CCNA Longest prefix match in routing Practice Question

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 static route to 10.60.4.16/28

  Why this is correct

  The destination address 10.60.4.17 falls within all three advertised prefixes, but the router selects the route with the longest prefix match. The static route to 10.60.4.16/28 uses a 28-bit subnet mask, which is longer than the 24-bit OSPF route and the 16-bit EIGRP route. Because this /28 prefix provides the most specific match for the destination, it overrides the other less-specific entries in the routing table.

• ✗

  The OSPF route to 10.60.4.0/24

  Why it's wrong here

  The OSPF route to 10.60.4.0/24 is not selected because the packet’s destination 10.60.4.17 falls within the 10.60.4.16/28 static route, which offers a longer prefix length (28 bits) and therefore a more specific match, overriding the OSPF route’s 24-bit prefix. This option is tempting because OSPF is a dynamic, link-state protocol commonly used for internal routing, and the 10.60.4.0/24 subnet does encompass 10.60.4.17; it would be correct if no static route with a longer prefix existed for that destination.

  When this WOULD be correct

  If the question asked which route would be used for a destination within the 10.60.4.0/24 subnet without a more specific static route, then the OSPF route to 10.60.4.0/24 would be the correct answer, as it would be the best match for any address in that range.

• ✗

  The EIGRP route to 10.60.0.0/16

  Why it's wrong here

  The EIGRP route to 10.60.0.0/16 is indeed a valid match for the destination 10.60.4.17, as the /16 mask encompasses this address. However, the router's tie-breaker for overlapping routes is the longest prefix length, not administrative distance or metric. With only 16 bits of subnet mask, this route is the least specific of the three candidates, so it is never chosen when a longer-prefix route like the /28 static route exists for the same destination.

  When this WOULD be correct

  If the question asked which route would be used if the static route to 10.60.4.16/28 were removed, then the EIGRP route to 10.60.0.0/16 would be the correct answer, as it would be the next best match for the destination.

• ✗

  No route at all

  Why it's wrong here

  The device cannot discard the packet as 'no route' because the routing table in the exhibit contains multiple entries whose subnet masks include the destination 10.60.4.17. Forwarding decisions are based on longest prefix match, and the presence of the 10.60.4.16/28 static route guarantees that a valid next hop exists. A 'no route' condition would occur only if the destination did not match any prefix in the routing table, which is clearly not the case here.

  When this WOULD be correct

  In a scenario where the routing table has been cleared or all routes have been removed, a question could ask if there are any routes available for destination 10.60.4.17. In this case, the correct answer would be 'No route at all' as there would be no valid paths to the destination.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”