Does GRE carry gre identifier after It is fragmented?
According to packet size and MTU setting decide whether it is fragmented. If it is fragmented, obey the following rules:
1. Before starting tunnel, tag gre identifier and fragment tunnel packet. Only the first fragmented packet carries gre identifier and subsequent ones do not.
2. If the tunnel is not started, first fragment and then tag gre identifier. And then every fragmented packet carries gre identifier.