20 Hot Standby Router Protocol Interview Questions and Answers

Hot Standby Router Protocol (HSRP) is a Cisco-proprietary redundancy protocol that is used to maintain continuous availability of gateway services by providing automatic failover in the event of router or link failure. As a network engineer, you should be familiar with HSRP and be able to answer questions about it during a job interview. This article will review some common HSRP interview questions and provide tips on how to answer them.

Hot Standby Router Protocol Interview Questions and Answers

Here are 20 commonly asked Hot Standby Router Protocol interview questions and answers to prepare you for your interview:

1. What is Hot Standby Router Protocol?

Hot Standby Router Protocol (HSRP) is a Cisco-proprietary redundancy protocol that is used to maintain continuous network connectivity in the event of a router failure. HSRP is typically used in conjunction with other redundancy protocols, such as Virtual Router Redundancy Protocol (VRRP) or Gateway Load Balancing Protocol (GLBP), to provide a robust and redundant network infrastructure.

2. What are the main advantages of using HSRP?

The main advantages of using HSRP are that it is a standards-based protocol, it is widely supported, and it is very simple to configure. Additionally, HSRP provides a high level of redundancy and is very reliable.

3. Can you explain how an HSRP router knows when to assume control of the network?

When an HSRP router is configured, it is assigned a priority number. The router with the highest priority number will assume control of the network unless it goes offline, in which case the router with the next highest priority number will take over.

4. What happens if the active router fails and a standby router assumes control?

When the active router fails, the standby router will take over and assume control. This process is known as failover.

5. How do you configure preemption on an HSRP router?

To configure preemption on an HSRP router, you will need to use the “preempt” command. This command will tell the router to take over as the active router if it detects that the current active router has failed.

6. Can you list some common use cases for HSRP?

HSRP is commonly used in enterprise networks as a redundancy and failover mechanism. In particular, it is often used in conjunction with Cisco routers and switches. HSRP can also be used in other types of networks, such as service provider networks and data center networks.

7. What’s the difference between preemptive and non-preemptive modes in HSRP?

In preemptive mode, the router with the highest priority will always assume the active role, even if it is not currently the active router. In non-preemptive mode, the router with the highest priority will only assume the active role if the current active router fails.

8. Can you give me some examples of situations where it would be helpful to disable HSRP?

There are a few reasons you might want to disable HSRP. One is if you are troubleshooting another issue and want to rule out HSRP as a potential cause. Another is if you have a device that is not HSRP-compatible and you need to prevent it from trying to use the protocol. Finally, you might need to disable HSRP in order to comply with certain security policies.

9. Why do we need multiple groups in HSRP?

There are a few reasons for why we might need multiple groups in HSRP. One reason is for redundancy – if one group fails, then the other can take over. Another reason is for load balancing – if we have two groups, then we can distribute the traffic between them. Finally, we might need multiple groups if we have different types of traffic that need to be handled differently – for example, we might have one group for real-time traffic and another for non-real-time traffic.

10. What’s the default priority value used by HSRP routers? Is it possible to change this value?

The default priority value used by HSRP routers is 100. This value can be changed, and doing so can be helpful in certain situations – for example, if you want one router to always be the active router, you can give it a higher priority value.

11. How does an HSRP router know which interface to use when there are multiple interfaces available?

The HSRP router will use the interface with the lowest priority number.

12. What is the maximum number of HSRP groups allowed per interface?

The maximum number of HSRP groups allowed per interface is eight.

13. What happens if the Active HSRP router fails? Will the backup router become the new Active router automatically or will the standby router request election from other routers first before assuming control?

If the Active HSRP router fails, the backup router will automatically become the new Active router.

14. Are all HSRP routers configured with the same priority value? If not, can you explain why not?

No, all HSRP routers are not configured with the same priority value. The priority value is used to determine which router will be the active router and which router will be the standby router. The router with the highest priority value will be the active router.

15. Can you briefly explain what multicast forwarding is? How does it affect HSRP?

Multicast forwarding is the process of forwarding packets from one multicast group to another. This can be done either by using a static configuration, or by using a dynamic protocol such as HSRP. HSRP is a protocol that allows for the automatic failover of router functions in the event of a failure.

16. When configuring HSRP, should each group have its own IP address? Explain your answer?

No, each group does not need its own IP address. In fact, it is recommended that you use a single IP address for all HSRP groups. This will simplify your configuration and make it easier to manage.

17. Does HSRP support IPv6 routing?

Yes, HSRP supports IPv6 routing.

18. What is a VRRP router? How is it different from an HSRP router?

A VRRP router is a router that uses the Virtual Router Redundancy Protocol in order to provide failover capabilities in the event that the primary router goes down. An HSRP router is a router that uses the Hot Standby Router Protocol in order to provide failover capabilities in the event that the primary router goes down.

19. What’s the best way to troubleshoot connectivity issues related to HSRP?

The best way to troubleshoot connectivity issues related to HSRP is to use a packet sniffer to capture traffic on the network and look for HSRP packets. If you see HSRP packets, then you know that the protocol is running and that the issue is likely with something else on the network. If you don’t see any HSRP packets, then you know that the issue is likely with the HSRP configuration.

20. What steps can you take to optimize performance of HSRP?

There are a few things you can do to optimize performance with HSRP:

– Use a higher priority value for the router that you want to be the active router. This will ensure that it is always chosen as the active router unless it goes down.
– Use a lower priority value for the router that you want to be the standby router. This will ensure that it is only chosen as the active router if the primary router goes down.
– Use a shorter hello interval. This will cause the router to check the status of the other router more frequently, so that it can more quickly take over if the primary router goes down.
– Use a shorter hold time. This will cause the router to check the status of the other router more frequently, so that it can more quickly take over if the primary router goes down.