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350-401 · Question #1015
350-401 Question #1015: Real Exam Question with Answer & Explanation
The correct answer is B: interface MTU mismatch. OSPF fails to establish adjacency between R1 and R2 when there is an interface MTU mismatch, as it prevents the successful exchange of Database Description (DD) packets.
Submitted by kavita_s· Mar 6, 2026Network Assurance
Question
Refer to the exhibit. Why does OSPF fail to establish an adjacency between R1 and R2?
Options
- Aauthentication mismatch
- Binterface MTU mismatch
- Ctimers mismatch
- Darea mismatch
Explanation
OSPF fails to establish adjacency between R1 and R2 when there is an interface MTU mismatch, as it prevents the successful exchange of Database Description (DD) packets.
Common mistakes.
- A. An authentication mismatch would prevent adjacency formation, but the question specifically points to MTU as the correct reason, implying the exhibit showed no authentication issues.
- C. A timers mismatch (hello or dead intervals) would prevent adjacency formation, but the question specifically points to MTU as the correct reason, implying the exhibit showed no timer issues.
- D. An area mismatch would prevent adjacency formation between routers that are meant to be in the same area, but the question specifically points to MTU as the correct reason, implying the exhibit showed no area ID issues.
Concept tested. OSPF MTU mismatch preventing adjacency
Reference. https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13689-18.html
Topics
#OSPF adjacency#MTU mismatch#Network troubleshooting
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