JNCIS-ENT: Juniper Networks Certified Specialist – Enterprise Routing and Switching (2025) — Question 3

What is the maximum allowable MTU size for a default GRE tunnel without IPv4 traffic fragmentation?

Answer options

• A. 1496 bytes
• B. 1480 bytes
• C. 1500 bytes
• D. 1476 bytes

Correct answer: D

Explanation

The correct answer is D, 1476 bytes, as this size accounts for the additional GRE header and ensures that the total packet size does not exceed the standard Ethernet MTU of 1500 bytes, preventing fragmentation. Options A, B, and C exceed this limit when the GRE encapsulation is considered, making them unsuitable for avoiding fragmentation.