SNAT


Now we are going to move from the filter table to the nat
table.

Only the first packet in a connection traverses the nat table.

The nat table has three chains
PREROUTING
performed before the routinglookup is performed
used for DNAT where we want to change the destination before the packets are routed
POSTROUTING
performed after the routinglookup is performed
used for SNAT (and it's variations)
OUTPUT
used when we want to DNAT locally generated connections. SNAT of locally generated connections is performed in POSTROUTING