N10-009 - Network Implementation (20% of the exam) - Section 2.2

Compare and contrast routing technologies and bandwidth management concepts, including static and dynamic routing protocols and traffic prioritisation.

Compare static routing with dynamic routing protocols - OSPF, EIGRP, and BGP - and explain how administrative distance and metrics select the best path to a destination. Apply bandwidth-management concepts such as traffic shaping and quality of service (QoS) to prioritise latency-sensitive traffic, and recognise when NAT and default routes are appropriate.

Static vs dynamic routingOSPF and BGPAdministrative distanceQuality of Service

Practice question for this objective

Free sampleNetwork Implementationhard

A border router learns the prefix 203.0.113.0/24 from an external BGP neighbour (administrative distance 20) and from OSPF (administrative distance 110). An administrator expected the internal OSPF path to be used but finds traffic following the BGP-learned path. Which explanation is correct?

AThe router installs the eBGP route because its administrative distance of 20 is lower than OSPF's 110, so it is treated as more trustworthy. Correct
BThe router installs the eBGP route because BGP overrides interior gateway protocols independent of any administrative distance value.
CThe router installs the eBGP route because path-vector protocols carry a better metric than link-state protocols do.
DThe router installs the eBGP route because OSPF external routes are assigned an administrative distance of 254.

External BGP's administrative distance of 20 is lower than OSPF's 110, so eBGP routes are installed over OSPF for the same prefix. Route-source selection compares administrative distance before any metric; external BGP's default distance of 20 is lower than OSPF's 110, so the router trusts and installs the eBGP path rather than the OSPF one.

Why A is correct: External BGP carries an administrative distance of 20, which is lower than OSPF's 110; the router therefore treats the eBGP source as more trustworthy and installs that route over the OSPF one.

Why B is wrong: BGP does not override interior gateway protocols by a special rule; selection is by administrative distance, and internal BGP at 200 would in fact lose to OSPF, so this reasoning is incorrect.

Why C is wrong: Metrics such as BGP path attributes and OSPF cost are never compared across different protocols; only administrative distance decides between sources, so a metric-based explanation is wrong.

Why D is wrong: OSPF external routes keep an administrative distance of 110 by default, not 254; 254 is not the OSPF external value, so this explanation rests on a fabricated distance.

See more N10-009 practice questions, answers explained.

Exam traps in Network Implementation

Answers that look right on this material and are not. Each one is a distractor from a different question in the N10-009 bank for this domain.

Add more specific static routes for every alternate path so a backup entry already exists for each destination in advance.
Why it is wrong: Pre-loading alternate static routes multiplies the manual maintenance the team is already struggling with and still cannot detect a remote link failure to switch paths automatically.
The internal BGP route, because BGP-sourced prefixes take precedence over interior gateway protocols like OSPF.
Why it is wrong: Only external BGP at 20 outranks OSPF; internal BGP sits at 200 and therefore loses to OSPF at 110, so a blanket claim that BGP outranks interior gateway protocols is wrong.
The OSPF route, because a dynamically learned path automatically supersedes any manually configured route, regardless of administrative distance value.
Why it is wrong: It is tempting to assume a dynamic protocol is always fresher and therefore wins, but administrative distance exists precisely to rank sources, and the lower static value is preferred over OSPF.

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