For a IP over GRE tunnel, as defined by the RFC 2784, the "protocol" field is filled with 0x0800 (defined as ETH_P_IP in the Linux kernel according to this source http://www.scs.stanford.edu/histar/src/uinc/linux/if_ether.h)
I have looked online, but the GRE RFC did not specify which protocol type should be used in the GRE header for an Ethernet over IP tunnel. There doesn't seem to be any good definition in the if_ether.h file either. What should the proper protocol type be for an Ethernet over GRE tunnel?
