Notes

Knowing the encapsulation overhead of your protocol stack is important for configuring VPN tunnels. You need to set the tunnel interface MTU correctly, to avoid excessive packet fragmentation.

This tool allows you to easily see what each protocol adds to your packet. Click protocol buttons to add protocols to the stack. Some protocols have additional options, e.g. if you click Ethernet, you will see VLAN and QinQ header option checkboxes.

You can click the same protocol button more than once, e.g. for the IPIP encapsulation you just click the IPv4 button twice.

Examples:

• TCP MSS for IPv6 in GRE over IPv4
• MTU for IPv4 in an Ethernet VLAN over L2TPv3 over UDP.

Header sizes for VXLAN, LISP, and WireGuard include UDP, and STT includes TCP, because these protocols never use any other L4 protocol. Everything else is pure header size, without any outer or inner protocols, e.g. “MPLS” is the size of a single MPLS label (4 bytes).