I am working through my CCNA and came across the concept that the internet layer adds the source and destination IP to the Frame header.
For example, if the computer's internal IP is say 10.1.0.211 and the destination is say Google DNS which might be 22.214.171.124.
So even though the packet leaves the internal network the CCNA course explains the source and destination IP remains the same. Only the MAC addresses change each hop to the destination. Say your are pinging 126.96.36.199 from 10.1.0.211. How does 188.8.131.52 know where to reply to since 10.1.0.211 is an internal IP address and not externally routable?
It seems like somewhere the external IP address of the router on the internal network would have to be added, but the CCNA course doesn't say that. Otherwise, how would 184.108.40.206 know where to respond?
Is that true then that there is an internal IP and an external source IP get added to the packet at the internet layer for packets that leaves an internal network? If not, how does the destination computer know where to reply to?
Thanks for your help in advance,