Explanation:
3 - R1
2 &4 - R2
5 - R3

NAT use four types of addresses:
* Inside local address - The IP address assigned to a host on the inside network. The address is usually not an IP address assigned by the Internet Network Information Center (InterNIC) or service provider.
This address is likely to be an RFC 1918 private address.
* Inside global address - A legitimate IP address assigned by the InterNIC or service provider that represents one or more inside local IP addresses to the outside world.
* Outside local address - The IP address of an outside host as it is known to the hosts on the inside network.
* Outside global address - The IP address assigned to a host on the outside network. The owner of the host assigns this address.

"In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second." Both standards use Ethernet framing (same headers and trailers)