. If we have 15 vlan how many instance we create on RPVST?
10. MST?
11. In MST can we group specific vlan on a specific instance?
12. PVST, RPVST and MST are the interoperable with each other? But ideally is it good on production? Why?
13. Who will be the block port on SW1? and Why?
14. Speed cost of 10G, 1G, 1F and 1E?
15. Can we manually change hello interval of BPDU?
16. Can we eliminate waiting process (Learning, Listening, Forwarding and Blocking) and how?
17. We know that we can use portfast on access port but can we use it on trunk?
18. What is BPDUGuard?
19. BPDU Filter?
20. Root Guard?
21. Loop Guard?
22. What is P2P2 Edge on STP?
23. How do we turnoff sending BDPU on a interface?


1. Loop prevention mechanism. Block’s the parallel port.
2. Bridge protocol data unit and has the information of actual BID (Priority and Mac)
3. BPDU send’s every 2 sec
4. Lowest Bridge ID
5. Based mac address on the switch
6. Per vlan spanning tree create a instance per vlan
7. 15 instances of spanning tree
8. Rapid spanning tree improve convergence tim
9. 15 instance
10. Multiple spanning protocol standard based
11. Yes
12. Yes, No because we want single solution and consistent to our domain
13. F0/2 since this is not the lowest port. Because SW0 and SW1 sending same Cost, BID and Priority we will elect RP via lowest advertised ports and not the local port.
14. 10G – 2 , 1G – 4, 1F -19 and 1E – 100
15. Yes
16. Yes by using Portfast
17. Yes. But it’s dangerous to enable portfast on trust it could cause temporary loop while STP converge.
18. What BPDUGuard does is if port received incoming BPDU it will be on errdisable.
19. Switch stop sending BDPU
20. Secure root bridge on specific domain
21. NA
22. Edge is the dead end or It means configured as portfast
23. Spanning bpdufilter enable on interface