Reading & Troubleshooting Routes

Covers Lesson 1 and Lesson 2

Checks that you can read a live routing table field by field, and turn it into the first tool for isolating a forwarding fault.

Topics covered

• Every field in a route line
• Connected versus local routes
• The default route and what beats it
• One-way connectivity, blackholes, and recursive-lookup failures

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 5 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.

Section quiz

Reading & Troubleshooting Routes

8 questions covering Lesson 1 and Lesson 2. Answer each one before you see whether you were right.

Question 1 of 8

1. In the route line entry [110/30], what do the two numbers represent?

2. Why does an up/up addressed interface produce both a C route and an L /32 route?

3. A table holds S 10.1.8.0/24 [1/0] and O 10.1.8.0/26 [110/30]. Which line forwards a packet to 10.1.8.5, and does the static route's lower AD matter?

4. Using that same table, which line forwards a packet to 10.1.8.70 if a default route also exists?

5. What does the line 'Gateway of last resort is not set' tell you?

6. Connectivity works from A to B but never back from B to A. What is the most likely cause, and where do you look?

7. A route is present in show ip route, but traffic is dropped two hops downstream. Which command localises the break, and what does the last responding hop tell you?

8. What is the difference in the routing table between a recursive-lookup failure and a route pointing at a next hop with no onward path?

Back to Lesson 2 Continue to Lesson 3

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