JUNOS software performs NAT in the following ways:
Reverse mapping in static NAT—There is no explicit
NAT action in a policy to trigger this type of NAT-src. As long as
the traffic matches a “ permit” policy and reverse mapping
in static NAT is found on the egress interface, the source IP address
will get translated according to reverse mapping.
Source pool defined on egress interface—When
performing source network translation (NAT-src), source pool provides
JUNOS software with a supply of addresses from which to draw. When
a policy requires NAT-src and references a specific source pool, JUNOS
software draws addresses from that pool when translation is performed.
