Exam preparation
CCNA
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4 guides for this exam — how to prepare, what to practise, and how to know it has gone in.
A written answer, marked
A question from a CCNA mock paper, answered and marked. From How to Prepare for CCNA: A Practical Study Guide.
A router has 10.20.0.0/16 and 10.20.32.0/19 routes in its table. It receives traffic for 10.20.40.12. Which route is selected, and why?
3/4The 10.20.0.0/16 route is selected because it is the larger network and covers the address. I would then forward it to that route's next hop.
You identified that both routes cover 10.20.40.12, but selected the less specific route. Route selection starts with the longest prefix match, before administrative distance or metric are considered.
Missed
−10.20.32.0/19 is more specific than 10.20.0.0/16 and is therefore selected.
−State the forwarding interface or next hop only after selecting the route.
Model answerBoth routes cover 10.20.40.12, but 10.20.32.0/19 is selected because /19 is a longer prefix than /16. The router then uses the selected route's next hop or exit interface. If several routes have the same prefix length, administrative distance and then the protocol metric become relevant.
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Guides
- How to Prepare for CCNA: A Practical Study GuideA practical CCNA preparation method covering the exam areas, subnetting, CLI practice, troubleshooting, mock papers and revision.
- CCNA Study Plan: A Practical Six-Week Revision MethodA six-week CCNA study plan with focused sessions for subnetting, routing, switching, security, automation and scenario-based questions.
- CCNA Flashcards: A Practical Deck for Network RevisionStudy a focused CCNA flashcard deck covering subnetting, routing, VLANs, security and troubleshooting with precise answers and review rules.
- CCNA Practice Questions: 10 Scenario-Based DrillsWork through 10 CCNA practice questions on subnetting, routing, switching, security, troubleshooting and automation, with explanations.
Preparing for CCNA? Build your CCNA board from your own notes — the cards, papers and lectures are written from it. Free plan: 20 cards, a paper, a lecture and a viva to try.
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