2

In the below image what would be the ip address in the outer ip header when packet goes from R1 to R2. If the ip address in the outer header is 172.16.0.1 , how does it travels the internet as its not a public ip address ?

enter image description here

Improve this question
1
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin ♦
    Commented Aug 13, 2017 at 5:57

2 Answers 2

Reset to default
2

In the outer IP header, it would definitely be 1.1.1.10 / 2.2.2.10, as this is what is used to route the packet to the tunnel endpoint.

Note that you may not even need IP addresses on the tunnel interfaces, you could use ip unnumbered as it's a point-to-point link.

Improve this answer
2

While Configuring GRE tunnel you may have specify source and destination address. That Source and destination IP are 1.1.1.10 and 2.2.2.10. These IPs will be routed in the internet and helps to bring up GRE tunnel.

Once tunnel is up we can assign IP between two end point which in this case is 172.16.0.0/24 network. So any tunnel with IP address on top of it at the end points are called numbered and without IP are called un-numbered.

Advantage of using ip address on the tunnel interface is, we can run any dynamic routing protocol to route any traffic over the tunnel.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.