Comment plusieurs appareils partagent une adresse publique via le NAT, et le rôle de la passerelle.
NAT et passerelles
En bref
Objectifs
- Expliquer le NAT en une phrase
- Décrire le rôle de la passerelle
- Expliquer l'effet pare-feu du NAT
Your home has one public IP address but many devices. NAT (Network Address Translation) is the trick that lets them share it: your router rewrites the private source address on the way out and remembers the mapping so replies come back to the right device.
The gateway is the router that traffic goes through to leave the local network. When a packet is not for the local subnet, it is sent to the gateway, which forwards it onward.
Note
NAT is why you cannot usually connect to a home device from outside — there is no public address for it. This is a side-effect that happens to provide a crude firewall.
À retenir
- Le NAT réécrit les adresses privées pour partager une IP publique
- La passerelle sort le trafic du réseau local
- Le NAT bloque incidemment les connexions entrantes