MTU calculator

Stack encapsulation overheads to find the effective path MTU and the TCP MSS to clamp to.

Path

Base MTU1500 for Ethernet, 9000 for jumbo frames.
Encapsulations
Effective MTU1496
Overhead−4B
TCP MSS1456IPv4
TCP MSS1436IPv6

Path MTU is below 1500 — ensure PMTUD works or clamp TCP MSS, or large packets will black-hole.

Applied overheads

EncapsulationBytes
802.1Q VLAN tag−4