Courseiva
← 300-410
Full test
Question 30 of 2,152
Route Summarization →hardMultiple ChoiceObjective-mapped

Quick Answer

The root cause is that the summary route 192.168.0.0/22 configured on R1 does not include the 192.168.10.0/24 subnet, so the specific route is suppressed and never advertised to R2. This happens because EIGRP’s automatic summarization behavior, when a manual summary is configured, blocks any more specific routes that fall outside the summary range—in this case, 192.168.0.0/22 covers only 192.168.0.0 through 192.168.3.255, leaving 192.168.10.0/24 entirely excluded. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how manual route summarization interacts with the routing table; a common trap is assuming a summary route automatically includes all subnets of the same major network, when in fact the summary prefix must explicitly cover the missing subnet. To remember this, think of the summary as a net: if the subnet’s address is outside the net’s boundaries, it slips through and is lost.

300-410 Route Summarization Practice Question

This 300-410 practice question tests your understanding of route summarization. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

A large enterprise network is experiencing intermittent reachability to a specific /24 subnet (192.168.10.0/24) from remote sites. Router R1 has the following relevant configuration:

interface GigabitEthernet0/0
 ip address 10.0.1.1 255.255.255.0

!

router eigrp 100
 network 10.0.0.0
 network 192.168.0.0

!

interface GigabitEthernet0/1
 ip address 192.168.1.1 255.255.255.0
 ip summary-address eigrp 100 192.168.0.0 255.255.252.0

!

Router R2 shows:
R2# show ip route 192.168.10.0

Routing entry for 192.168.0.0/22, supernet Known via "eigrp 100", distance 90, metric 30720, type internal Last update from 10.0.1.1 on GigabitEthernet0/0, 00:00:15 ago

* 10.0.1.1, via GigabitEthernet0/0, 00:00:15 ago

What is the root cause?

Question 1hardmultiple choice
Study the full EIGRP explanation →

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 summary route 192.168.0.0/22 does not include 192.168.10.0/24, so the specific route is not advertised and is missing from R2's routing table.

The summary route 192.168.0.0/22 is being advertised by R1, but it blocks the more specific /24 route 192.168.10.0/24 if that subnet is not within the summary range (192.168.0.0/22 covers 192.168.0.0 to 192.168.3.255). Since 192.168.10.0/24 is outside this range, it is not summarized and is not advertised separately, causing reachability failure. The correct fix is to adjust the summary prefix to include the missing subnet, or to not summarize.

Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✓

    The summary route 192.168.0.0/22 does not include 192.168.10.0/24, so the specific route is not advertised and is missing from R2's routing table.

    Why this is correct

    The summary covers only 192.168.0.0-192.168.3.255, excluding 192.168.10.0/24.

    Related concept

    CIDR notation defines the prefix length.

  • ✗

    EIGRP has a metric mismatch between the summary and the specific route, causing the specific route to be suppressed.

    Why it's wrong here

    EIGRP does not suppress specific routes due to metric mismatch; the summary is simply not covering the subnet.

  • ✗

    The network command for 192.168.0.0 is missing, causing EIGRP to not advertise any 192.168.x.x routes.

    Why it's wrong here

    The network command includes 192.168.0.0, so routes are advertised.

  • ✗

    R2 has a static route for 192.168.10.0/24 that is overriding the EIGRP route.

    Why it's wrong here

    No static route is shown; the issue is with the summary.

Common exam traps

Common exam trap: usable hosts are not the same as total addresses

Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.

Trap categories for this question

  • Command / output trap

    The network command includes 192.168.0.0, so routes are advertised.

Detailed technical explanation

How to think about this question

Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.

KKey Concepts to Remember

  • CIDR notation defines the prefix length.
  • Block size helps identify subnet boundaries.
  • Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
  • The required host count determines the smallest suitable subnet.

