CCNA IP 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.

• ✓

  1. Perform longest prefix match on the destination IP address against all routes in the routing table. 2. If multiple routes match, compare administrative distances; choose the route with the lowest AD. 3. If multiple routes have the same AD, compare metrics; choose the route with the lowest metric. 4. Forward the packet using the selected route.

  Why this is correct

  This is correct because it follows the exact order of the router's decision process: longest prefix match first to narrow down candidate routes, then administrative distance to select the most trusted source, then metric to choose the best path among equal-AD routes, and finally forwarding.

• ✗

  1. Compare administrative distances of all routes; choose the route with the lowest AD. 2. Perform longest prefix match on the destination IP address against the remaining routes. 3. If multiple routes have the same AD, compare metrics; choose the route with the lowest metric. 4. Forward the packet using the selected route.

  Why it's wrong here

  This ordering is wrong because administrative distance (AD) is not a measure of route specificity; it is a measure of the trustworthiness of the routing source. The router's first decision criterion is always the longest prefix match, because the packet must be forwarded along the most specific network path. If you compare AD first, a static default route (AD 1) would incorrectly outrank a more specific OSPF route (AD 110) even though the OSPF route's longer prefix makes it the only correct candidate. Only after the longest prefix match has isolated the candidate set should AD be used to pick the most trusted protocol among those candidates.

• ✗

  1. Perform longest prefix match on the destination IP address against all routes in the routing table. 2. If multiple routes match, compare metrics; choose the route with the lowest metric. 3. If multiple routes have the same metric, compare administrative distances; choose the route with the lowest AD. 4. Forward the packet using the selected route.

  Why it's wrong here

  This is incorrect because metric is compared only after administrative distance. AD is used to select the best source of routing information; metric is only relevant when comparing routes from the same source (same AD).

• ✗

  1. Compare metrics of all routes; choose the route with the lowest metric. 2. Perform longest prefix match on the destination IP address against the remaining routes. 3. If multiple routes have the same metric, compare administrative distances; choose the route with the lowest AD. 4. Forward the packet using the selected route.

  Why it's wrong here

  This sequence is invalid because metric values are only comparable among routes from the same routing protocol (same AD); comparing metrics first would force meaningless comparisons, such as an OSPF cost of 20 against an EIGRP metric of 28416. Additionally, the longest prefix match is the primary determinant of the forwarding decision, and AD must be evaluated before metric because AD selects which routing source's routes are eligible. Starting with metric also ignores the fact that routers first narrow routes by mask length, then by source trust, and only then by path cost within that source. Thus, this ordering inverts the functional hierarchy and would produce incorrect path selection.

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?”