Which statement is correct about IP-IP tunnels?
Which statement is correct about IP-IP tunnels?
IP-IP tunnels are specifically designed to encapsulate IP traffic. This encapsulation allows IP packets to be sent securely across a network that may not directly support the original IP packets. Other options, such as encapsulating non-IP traffic and modifying the TTL in transit, do not accurately describe the function and behavior of IP-IP tunnels.
C. The TTL in the inner packet is decremented during transit to the tunnel endpoint. IP-IP tunnels encapsulate IP packets within other IP packets, allowing them to traverse networks that wouldn't normally support the original IP packets. This encapsulation involves the TTL (Time-to-Live) of the inner packet being decremented as it traverses through the tunnel towards its endpoint.
Overhead is 20 bytes, not 24 as GRE
In IP-to-IP as with GRE the inner packet TTL is not decremented. The encapsulating packet TTL is just like any other IP packet. The most correct answer is A.
A is correct
Correct: A
Answer C isn't correct, because it suggests that TRANSIT ROUTERS decrement TTL of the inner packet. Think about it - transit routers would need to be aware of the tunneling, to modify inner IP packet fields - the point of tunneling protocols is to make the inner packet transparent for the transit/underlay network. From Juniper Learning Portal: "The ENCAPSULATOR does not change the inner IP header, except to decrement the TTL and it remains unchanged during its deliver to the endpoint" - only router that encapsulates the inner packet decrements its TTL - during transit, the inner packet is unchanged. Because of that, the correct answer is A - as the name suggests, IP-IP tunneling isn't protocol-agnostic - it can only tunnel IP traffic.
Answer C isn't correct, because it suggests that TRANSIT ROUTERS decrement TTL of the inner packet. Think about it - transit routers would need to be aware of the tunneling, to modify inner IP packet fields - the point of tunneling protocols is to make the inner packet transparent for the transit/underlay network. From Juniper Learning Portal: "The ENCAPSULATOR does not change the inner IP header, except to decrement the TTL and it remains unchanged during its deliver to the endpoint" - only router that encapsulates the inner packet decrements its TTL - during transit, the inner packet is unchanged. Because of that, the correct answer is A - as the name suggests, IP-IP tunneling isn't protocol-agnostic - it can only tunnel IP traffic.