Cisco Certified Network Professional Practice Test 2026 – Your All-in-One Guide to Exam Success!

The maximum MTU size for frames using 802.1Q is 1522 bytes. This standard defines a method for encapsulating VLAN tags within Ethernet frames. Originally, standard Ethernet frames had a maximum size of 1518 bytes, which includes the payload and various headers, but does not account for the extra bytes added by an Ethernet tag.

When VLAN tagging is used (as defined by 802.1Q), an additional 4 bytes are added to the frame to accommodate the VLAN tag. This increases the maximum frame size to 1522 bytes. Therefore, when configuring network devices that utilize VLANs, it's important to account for this additional size to avoid fragmentation and ensure optimal performance across the network.

Overall, understanding the implications of the MTU size in relation to VLANs is crucial for network design and troubleshooting in a Cisco environment.