Basic NAT (cont)

• map to 0/32 is special: is replaced by the IP address of the specified interfaces

• map to 0/0 is also special: no mapping is done (we'll see later why that is handy)

• "map" maps ip numbers in unpredictable ways (first come first serve). It rewrites source addresses on outgoing interfaces

• If a mapping fails, the packet goes through unmodified: use IP filtering as well!