HSRP Questions

Here you will find answers to Hot Standby Router Protocol (HSRP) Questions

Question 1

Which protocol specified by RFC 2281 provides network redundancy for IP networks, ensuring that user traffic immediately and transparently recovers from first-hop failures in network edge devices or access circuits?

A. ICMP
B. IRDP
C. HSRP
D. STP

Answer: C

Explanation

HSRP is a Cisco-proprietary protocol developed to allow several routers or multilayer switches to appear as a single gateway IP address. This protocol is described in RFC 2281.

Question 2

Which of the following HSRP router states does an active router enter when it is preempted by a higher priority router?

A. active
B. speak
C. learn
D. listen
E. init
F. standby

Answer: B

Explanation

First we should review all the HSRP States:

State	Description
Initial	This is the beginning state. It indicates HSRP is not running. It happens when the configuration changes or the interface is first turned on
Listen	The router knows both IP and MAC address of the virtual router but it is not the active or standby router. For example, if there are 3 routers in HSRP group, the router which is not in active or standby state will remain in listen state.
Speak	The router sends periodic HSRP hellos and participates in the election of the active or standby router.
Standby	In this state, the router monitors hellos from the active router and it will take the active state when the current active router fails (no packets heard from active router)
Active	The router forwards packets that are sent to the HSRP group. The router also sends periodic hello messages

Now let’s take an example of a router passing through these states. Suppose there are 2 routers A and B in the network; router A is turned on first. It enters the initial state. Then it moves to listen state in which it tries to hear if there are already active or standby routers for this group. After learning no one take the active or standby state, it determines to take part in the election by moving to speak state. Now it starts sending hello messages containing its priority. These messages are sent to the multicast address 224.0.0.2 (which can be heard by all members in that group). When it does not hear a hello message with a higher priority it assumes the role of active router and moves to active state. In this state, it continues sending out periodic hello messages.

Now router B is turned on. It also goes through initial and listen state. In listen state, it learns that router A has been already the active router and no other router is taking standby role so it enters speak state to compete for the standby router -> it promotes itself as standby router.

Now to our main question! We want router B to become active router so we set a higher priority number than the priority of A and ask router B to take over the role of active router (with the preempt command). Now router A will fall back to the speak state to compete for active or standby state -> it becomes standby router because its priority is now lower than that of router A. (Therefore answer B is correct).

Note: Suppose router A is in active state while router B is in standby state. If router B does not hear hello messages from router A within the holdtime, router B goes into speak state to announce its priority to all HSRP members and compete for the active state. But if at some time it receives a message from the active router that has a lower priority than its priority (because the administrator change the priority in either router), it can take over the active role by sending out a hello packet with parameters indicating it wants to take over the active router. This is called a coup hello message.

(Reference and good resource: http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a91.shtml)

Question 3

Which three statements are true of a default HSRP configuration? (Choose three)

A. The Standby hello time is 2 seconds.
B. Two HSRP groups are configured.
C. The Standby track interface priority decrement is 10.
D. The Standby hold time is 10 seconds
E. The Standby priority is 100.
F. The Standby delay is 3 seconds.

Answer: C D E

Explanation

The table below shows the default values of popular HSRP parameters:

Feature	Default Setting
Standby group number	0
Standby MAC address	System assigned as: 0000.0c07.acXX, where XX is the HSRP group number
Standby priority	100
Standby delay	0 (no delay)
Standby track interface priority	10
Standby hello time	3 seconds
Standby holdtime	10 seconds

Note:

* Standby delay: If router A is the HSRP active router and then loses a link, which causes it to become standby router, and then the link comes back, the delay command causes router A to wait before it becomes active again. For example, with the “standby preempt delay minimum 30” command, it waits for 30 seconds for the router to become active.

* Standby track: For example, consider this configuration:
standby priority 150
standby track serial 0

An HSRP priority of 150 is configured with the standby priority command and HSRP is configured to track the state of interface Serial0. Because no decrement value is specified in the standby track command, the HSRP priority is decremented by the default value of 10 when the tracked interface goes down.

(Reference: http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_12c_ea1/configuration/guide/swhsrp.html)

Question 4

hostname Switch1 interface Vlan10 ip address 172.16.10.32 255.255.255.0 no ip redirects standby 1 ip 172.16.10.110 standby 1 timers 1 5 standby 1 priority 130 hostname Switch2 interface Vlan10 ip address 172.16.10.33 255.255.255.0 no ip redirects standby 1 ip 172.16.10.110 standby 1 timers 1 5 standby 1 priority 120

HSRP was implemented and configured on two switches while scheduled network maintenance was performed.
After the two switches have finished rebooting, you notice via show commands that Switch2 is the HSRP active router. Which two items are most likely the cause of Switch1 not becoming the active router? (Choose two)

A. booting delays
B. standby group number does not match VLAN number
C. IP addressing is incorrect
D. premption is disabled
E. incorrect standby timers
F. IP redirect is disabled

Answer: A D

Explanation

When two routers are turned on at the same time, the router completes booting process first will take the active role. Without the “preempt” configured, even a new router with a higher priority cannot take over the active role.In the configuration of Switch1 we don’t see the “preempt” command configured.

