- A
90
Internal EIGRP routes have a default AD of 90.
- B
110
Why wrong: 110 is the default AD for OSPF.
- C
120
Why wrong: 120 is the default AD for RIP.
- D
170
Why wrong: 170 is the default AD for external EIGRP routes.
Question 2,002 of 2,152
EIGRP Default AD Value
This 300-410 practice question tests your understanding of eigrp troubleshooting. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
What is the default administrative distance for internal EIGRP routes?
Quick Answer
The answer is 90, as Cisco IOS assigns a default administrative distance of 90 to internal EIGRP routes. This value reflects EIGRP’s high reliability as an advanced distance-vector protocol, using features like Diffusing Update Algorithm (DUAL) and feasible successors to ensure loop-free, fast convergence, which justifies a lower AD than external routes. On the Cisco CCNP ENARSI 300-410 exam, this distinction is frequently tested in questions about route selection or redistribution, often paired with the trap that external EIGRP routes use 170—a common point of confusion. Remember that internal EIGRP routes are learned from within the same autonomous system, so they are inherently more trustworthy than redistributed external routes. A simple memory tip: internal EIGRP is “90 degrees” of trust, while external EIGRP is “170 degrees” of caution.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
90
The default administrative distance for internal Enhanced Interior Gateway Routing Protocol (EIGRP) routes is 90. This value is used by Cisco routers to select the best path when multiple routing protocols provide route information for the same destination network, with a lower administrative distance being preferred over a higher one.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
90
- ✗
110
- ✗
120
- ✗
170
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between internal and external EIGRP administrative distances, so the trap here is that candidates may confuse the default AD of 170 for external EIGRP routes with the AD of 90 for internal EIGRP routes.
Detailed technical explanation
How to think about this question
EIGRP uses a composite metric based on bandwidth, delay, load, and reliability to calculate the best path, but the administrative distance (AD) is a separate trustworthiness value used when comparing routes from different sources. Internal EIGRP routes have an AD of 90, while external EIGRP routes (those learned via redistribution) have an AD of 170, ensuring that internal routes are always preferred over external ones. In a real-world scenario, if a router learns a route to 10.0.0.0/8 via both OSPF (AD 110) and internal EIGRP (AD 90), the EIGRP route will be installed in the routing table because of its lower AD.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
What to study next
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FAQ
Questions learners often ask
What does this 300-410 question test?
EIGRP Troubleshooting — This question tests EIGRP Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 90 — The default administrative distance for internal Enhanced Interior Gateway Routing Protocol (EIGRP) routes is 90. This value is used by Cisco routers to select the best path when multiple routing protocols provide route information for the same destination network, with a lower administrative distance being preferred over a higher one.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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