Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Which statement best describes the purpose of administrative distance when two different routing sources advertise the same prefix?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
It ranks the trustworthiness of different route sources advertising the same destination.
This is correct because administrative distance is a source-preference value.
B
Distractor review
It determines the MAC address of the next hop.
This is wrong because MAC resolution is not the purpose of administrative distance.
C
Distractor review
It specifies the native VLAN for trunk links.
This is wrong because administrative distance is unrelated to VLAN trunking.
D
Distractor review
It defines the subnet mask of the learned route.
This is wrong because prefix length is part of the route itself, not the administrative-distance function.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is mistaking administrative distance for routing metrics or other unrelated concepts like VLAN configuration or MAC address resolution. Candidates often confuse AD with the metric used inside routing protocols to select the best path among multiple routes from the same protocol. However, administrative distance operates at a higher decision level, comparing route sources rather than path costs. Selecting answers that describe subnet masks, VLANs, or MAC addresses as AD functions is incorrect because AD only ranks the trustworthiness of routing sources, not Layer 2 or subnetting details.
Technical deep dive
How to think about this question
Administrative distance is a numerical value assigned by Cisco routers to rate the reliability or trustworthiness of routing information received from different routing protocols or sources. It acts as a preference ranking system that helps the router decide which route to install in its routing table when multiple routes to the same destination prefix exist from different routing sources. Each routing protocol has a default administrative distance; for example, directly connected interfaces have an AD of 0, static routes 1, EIGRP 90, OSPF 110, and RIP 120. The lower the AD, the more preferred the route source. When a router receives multiple advertisements for the same network prefix from different routing protocols, it compares their administrative distances first. The route with the lowest AD is selected and installed in the routing table, regardless of the metric values used within each protocol. This selection process ensures that the router trusts the most reliable source before considering path cost or metric. If two routes have the same AD, the router then compares the metrics within the routing protocol to select the best path. A common exam trap is confusing administrative distance with routing metrics or other network concepts like VLANs or MAC address resolution. Administrative distance is strictly about source trustworthiness, not path cost or Layer 2 addressing. Practically, understanding AD is crucial in multi-protocol environments where static routes, EIGRP, OSPF, or other protocols coexist. Misunderstanding AD can lead to unexpected routing behavior, such as a less optimal route being installed or routing loops if the router trusts an unintended source.
KKey Concepts to Remember
- Administrative distance (AD) determines the trustworthiness of routing information sources when multiple protocols advertise the same destination prefix.
- Routers use administrative distance to select the best route among different routing protocols before considering metrics within a single protocol.
- A lower administrative distance value indicates a more preferred and trusted route source by the router.
- Static routes typically have a lower administrative distance than dynamic routing protocols, making them more preferred if both advertise the same prefix.
- Administrative distance is a router-internal value and does not affect the actual routing metric or path cost used within routing protocols like OSPF or EIGRP.
- When two routes to the same destination have equal administrative distance, the router uses the routing protocol metric to choose the best path.
- Administrative distance does not influence MAC address resolution, VLAN configuration, or subnet mask determination.
- Understanding administrative distance helps prevent routing conflicts and ensures predictable routing behavior in multi-protocol environments.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
Administrative distance (AD) determines the trustworthiness of routing information sources when multiple protocols advertise the same destination prefix.
What is the correct answer to this question?
The correct answer is: It ranks the trustworthiness of different route sources advertising the same destination. — Administrative distance helps the router decide which route source to trust more. In plain language, if the same network is learned from two different sources, such as OSPF and a static route, the router needs a source-preference rule before it can install one. Administrative distance provides that rule. This is different from a metric, which typically compares multiple paths inside the same routing protocol. The correct answer is the one focused on source trust rather than path cost inside one protocol.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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