25 Best STP Interview Questions and Answers

In this blog post, we’ll take you through 25 STP Interview Questions you can make use of before the interview process to help you find a job.

1. What is STP?

Ans. STP Stands for Spanning Tree Protocol which is a network protocol that creates redundant paths so that data can be transmitted if one or more of the links in the path becomes unavailable. This decreases delays, as packets do not have to wait until they reach each node along the way before being sent again. It also avoids loops when nodes are disabled for maintenance and does not require complex routing protocols like OSPF or IS-IS to avoid temporary traffic black holes.

2. What is a Timer in Spanning Tree Protocol?

Ans. A Timer is a value set by the switch to keep track of how long it has been since that device last heard from another. The timer starts at 0, so if a process sets its own timeout value (T) as T=120, and then waits for 120 seconds without hearing anything before declaring itself dead, each time something hears the broadcast packet with this node’s MAC address on it will reset the waiting period to 0.

3. What are the types of STP timers?

Ans. There are two types of Spanning Tree Protocol timers:

Hello Timer (default 2 seconds)

Max Age timer (default 20 seconds).

4. What does RSTP stand for?

Ans. Rapid STP stands for rapid spanning tree protocol, which was designed to solve some problems in the original STP such as convergence speed and data loss during topology changes. This new protocol helps find alternate paths quickly when there’s a link failure or if multiple links fail simultaneously.

5. What can cause an issue with TCP connections over Ethernet switches?

Ans. If you have Layer-II Ethernets running your network needs to be configured so that one port is designated as the root bridge otherwise it will default to the switch which has the most processors and this would cause an issue with TCP connections over Ethernet switches.

6. How can you configure a Spanning Tree Protocol port as an access port?

Ans. You need to set spanning-tree cost for that specific interface in order to make it a root port or designated port. The default is 32768, but you may lower it if needed (it should be at least 20000). After setting your STP priority, select “Configure” from within Interface Settings.

7. What is BPDU in STP?

Ans. The BPDUs or Bridge Protocol Data Units are the common messages exchanged between switches in an STP network. The switch uses the frames to learn about the root bridge and other switches in the area, which can then use for decision-making on where to forward data packets.

8. What do you need if you want your computer device connected via Ethernet cables starting at one end of a building or room and ending up at another end?

Ans. You need a hub or switch to connect all of your devices, and this will act as the root bridge. The switches in between will only provide data forwarding services if they’re connected to both ends of the cable that’s being used for transmission. This is because STP must maintain network loops which are caused by devices connecting at different points on topology charts.

9. What does UTP stand for?

Ans. UTP stands for Unshielded Twisted Pair found with Ethernet cables designed without metal shielding around each pair (which would cause interference). It was originally developed back in 1973 and replaced earlier twisted-pair wiring systems such as SPT-A/B for telephone communications.

10. Does Spanning Tree Protocol have any disadvantages?

Ans. One disadvantage of STP is the time it takes to recover from a topology change, and this can be as high as 50 seconds. The original protocol also had issues with data loss when there are changes in the network layout such as if an intermediate switch gets disabled or another link fails on one of the switches.

11. How does a root bridge gets elected?

Ans. The root bridge is the switch with the lowest Bridge ID (BID) out of all switches in the Layer-II Ethernet network. The BID is determined by an 802.X protocol which assigns a unique priority to each switch depending on its configuration and last reset time, but some manufacturers like Cisco assign their own identification numbers for this purpose so the new protocol can be used on legacy equipment.

12. How is a topology change handled by Spanning Tree Protocol?

Ans. If there’s an issue with one of the links in your Layer-II network, STP will have to recalculate the path and this process may take as long as 50 seconds. The original version of 802.X had an issue with data loss when there are changes in the network layout, but this is fixed by Rapid STP.

13. What are some common mistakes that can be made during a Spanning Tree Protocol installation?

Ans. You may have important printers or devices connected to ports not designated as access ports if you’re configuring your Ethernet switch and forgetting about connecting the endpoints.

14. What is the routing protocol used in Ethernet networks?

Ans. The distance-vector algorithm RIP (Routing Information Protocol) was originally used with Layer II Ethernets back in 1978 and it still retains many of its original characteristics such as using hop count to determine the best path available for data packets. The newest version, which you may have to use if you’re using a large network, is what’s known as EIGRP for both IP and AppleTalk.

15. What are some common problems with Spanning Tree Protocol implementations?

Ans. One problem that can be fixed by Rapid STP is the lack of protection against data loss when a topology change occurs in Layer-II networks.

16. What are the benefits of using Rapid Spanning Tree Protocol?

Ans. One benefit of RSTP is that it can recover from a topology change in less than one second, and this has been found to be helpful when troubleshooting network problems. The original version had some issues with data loss but these have since been fixed. It also has a few other benefits such as preventing loops that are created by devices connecting at different points on topology charts.

17. What is the disadvantage of using Rapid Spanning Tree Protocol?

Ans. One downside to RSTP is that it might not work with legacy equipment and sometimes requires changes in software or firmware, but this will vary from manufacturer to manufacturer.

18. What is a Port Number?

Ans. A port number is the identification of a data transfer point. It identifies what service type will be used to send or receive data.

19. What is a Port Range?

Ans. A port range identifies the set of ports that will be used to transfer data related to that service type.

20. What is a Root port?

Ans. The Root Port is the switch with the lowest cost out of all available ports in a Layer-II Ethernet network. The port that’s used for data flow will change if there are changes to the topology, and it’ll use its own forwarding information base (FIB) so other switches know which ports can be used as alternate paths when there are problems.

21. What is a Designated Port?

Ans. A designated port is a port in the host or network that has been assigned to transfer data related to one designated service type.

22. What is a Non-designated Port?

Ans. Non-Designated Ports are ports that have been determined to be unused by the Spanning Tree Protocol and it’s up to each network administrator in charge of setting up STP on their Ethernet switch how they want these configured. This option can range from blocking them with access lists to configuring them as a Loopback.

23. What is the Plurality?

Ans. If there’s a tie for Root Bridge ID (BID) then it’ll be broken by determining which bridge has more of these ports on it and this will result in that one being designated as Root. This sounds like something you’re going to want if there’s a tie.

24. What is the Lowest Cost?

Ans. The lowest cost will be determined by the number of data packets that have been transmitted and received from a port.

25. What is the Priority value?

Ans. When it comes to configuring your Ethernet switches so that one has better access to data packets, the Priority value will be used. This is a 16-bit number that you can assign as needed so that one port has a higher priority than another.

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