O 10.10.50.0/24 [110/20] via 192.168.12.2, GigabitEthernet0/0 D 10.10.50.0/24 [90/30720] via 192.168.13.2, GigabitEthernet0/1
A router shows the following routing table entries for the same destination:
O 10.10.50.0/24 [110/20] via 192.168.12.2, GigabitEthernet0/0 D 10.10.50.0/24 [90/30720] via 192.168.13.2, GigabitEthernet0/1
Which route will become the active route in the routing table?
Answer choices
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
The OSPF route, because its metric is lower
This is the classic wrong answer because the OSPF metric looks smaller. The mistake is treating metric values from different protocols as if they mean the same thing. They do not. The router first compares administrative distance when choosing between route sources such as OSPF and EIGRP, and only then uses metrics within a single protocol's own logic.
The EIGRP route, because its administrative distance is lower
Correct. This is correct. EIGRP wins here because its default administrative distance of 90 is lower than OSPF's 110, so the router trusts the EIGRP route more when both advertise the same destination prefix.
Both routes, because the prefixes are identical
Routers do not automatically install both routes just because the prefix is identical. When the entries come from different routing protocols, the router chooses the source with the best administrative distance first. Only after that, and usually within the same protocol, do equal-cost load-balancing rules come into play.
Neither route, because the metrics use different scales
It is true that the metrics use different scales, but that does not mean the router rejects both routes. Cisco routers solve that comparison problem by using administrative distance first. In this case they still choose one route, and it is the EIGRP route.
Common exam trap
A common exam trap is to assume the route with the numerically lower metric value is preferred regardless of the routing protocol. Candidates often compare OSPF’s metric of 20 directly to EIGRP’s metric of 30720 and mistakenly choose the OSPF route. This is incorrect because metrics from different protocols are not comparable. The router first compares administrative distance values, which represent trustworthiness, before metrics. Ignoring administrative distance leads to wrong conclusions about which route becomes active.
Technical deep dive
Administrative distance (AD) is a fundamental concept in Cisco routing that determines the trustworthiness of routing information sources. Each routing protocol is assigned a default AD value, which the router uses to select the best path when multiple protocols advertise the same destination. Lower AD values indicate more reliable sources. For example, EIGRP internal routes have an AD of 90, while OSPF routes have an AD of 110. This means EIGRP routes are preferred over OSPF routes when both exist for the same prefix. When a router receives multiple routes to the same destination from different protocols, it first compares their administrative distances. The route with the lowest AD is installed in the routing table as the active route. Only when routes come from the same protocol does the router compare metrics to select the best path. Metrics are protocol-specific and calculated differently; OSPF uses cost based on bandwidth, while EIGRP uses a composite metric including bandwidth and delay. Because these metrics are not comparable across protocols, the router relies on AD to make the initial selection. The exam trap arises when candidates incorrectly compare metrics from different protocols directly, assuming the numerically smaller metric wins. This mistake overlooks the role of administrative distance in cross-protocol route selection. Practically, Cisco routers never compare OSPF and EIGRP metrics directly. Instead, they trust the route with the lower AD, which is why the EIGRP route with AD 90 is preferred over the OSPF route with AD 110, regardless of metric values. Understanding this behavior is essential for accurate routing table interpretation and CCNA exam success.
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise IPv4 subnetting, CIDR, masks, host ranges and subnet selection.
Practise OSPF neighbours, router IDs, metrics, areas and routing-table interpretation.
Practise VLANs, access ports, trunks, allowed VLANs and switching scenarios.
Practise spanning tree, root bridge election, port roles and STP troubleshooting.
Practise LACP, PAgP, port-channel behaviour and bundle requirements.
Practise standard and extended ACLs, permit/deny logic and traffic filtering.
Practise static NAT, dynamic NAT, PAT and inside/outside address translation.
Practise DHCP scopes, relay, leases and troubleshooting.
Practise routing-table output, longest-prefix match, AD and route selection.
Practise trunk verification and VLAN forwarding across switches.
Practise WLAN security, authentication and wireless architecture concepts.
Practise IPv6 addressing, routes, neighbour discovery and common IPv6 exam traps.
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
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FAQ
Cisco routers select the active route based on administrative distance when multiple routing protocols advertise the same destination prefix.
The correct answer is: The EIGRP route, because its administrative distance is lower — The EIGRP route becomes active because the router compares administrative distance first when the same destination is learned from different routing protocols. This is one of the most common Cisco exam traps: candidates compare the OSPF metric value of 20 to the EIGRP metric value and assume the smaller number must win. That is not how route selection works across different protocols. OSPF metrics and EIGRP metrics are calculated differently, so the router does not compare them directly. Instead it checks administrative distance. EIGRP internal routes default to 90, while OSPF routes default to 110. Since 90 is lower than 110, the EIGRP route is trusted more and is installed as the active path.
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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