FAQ - Why traffic cannot be transmitted at wire speed when being forwarded through the GRE tunnel

For S series switches excluding the S1700, why traffic cannot be transmitted at wire speed when being forwarded through the GRE tunnel?

When a packet is forwarded through a tunnel, a label is added to the packet at the tunnel egress. That is, the packet length is increased. The GRE tunnel adds 24 or 32 bytes to the original packet, and the length of a label is 4 bytes on the VPN tunnel. In this case, the total traffic exceeds the wire speed. Packets are discarded during forwarding.

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