Four dimensions
Sizing NAT requires looking at throughput, sessions, ports and addresses together.
Throughput
Measure peak traffic that will pass through NAT, excluding traffic that will use IPv6 or stay on-net.
Concurrent sessions
Each subscriber may have hundreds of active connections — streaming, messaging, background updates. Multiply by peak concurrent subscribers to estimate total sessions.
Ports per subscriber
Each public IPv4 address has around 64,000 usable ports. Allocating, for example, 1,000–2,000 ports per subscriber gives a sharing ratio in the dozens. Too few ports cause failures for heavy users; too many waste addresses.
Address pool
Divide subscribers by your chosen sharing ratio to estimate how many public addresses you need.
Headroom
Leave margin for growth and for events — big matches or releases can spike usage.
Peer1IX NAT Gateway scales these dimensions as a managed service. Request a sizing review.
