CCNA IP Routing Practice Question
Exhibit
R1# show standby brief
P indicates configured to preempt.
|
Interface Grp Pri P State Active Standby Virtual IP
Vlan10 10 110 Active local 192.168.10.2 192.168.10.1
R2# show standby brief
P indicates configured to preempt.
|
Interface Grp Pri P State Active Standby Virtual IP
Vlan10 20 100 Active local unknown 192.168.10.1Two routers, R1 and R2, have been configured with HSRP for VLAN 10 to provide default gateway redundancy to hosts. The virtual IP address is 192.168.10.1. After configuration, end hosts report inconsistent connectivity to the gateway, and a failover test reveals that when the active router is shut down, connectivity is lost. The network administrator checks the HSRP status on both routers. R1 shows HSRP group 10 as Active with no standby router, and R2 shows HSRP group 20 as Active with no standby router. What is the most likely cause of the redundancy failure?
⚠ Common exam trap
Cisco often tests the HSRP group number mismatch as a subtle cause of redundancy failure because candidates focus on priority or authentication and overlook the fundamental requirement that the group number must be identical on all routers in the same virtual router group.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The HSRP group number is mismatched between R1 and R2.
HSRP requires all routers participating in the same virtual router to use the same group number. Because R1 is active for group 10 and R2 is active for group 20, neither router has a standby for its group. If the active router for a group fails, no standby router can take over, causing loss of connectivity. Authentication mismatch or HSRP version mismatch would typically prevent routers from forming a neighbor relationship, but the provided status showing each router active in a different group points specifically to a group mismatch.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
R2 has a lower HSRP priority than R1, so it cannot become standby.
Why it's wrong here
A lower priority does not prevent a router from becoming standby; it simply makes it less likely to become the active router if preemption is enabled. Here the issue is not priority—both routers are active in different groups.
- ✓
The HSRP group number is mismatched between R1 and R2.
Why this is correct
HSRP group numbers define distinct virtual router instances; R1 is active for group 10 with virtual IP 10.1.1.10, while R2 is active for group 20 with virtual IP 10.1.1.20. Because they belong to different groups, neither router accepts or processes the other's hello packets, so they form separate HSRP domains with no shared virtual MAC address. Consequently, the standby router cannot take over if the active fails, which is exactly the redundancy failure observed.
- ✗
The HSRP authentication strings do not match.
Why it's wrong here
HSRP authentication mismatch would cause the routers to reject each other's hello messages, but the routers would still be configured with the same group number. The failure symptom would be both routers attempting to become active for the same group (or remaining in a non-active state), not the group 10 vs. group 20 configuration seen in the outputs. Since the show standby output explicitly displays different group numbers, authentication is not the root cause; the group mismatch fully explains the lack of failover.
- ✗
HSRP version 1 is used on R1 while version 2 is used on R2.
Why it's wrong here
A version mismatch would cause the routers to ignore each other’s hello packets and both become active, but they would still be in the same configured group number. The output shows different group numbers (10 vs 20), which is a more explicit misconfiguration.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The HSRP group number is mismatched between R1 and R2.Correct answer▾
Why this is correct
HSRP group numbers define distinct virtual router instances; R1 is active for group 10 with virtual IP 10.1.1.10, while R2 is active for group 20 with virtual IP 10.1.1.20. Because they belong to different groups, neither router accepts or processes the other's hello packets, so they form separate HSRP domains with no shared virtual MAC address. Consequently, the standby router cannot take over if the active fails, which is exactly the redundancy failure observed.
✗R2 has a lower HSRP priority than R1, so it cannot become standby.Wrong answer — click to see why▾
Why this is wrong here
The output shows R2 is Active in its own group (20); priority only affects role election within the same group. The real problem is separate group numbers.
✗The HSRP authentication strings do not match.Wrong answer — click to see why▾
Why this is wrong here
With mismatched authentication, the state would not be Active. The exhibit clearly shows Active on both routers, so authentication is not the cause.
✗HSRP version 1 is used on R1 while version 2 is used on R2.Wrong answer — click to see why▾
Why this is wrong here
Version mismatch would not change the displayed group number; the group number discrepancy is the direct evidence shown in the exhibit.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
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Key term
Default gateway
A default gateway is a network device, typically a router, that acts as the exit point for traffic from a local network to other networks, including the internet.
Key term
Failover
Failover is the automatic switching to a backup system when the primary system fails, ensuring continuous operation and minimal downtime.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.