Network Address Translation (NAT)

1990s addresses were depleting due to rapid adoption of the internet
- IP was more popular than they tough and they were running out of IP space
IPv6 was being developed, address translation was meant as a temporary solution
- Every digit that we add gives us billions more of possible IPs
RFC 1918 addresses internally
- 192.168..
- 10.0.0..
- Everybody can use these kind of networks internally
  - On your private network you have tons of space but when you want to talk to the rest of the world we are going to translate your private address to a public address
Globally unique addresses will be shared by internal users

No registration required
Internal use
Not routable on pubic Internet
10.0.0.0 /8
172.16.0.0 - 172.31.255.255 /12
- Think about store prices ($31.99), because 32 is the next network
192.168.0.0 /16
- Private space

Internal hosts "borrow" a public IP
Hosts presents itself as this public IP during its session
IP returned to pool after use
- with NAT we have to have a 1-to-1 ratio, one IP per device.

What we do nowadays
1 real-world address shared by many tenants
A single IP is shared across thousands of simultaneous sessions
- 1-65,535 Ports
Each session requires a unique port number
Sessions are tracked and maintained inside a table