Exam 350-401 topic 1 question 887 discussion

It's A. Tracked objects will decrement priority by 10 as the default action, so that doesn't need to be explicitly configured. R2 will not become the active router without "standby preempt" unless R1 goes down completely, as f490efc mentioned, so that *does* need to be set. The scenario in this question, along with the above explanation, are mirrored here: https://www.cisco.com/c/en/us/support/docs/ip/hot-standby-router-protocol-hsrp/13780-6.html#toc-hId-1284746180

Agree with A. Decrement 10 is default value so you dont need to specify. However, R2 won't takeover unless R1 does not go down completely.

If R1's priority changes due to tracking (for example, it detects a failure on an interface and lowers its priority), R2 could temporarily become the active router if R1's priority becomes lower than R2's. If R1 recovers and its priority is restored to a higher value, R2 will not automatically revert to standby mode unless preempt is enabled on R2. Configuring preempt on R2 ensures that it will not continue acting as the active router if R1 comes back with a higher priority.

Without preemption, R2 will become the active router only if interface Gi 0/0 of R2 goes down (the interface participating in HSRP.)

standby 100 preempt: This command allows R2 to take over the role of the active router when its priority becomes higher than R1's

A is correct

C would work if it was on R1...

https://www.cisco.com/c/en/us/support/docs/ip/hot-standby-router-protocol-hsrp/13780-6.html#:~:text=The%20standby%20trackcommand%20allows%20you,the%20HSRP%20priority%20is%20reduced. The standby trackcommand allows you to specify another interface on the router for the HSRP process to monitor in order to alter the HSRP priority for a given group. If the line protocol of the specified interface goes down, the HSRP priority is reduced. This means that another HSRP router with higher priority can become the active router if that router has the standby preempt enabled. standby 1 track Serial0 !--- Indicates that HSRP tracks Serial0 interface. !--- The interface priority can also be configured, which indicates the !--- amount by which the router priority decreases when !--- the interface goes down. The default is 10.

I'm going with the option C considering the Track 26 command already applied on R1 "standby 100 track 26". The command instructs R2 to track the same interface (Serial0/0.1 with the number 26) as R1. When this tracked interface goes down on R1, both routers will adjust their HSRP priorities accordingly, facilitating a smooth failover to R2 if needed.

R2# standby 100 track 26 decrement 10