IP masquerading

What will be an ideal response?

This is an extreme case of address translation where a multiple number of IP addresses map onto just a single IP address. For each outgoing packet the source IP address is replaced by the router’s (external) IP address, and the source port is exchanged against an unused port from the range reserved
exclusively for masquerading on the router. If the destination IP of an incoming packet is the local router IP and the destination port is inside the range of ports used for masquerading on the router, the NAT router checks its masquerading table if the packet belongs to a masqueraded session; if this is the case, the destination IP and port of the internal host is inserted and the packet is sent to the internal host.