The correct answer is that this configuration sets the administrative distance to 150 for all EIGRP routes learned from any neighbor whose source IP address falls within the 10.0.0.0/8 range. The `distance` command in EIGRP, when paired with a wildcard mask (acting as an implicit access-list), overrides the default AD of 90 or 170 on a per-source basis, meaning only routes originating from a router with an interface IP matching 10.x.x.x will be assigned the lower trustworthiness of 150. On the Cisco CCNP ENARSI 300-410 exam, this tests your understanding of how EIGRP distance can be manipulated per neighbor rather than globally, a common trap being that students confuse this with filtering routes or setting a metric. Remember the key distinction: the wildcard mask here matches the *source IP* of the routing update, not the network prefix being advertised. A useful memory tip is "source, not route"—the distance command with a mask always targets where the update came from, not what it carries.
300-410 Administrative Distance Practice Question
This 300-410 practice question tests your understanding of administrative distance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A network engineer configures the following on a router:
```
router eigrp 100
distance 150 10.0.0.0 0.255.255.255
```
What is the intended effect?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It sets the administrative distance to 150 for routes learned from any neighbor whose source IP matches the wildcard mask 0.255.255.255.
The `distance` command with an access-list qualifier sets AD for routes matching the ACL. Here, routes from the 10.0.0.0/8 range will have AD 150.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
It sets the administrative distance for all EIGRP routes to 150.
It sets the administrative distance to 150 for all routes in the routing table with destination 10.0.0.0/8.
Why it's wrong here
The ACL matches the source IP of the route, not the destination.
✗
It sets the administrative distance to 150 for EIGRP external routes only.
Why it's wrong here
No such distinction is made.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
Administrative Distance — This question tests Administrative Distance — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: It sets the administrative distance to 150 for routes learned from any neighbor whose source IP matches the wildcard mask 0.255.255.255. — The `distance` command with an access-list qualifier sets AD for routes matching the ACL. Here, routes from the 10.0.0.0/8 range will have AD 150.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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