Generic Routing Encapsulation - Packet Header

Packet Header

A GRE packet header structure is represented in the diagram below.

Bits 0–4 5–7 8–12 13–15 16–31
C R K S s Recur Flags Version Protocol Type
Checksum (optional) Offset (optional)
Key (optional)
Sequence Number (optional)
Routing (optional)

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