Hack the Route Start free Open app Address translation
Static NAT, dynamic NAT and PAT
One address for one device (static), addresses from a pool as devices go out (dynamic), or one address shared by port (PAT).
Cisco names a translated conversation's four addresses from the router's side: inside local (the inside
device's own address), inside global (what the outside sees for it), outside global (the outside device's real
address) and outside local (how the inside sees it; the same unless destinations are rewritten too). Static NAT
maps one inside local to one inside global for good, both ways, so the outside can start a connection: the way to
publish a server. Dynamic NAT hands out inside globals from a pool as inside devices connect, one each on IOS,
and refuses a device when the pool runs out. PAT (IOS overload) shares one address, telling conversations apart
by source port: what nearly every home and office router does. The inside globals must be addresses the outside routes
to the router. On Linux: SNAT (and DNAT for static's inbound half) or MASQUERADE in iptables' nat table, with the
translations in conntrack -L.