MTU

Definitions

1. Maximum Transmission Unit — the largest packet size (in bytes) that a network link can transmit without fragmentation. Standard Ethernet MTU is 1500 bytes. Mismatched MTU settings between network segments cause mysterious failures where small requests work fine but large transfers fail, a notoriously tricky debugging scenario.

   In plain English: The maximum size of a data package a network can handle in one go — if it's set wrong, big transfers mysteriously break while small ones work fine.

   Example: The VPN tunnel worked for API calls but file uploads over 1400 bytes would silently fail — classic MTU issue from the IPsec overhead.

Related Terms

• ICMP
• packet
• traceroute