ICND1 Routing Technologies & Protocols 4 — Questions and Answers
Question 1: Which of the following best describes a classless routing protocol?
- It groups routes by class A, B, or C
- It includes subnet mask information in routing updates (Correct answer)
- It only supports summarization at class boundaries
- It does not support VLSM
Correct answer: It includes subnet mask information in routing updates
Classless routing protocols include subnet mask (prefix length) in their updates, allowing support for VLSM and CIDR.
Question 2: A router running OSPF shows a neighbor in 'EXSTART' state for an extended time. What is the most likely cause?
- Hello and dead timers are mismatched
- MTU mismatch between the two routers (Correct answer)
- OSPF process IDs are different
- Area IDs are mismatched
Correct answer: MTU mismatch between the two routers
An MTU mismatch prevents OSPF routers from successfully exchanging DBD packets, causing the neighbor to stall in EXSTART/EXCHANGE state.
Question 3: What is the administrative distance of an EIGRP internal route?
- 90 (Correct answer)
- 110
- 100
- 120
Correct answer: 90
EIGRP internal routes have an administrative distance of 90, making them preferred over OSPF (110) and RIP (120).
Question 4: Which statement about RIPv2 is true?
- It uses multicast address 224.0.0.9 for updates (Correct answer)
- It supports a maximum hop count of 16
- It uses unicast to send routing updates
- It does not support authentication
Correct answer: It uses multicast address 224.0.0.9 for updates
RIPv2 sends routing updates to the multicast address 224.0.0.9, unlike RIPv1 which used broadcast.
Question 5: A Cisco router has the following routes: S 10.0.0.0/8, O 10.1.0.0/16, and C 10.1.1.0/24. Which route is selected for a packet destined to 10.1.1.50?
- S 10.0.0.0/8 because static routes are preferred
- O 10.1.0.0/16 because OSPF has a lower AD than static
- C 10.1.1.0/24 because it is the longest prefix match (Correct answer)
- O 10.1.0.0/16 because it has the longest match among dynamic routes
Correct answer: C 10.1.1.0/24 because it is the longest prefix match
Longest prefix match is always the primary selection criterion; 10.1.1.0/24 is the most specific match for 10.1.1.50.
Question 6: Which OSPF LSA type describes routes external to the OSPF domain?
- Type 1 (Router LSA)
- Type 2 (Network LSA)
- Type 3 (Summary LSA)
- Type 5 (AS External LSA) (Correct answer)
Correct answer: Type 5 (AS External LSA)
Type 5 LSAs are generated by ASBR routers to advertise routes redistributed from external routing domains into OSPF.
Question 7: What happens when a RIP router receives a route update advertising a destination with a hop count of 16?
- It installs the route with metric 16
- It treats the destination as unreachable and discards the route (Correct answer)
- It resets the hop count to 15 before installing
- It requests an alternative path via a query message
Correct answer: It treats the destination as unreachable and discards the route
In RIP, a hop count of 16 represents infinity, meaning the destination is unreachable and the route is not installed.
ICND1 Routing Technologies & Protocols 4
Which of the following best describes a classless routing protocol?