Assume Host A and Host B are on a private network communicating through IP tunneling. A has private IP 172.16.45.90, B has private IP 168.20.30.40, and routers R1 and R2 have public IPs 87.204.189.33 and 203.128.56.77, respectively.
Host A Router R1 Router R2 Host B
_____ _______ _______ _____
| | | | | | | |
| H A |----1-----| R1 |-----2------| R2 |-----3-----| H B |
|_____| |_______| |_______| |_____|
At position 1, what are the source and destination addresses for a packet sent from A to B (src; dest)?
✅ 172.16.45.90; 168.20.30.40
Routers R1 and R2 act as a tunneling network—once they receive an inbound packet, they add another IP layer. This IP layer has the source as the entering router (R1) and the destination as the exiting router (R2). Once a packet leaves the network, the outer IP layer is removed.
Hence, at position 1, it hasn’t interacted with the tunneling network, so the packet is with its original source and destination (A and B).
At position 2, what are the source and destination addresses for a packet sent from A to B (src; dest)?
✅ 87.204.189.33; 203.128.56.77
At position 2, the packet is now in the tunneling network. It has been processed by R1, so it’s new layer has R1 and R2 as the source and destination respectively.
At position 3, what are the source and destination addresses for a packet sent from A to B (src; dest)?
✅ 172.16.45.90; 168.20.30.40
At position 3, the packet has now left the tunneling network. It has been processed by R2, so its new layer is removed. The source and destination is its original: A and B respectively.
Which of the following is least likely to be used by a VPN?
❌ IP Tunneling