Week 4 Checkpoint

Covers all five Week 4 lessons

Confirms the week's five lessons form one skill: predicting exactly which route a router installs and uses. Route selection is the spine here, applied across everything the week built.

Topics covered

• The forwarding loop and the routing table's sources
• Static, default, and floating routes in combination
• Longest-prefix match, administrative distance, and metric in order
• Diagnosing a path that is not the one you expected

Every question here is answerable from the first-party notes of the lessons above. You commit to an answer before you see whether it was right.

This quiz is a Week 4 milestone in its own right. Passing it does not change the completion state of any individual lesson, and you do not need it to finish the lessons it covers.

Weekly checkpoint

Week 4 Checkpoint

12 questions covering all five Week 4 lessons. Answer each one before you see whether you were right.

Question 1 of 12

1. State the order in which a router applies its three route-selection tests.

2. A table has O 10.1.0.0/16 [110/20] and S 10.1.1.0/24 [1/0]. Which carries a packet to 10.1.1.50, and which test decided it?

3. A router has a /26 connected route (AD 0) and a /24 static route (AD 1) covering a destination in the /26 range. It also has a /16 OSPF route with an excellent metric. Which wins?

4. Both OSPF and a static route describe the identical prefix 10.1.5.0/24. Which installs, and why?

5. When does a router compare metrics?

6. A router has two up/up interfaces, one addressed /24 and one /30, and no configured routes. How many entries are in its routing table?

7. A static route recurses through a next hop that lives on a connected subnet. The transit interface is shut down. What does show ip route show for the static route, and why?

8. R1 — R2 — R3 in a line, each end router with a LAN, two /30 transit links. What is the minimum number of static routes needed for a successful ping between the two LANs?

9. A router has a default route and specific routes for several internal subnets. Traffic to an internal subnet suddenly starts leaving via the default. What changed?

10. An engineer configures a floating static, cannot find it in show ip route, and re-enters the command twice. What should they have done?

11. OSPF is fully adjacent and advertising 10.1.5.0/24, but traffic takes an old link instead. show ip route 10.1.5.20 reports Known via static. What is the fix if OSPF should own the prefix?

12. show ip route <destination> returns a valid matching entry, yet the ping still fails. Which two things should you check next?

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