Free IP addressing and routing lessonsIP addressing and routing · Stage 2 · NAT, ICMP and IPv6 · Step 1
Network address translation
See how many private hosts share one public address by rewriting ports, and what that breaks. About 12 minutes.
Two hosts behind one NAT both send from source port 51000. How does the router keep their replies apart?
- AIt maps each to a different external port and remembers which is which
- BIt gives each a different public IP address
- CIt uses their MAC addresses
Show the answer
It maps each to a different external port and remembers which is which. The external port is the key into the NAT table.
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