350-501 Question #56: Real Exam Question with Answer & Explanation

The correct answer is B: 4 bytes. When configuring 802.1q VLAN tagging, the MTU must be increased by 4 bytes to accommodate the Tag Protocol Identifier (TPID) and Tag Control Information (TCI) fields added to the Ethernet frame.

Networking

Question

How much must the MTU be increased when configuring the 802.1q VLAN tag?

Options

A2 bytes
B4 bytes
C8 bytes
D12 bytes

Explanation

When configuring 802.1q VLAN tagging, the MTU must be increased by 4 bytes to accommodate the Tag Protocol Identifier (TPID) and Tag Control Information (TCI) fields added to the Ethernet frame.

Common mistakes.

A. A 2-byte increase would only account for either the TPID or TCI, not the full 802.1Q tag.
C. An 8-byte increase is more than double the required size for a standard 802.1Q tag.
D. A 12-byte increase is significantly more than the size of a standard 802.1Q tag.

Concept tested. 802.1Q VLAN tag size

Reference. https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/multiboot/configuration_guide/b_multiboot_3se_cg/b_multiboot_3se_cg_chapter_0110.html

Topics

#802.1q#VLAN tagging#MTU#Ethernet frame

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