A source network address and port translation (NAPT) mechanism is described that reduces or eliminates the need to log any NAT translations. As described herein, a mapping between a subscriber's private address to a public address and port range is determined algorithmically. Given a particular mapping rule, as specified by the service provider, a subscriber is repeatedly and deterministically mapped to the same public network address and a specific port range for that network address. Once the public address and port range for a subscriber are computed, the particular ports for each session for that subscriber are allocated dynamically within the computed NAT port range on per session basis.