NAT typically refers to router translating an IP address from a private network to a public IP address so that the node on the private network can access public Internet.
Is there a valid scenario where a router* is used to translate an address from a public IP address to another public IP address?
*note: I am talking about router only, not a proxy.
Best Answer
One scenario that fits your description of "translate an address from a public IP address to another public IP address" happens every time I access StackExchange.
Even though every computer on my network has public IP addresses I cannot access StackExchange directly because StackExchange only supports IPv4. So this answer is being sent through a NAT64 which translates public IPv6 addresses into public IPv4 addresses.
Cases of translating between different public IP addresses within the same protocol also happens. I have come across a company which had a
/8of IPv4 space and assigned addresses from that range to internal hosts. But they still used a NAT to translate the addresses such that externally traffic would be seen originate from an IPv4 address outside of that/8.I don't know why that company chose to use a NAT when they in fact had enough IPv4 addresses to not need it. I think every such deployment could work better without the NAT, but I can't say that with absolute certainty since I obviously don't have intimate knowledge of what happens behind every NAT in the world.