Question 1mediummatching
Full question →Match each route source to its default administrative distance on a Cisco router.
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mediummatchingObjective-mapped
Match each route source to its default administrative distance on a Cisco router.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is confusing administrative distance with routing metrics. Candidates often assume that the lowest metric route is always chosen, but Cisco routers first compare administrative distance when routes come from different sources. For example, even if an OSPF route has a better metric than a static route, the router prefers the static route because its administrative distance (1) is lower than OSPF’s (110). Misreading this can lead to incorrect answers about route preference and cause confusion in troubleshooting routing issues.
Technical deep dive
How to think about this question
Administrative distance (AD) is a fundamental concept in Cisco routing that determines the reliability of routing information received from various sources. It is a numeric value assigned to each route source, where a lower AD indicates a more trustworthy route. Cisco routers use AD to decide which route to install in the routing table when multiple routes to the same destination exist from different routing protocols or sources. The AD values are predefined but can be manually adjusted for advanced routing scenarios. The default administrative distances for common route sources are critical to understand for CCNA-level routing knowledge. Connected interfaces have an AD of 0, meaning they are always preferred since they represent directly attached networks. Static routes have an AD of 1, making them the next most trusted after connected routes. External BGP (eBGP) routes have an AD of 20, which is lower than most interior gateway protocols, so eBGP routes are preferred over OSPF (AD 110) and EIGRP external routes (AD 170). OSPF routes have an AD of 110, which is higher than static and eBGP but lower than RIP (AD 120). This hierarchy ensures predictable route selection based on trustworthiness. A common exam trap is confusing administrative distance with routing protocol metrics. While AD compares route sources, metrics determine the best path within the same routing protocol. For example, OSPF uses cost as its metric, but if a static route exists to the same destination, the router prefers the static route due to its lower AD. Misunderstanding this can lead to incorrect assumptions about route selection. Practically, network engineers use AD to manipulate route preferences and implement routing policies, such as preferring static routes over dynamic ones or controlling route redistribution.
KKey Concepts to Remember
- Administrative distance (AD) is a Cisco router metric that ranks the trustworthiness of routing information from different sources to select the best path.
- Connected routes have the lowest administrative distance of 0, so Cisco routers always prefer directly connected interfaces over other route sources.
- Static routes have an administrative distance of 1, making them more preferred than dynamic routing protocols but less preferred than connected routes.
- External BGP (eBGP) routes have an administrative distance of 20, which is lower than most interior routing protocols, so eBGP routes are preferred over OSPF and EIGRP external routes.
- OSPF routes have a default administrative distance of 110, which is higher than eBGP and static routes, so OSPF routes are less preferred when multiple routes exist.
- When multiple routes to the same destination exist, Cisco routers compare administrative distances first before considering metrics to determine the best path.
- Administrative distance is only compared between routes learned from different routing protocols or sources; routes from the same protocol use metrics for path selection.
- Understanding default administrative distances helps network engineers predict route selection behavior and troubleshoot routing issues effectively.
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) is a Cisco router metric that ranks the trustworthiness of routing information from different sources to select the best path.
What exam trap should I watch out for?
Common exam trap: answer the scenario, not the keyword: A frequent exam trap is confusing administrative distance with routing metrics. Candidates often assume that the lowest metric route is always chosen, but Cisco routers first compare administrative distance when routes come from different sources. For example, even if an OSPF route has a better metric than a static route, the router prefers the static route because its administrative distance (1) is lower than OSPF’s (110). Misreading this can lead to incorrect answers about route preference and cause confusion in troubleshooting routing issues.
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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