TExam Day Tips

  • Write the block size before choosing the subnet.
  • Check whether the question asks for hosts, subnets or a specific address range.
  • Do not confuse /24, /25, /26 and /27 host counts.

Key takeaway

Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

Real-world example

How this comes up in practice

A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.

What to study next

Got this wrong? Here's your next step.

Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.

Related practice questions

Related 300-410 practice-question pages

Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

Layer 3 Technologies practice questions

Practise 300-410 questions linked to Layer 3 Technologies.

EIGRP Troubleshooting practice questions

Practise 300-410 questions linked to EIGRP Troubleshooting.

OSPF Troubleshooting (v2/v3) practice questions

Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).

BGP Troubleshooting practice questions

Practise 300-410 questions linked to BGP Troubleshooting.

Route Redistribution practice questions

Practise 300-410 questions linked to Route Redistribution.

Policy-Based Routing (PBR) practice questions

Practise 300-410 questions linked to Policy-Based Routing (PBR).

VRF-Lite practice questions

Practise 300-410 questions linked to VRF-Lite.

Route Maps and Route Filtering practice questions

Practise 300-410 questions linked to Route Maps and Route Filtering.

Administrative Distance practice questions

Practise 300-410 questions linked to Administrative Distance.

Route Summarization practice questions

Practise 300-410 questions linked to Route Summarization.

Bidirectional Forwarding Detection (BFD) practice questions

Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).

VPN Technologies practice questions

Practise 300-410 questions linked to VPN Technologies.

Practice this exam

Start a free 300-410 practice session

Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.

10 questions20 questions30 questions50 questionsTimed 30
300-410 practice-test guide →Study guide →Browse all practice tests

FAQ

Questions learners often ask

What does this 300-410 question test?

Route Summarization — This question tests Route Summarization — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The summary route 192.168.0.0/22 does not include 192.168.10.0/24, so the specific route is not advertised and is missing from R2's routing table. — The summary route 192.168.0.0/22 is being advertised by R1, but it blocks the more specific /24 route 192.168.10.0/24 if that subnet is not within the summary range (192.168.0.0/22 covers 192.168.0.0 to 192.168.3.255). Since 192.168.10.0/24 is outside this range, it is not summarized and is not advertised separately, causing reachability failure. The correct fix is to adjust the summary prefix to include the missing subnet, or to not summarize.

What should I do if I get this 300-410 question wrong?

Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.

What is the key concept behind this question?

CIDR notation defines the prefix length.

About these practice questions

Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →

How Courseiva writes practice questions · Editorial policy

Same concept, more angles

1 more ways this is tested on 300-410

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A network engineer is troubleshooting an EIGRP network where route summarization is configured. Router R1 has the 'ip summary-address eigrp 100 10.0.0.0 255.0.0.0' command on its interface facing R2. After the configuration, R2 loses connectivity to the 10.1.0.0/16 subnet, which is one of the component routes. The engineer checks the routing table on R2 and sees the summary route 10.0.0.0/8 but not the specific route. What is the most likely cause?

medium
  • A.The summary route 10.0.0.0/8 is being advertised with a metric of infinity, causing it to be ignored.
  • B.The 10.1.0.0/16 subnet is not directly connected to R1, so it cannot be summarized.
  • C.The summary address command was applied on the wrong interface, causing the summary to be sent out all interfaces, including the one facing the 10.1.0.0/16 subnet's origin.
  • ✓ D.The 10.1.0.0/16 subnet is not included in the summary range because the summary mask is /8, but the subnet's network address is 10.1.0.0, which is within the range, but the EIGRP process may have a split-horizon issue or the component route is not in the EIGRP topology table.

Why D: In EIGRP, the summary address command suppresses the advertisement of more specific routes and generates the summary. However, if the summary route is not installed in the routing table (e.g., due to a missing component), the specific routes may still be suppressed, causing a black hole.

Last reviewed: Jun 18, 2026

Question Discussion

Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.

Loading comments…

Sign in to join the discussion.

This 300-410 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 300-410 exam.