Question 5

hostname Switch1 interface Vlan10 ip address 172.16.10.32 255.255.255.0 no ip redirects standby 1 ip 172.16.10.110 standby 1 timers msec 200 msec 700 standby 1 preempt

hostname Switch2 interface Vlan10 ip address 172.16.10.33 255.255.255.0 no ip redirects standby 1 ip 172.16.10.110 standby 1 timers msec 200 msec 750 standby 1 priority 110 standby 1 preempt

hostname Switch3 interface Vlan10 ip address 172.16.10.34 255.255.255.0 no ip redirects standby 1 ip 172.16.10.110 standby 1 timers msec 200 msec 750 standby 1 priority 150 standby 1 preempt

Refer to the exhibit. Three switches are configured for HSRP. Switch1 remains in the HSRP listen state. What is the most likely cause of this status?

A. this is normal operation
B. standby group number does not match VLAN number
C. IP addressing is incorrect
D. incorrect priority commands
E. incorrect standby timers

Answer: A

Explanation

Only Switch 1 is not configured with the priority so it will have the default priority of 100, which is smaller than that of Switch2 (110) and Switch3 (150). Moreover, both Switch2 and Switch3 have the “preempt” command so surely Switch3 becomes active router while Switch2 becomes standby router -> Switch1 will be in listen state (Please read the explanation of question 2 to understand more about this state).

Question 6

What are three possible router states of HSRP routers on a LAN? (Choose three)

A. Standby
B. Established
C. Active
D. Idle
E. Backup
F. Init

Answer: A C F

Explanation

Same as Question 2

Question 7

Refer to the exhibit. Which configuration on the HSRP neighboring device ensures that it becomes the active HSRP device in the event that port fa1/1 on Switch_A goes down?

Switch_A(config-if)# ip address 10.10.10.1 255.255.255.0 Switch_A(config-if)# standby 1 priority 200 Switch_A(config-if)# standby 1 preempt Switch_A(config-if)# standby 1 track interface fa 1/1 Switch_A(config-if)# standby 1 ip 10.10.10.10

A.
Switch_B(config-if)#ip address 10.10.10.2 255.255.255.0
Switch_B(config-if)#standby 1 priority 200
Switch_B(config-if)#standby 1 preempt
Switch_B(config-if)#standby 1 ip 10.10.10.10
Switch_B(config-if)#standby 1 track interface fa 1/1

B.
Switch_B(config-if)#ip address 10.10.10.2 255.255.255.0
Switch_B(config-if)#standby 1 priority 200
Switch_B(config-if)#standby 1 ip 10.10.10.10

C.
Switch_B(config-if)#ip address 10.10.10.2 255.255.255.0
Switch_B(config-if)#standby 1 priority 195
Switch_B(config-if)#standby 1 preempt
Switch_B(config-if)#standby 1 ip 10.10.10.10

D.
Switch_B(config-if)#ip address 10.10.10.2 255.255.255.0
Switch_B(config-if)#standby 1 priority 190
Switch_B(config-if)#standby 1 ip 10.10.10.10
Switch_B(config-if)#standby 1 track interface fa 1/1

Answer: C

Explanation

Switch_A is not configured standby track priority value so it will use the default track priority of 10 -> When Switch_A goes down, its priority is 200 – 10 = 190 so Switch_B must be configured with a priority higher than 190. Also Switch_B must have the “preempt” command configured to take over the active state -> C is correct.

Note: Answer A is not correct because Switch_B has the same priority value of Switch_A, but the Switch_B’s ip address on the HSRP interface is higher (10.10.10.2 is higher than 10.10.10.1) so Switch_B will take over the active state of Switch_A even when Switch_A is still operational.

Question 8

Which two statements about the HSRP priority are true? (Choose two)

A. To assign the HSRP router priority in a standby group, the standby group-number priority priority-value global configuration command must be used.
B. The default priority of a router is zero (0).
C. The no standby priority command assigns a priority of 100 to the router.
D. Assuming that preempting has also been configured, the router with the lowest priority in an HSRP group would become the active router.
E. When two routers in an HSRP standby group are configured with identical priorities, the router with the highest configured IP address will become the active router.

Answer: C E

Explanation

The “no standby priority” command will reset the priority to the default value (100) -> C is correct.

To understand answer E please read the explanation of Question 7.

Question 9

HSRP has been configured between two Company devices. Which of the following describe reasons for deploying HSRP? (Choose three)

A. HSRP provides redundancy and fault tolerance
B. HSRP allows one router to automatically assume the function of the second router if the second router fails
C. HSRP allows one router to automatically assume the function of the second router if the second router starts
D. HSRP provides redundancy and load balancing

Answer: A B D

Explanation

Answer A and B are correct because they are the functions of HSRP. I just want to mention about answer D. In fact answer D is not totally correct, in SWITCH only GLBP has the load-balancing feature. HSRP can only load-sharing by configuring some different HSRP groups. But answer D is the only choice left in this question so we have to choose it.

Question 10

Regarding high availability, with the MAC address 0000.0c07.ac03, what does the “03″ represent?

A. The GLBP group number
B. The type of encapsulation
C. The HSRP router number
D. The VRRP group number
E. The HSRP group number
F. The active router number

Answer: E

Explanation

The last two-digit hex value in the MAC address presents the HSRP group number.