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MTU / Fragmentation Tester
MTUfragmentationIPsecGREWireGuardPMTUDcellulartunnelbranch WAN
Updated Apr 8, 2026
Enter your interface MTU and tunnel type to calculate the effective MTU and safe payload size after encapsulation overhead. Identifies fragmentation risk, explains DF bit implications, and provides recommended MTU values for cellular WAN tunnel configurations.
Supports IPsec Transport, IPsec Tunnel, GRE, WireGuard, and manual overhead entry. Shows full derivation formula and warns when configurations will cause silent PMTUD failures.
MTU / Fragmentation Tester
Calculate the effective MTU and safe payload size for your cellular WAN tunnel configuration to identify fragmentation risk.
Full IP header + ESP — ~80 bytes