Exam JN0-362 topic 1 question 31 discussion

When the packet is encapsulated with GRE the original TTL is dectemented to make sure that the packet dows not live forever.

Answer is C and D, ttl is not decremented by encapsulator/decapsulator

+ IP in IP Encapsulation To encapsulate an IP datagram using IP in IP encapsulation, an outer IP header [10] is inserted before the datagram's existing IP header, as follows:

rfc2003 When encapsulating a datagram, the TTL in the inner IP header is decremented by one if the tunneling is being done as part of forwarding the datagram; otherwise, the inner header TTL is not changed during encapsulation. If the resulting TTL in the inner IP header is 0, the datagram is discarded and an ICMP Time Exceeded message SHOULD be returned to the sender. An encapsulator MUST NOT encapsulate a datagram with TTL = 0. The TTL in the inner IP header is not changed when decapsulating. If, after decapsulation, the inner datagram has TTL = 0, the decapsulator MUST discard the datagram. If, after decapsulation, the decapsulator forwards the datagram to one of its network interfaces, it will decrement the TTL as a result of doing normal IP forwarding. See also Section 4.4.