Remote Connectivity.

Refer the exhibit above:

PC2 is located in UK and has a public IP address assigned by the respective ISP. The ADSL router in India also has a public IP address from the respective ISP in India.  The ADSL router is configured for PAT (Port address translation). PC1 has a private IP address and has a Web Server enabled.

Questions

1. What should be done in the above configuration so that the web server on PC1 is accessible to PC2.

2. What would be the source IP address of an IP packet which sends data from PC1 to PC2 when it reaches PC2.

3.  Should PC1 have a public IP address for it to be accessible by PC2.

4. How does an IP packet initiated from PC1 reach PC2.

5. How does PC2 know the IP address to reach PC1

Answers

1. The router should be configured for port-forwarding feature. The internal IP address of PC1 should be mapped to correct port; In this case, the web server port which is TCP port 80

2. The source IP address of the IP packet would be the routers public IP address. This is because the private IP address of PC1 would be translated at the router's interface before it exits the router.

3. It is not necessary for PC1 to have a public IP address. Port forwarding can be configured for the internal private IP address.

4. The IP packet initiated from PC1 to PC2 would be send to the router. On the router, PAT would be applied on the IP packet, which would translate the source IP address in the IP packet. After this process, the default route on the router would forward the packet to it's default gateway, which would then forward to it’s gateway and ultimately the packet would reach the destination. (PC2)

5. In the above scenario, PC1 has a private IP address. So PC2 would need to know the IP address of the ADSL router which would then forward the packet to PC1 since port forwarding is configured on it.