Today in our newest take on “older technology is better”: why NAT rules!

  • Brkdncr@lemmy.world
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    4 months ago

    If you use a single shared public ip then you’re using some amount of address translation.

    If you’re using an external ip address that’s different than an internal ip address but both are assigned to a single host the you’re doing 1:1 NAT.

    At least that’s how I understand ipv4 and I don’t think ipv6 is much different.

    • dan@upvote.au
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      4 months ago

      If you use a single shared public ip then you’re using some amount of address translation

      This is practically never the case with IPv6. Usually, each device gets its own public IP. This is how the IPv4 internet used to work in the old days (one IP = one device), and it solves so many problems. No need for NAT traversal since there’s no NAT. No need for split horizon DNS since the same IP works both inside and outside your network.

      There’s still a firewall on the router, of course.

      At least that’s how I understand ipv4 and I don’t think ipv6 is much different.

      With IPv6, each network device can have multiple IPs. If you have an internal IP for whatever reason, it’s in addition to your public IP, not instead of it.

      IPs are often allocated using SLAAC (stateless address auto config). The router tells the client "I have a network you can use; its IP range is 2001:whatever/64, and the client auto-generates an IP in that range, either based on the MAC address (always the same) or random, depending on if privacy extensions are enabled - usually on for client systems and off for servers.

      • Brkdncr@lemmy.world
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        4 months ago

        Just like ipv4 though, you wouldn’t use external addresses internally because your external IPs might change, such as when moving between ISPs. You would NAT a hosts external address to its internal address.

        • dan@upvote.au
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          4 months ago

          your external IPs might change, such as when moving between ISPs

          This is true

          You would NAT a hosts external address to its internal address.

          This is usually not true.

          If you’re worried about your external IP changing (like if you’re hosting a server on it), you’d solve it the same way you solve it with IPv4: Using dynamic DNS. The main difference is that you run the DDNS client on the computer rather than the router. If there’s multiple systems you want to be able to access externally, you’d habe multiple DDNS hostnames.