4 ms·

But it does, that's what ::ffff:0:0/96 is for

remram 3y ago
I can't `ping ::ffff:192.168.0.1` and have it ping my router. There is a range reserved for representing IPv4 addresses, but the stack doesn't translate.
- throw0101b 3y ago
  > I can't `ping ::ffff:192.168.0.1` and have it ping my router. How would that even work in theory? How would a ('legacy'?) host that only understands the 32-bit data structure of IPv4 addresses talk to a >32-bit data structure IPv6 addressed host?
  - FuriouslyAdrift 3y ago
    If it truly encapsulated IPv4, then there wouldn't be two stacks. It would be one stack and legacy devices could snip the xtra bits (or have it done for them via a router).
    - deleted 3y ago
      [deleted]
    - icedchai 3y ago
      I'm skeptical. How would the legacy device V4 understand the "extra bits"? How would this work on the same subnet (no router)?
      - FuriouslyAdrift 3y ago
        If it can't natively (by creating a new networking stack), then a router would have to re-write the packet. Endpoint dvices should not be direct peering (security). Always go through either a passthrough inspection device or router.
        icedchai 3y ago
        Endpoint devices peering directly is how things work on most small networks. What you describe would cause more problems than it solves.
    - growse 3y ago
      > (or have it done for them via a router) And then we are back to NAT...
  - rnhmjoj 3y ago
    You need a translator, i.e. a middle host with dual IPv4/IPv6 stack that can convert an IPv4 packet to an IPv6 packet and v.v. By the way, it's not just theoretical, it exists and it has been standardised, see https://nicmx.github.io/Jool/en/intro-xlat.html#ipv4ipv6-translation https://nicmx.github.io/Jool/en/intro-xlat.html#ipv4ipv6-tra...
- rnhmjoj 3y ago
  You can if you have NAT64: $ ping 64:ff9b::1.1.1.1 PING 64:ff9b::1.1.1.1(one.one.one.one (64:ff9b::101:101)) 56 data bytes 64 bytes from one.one.one.one (64:ff9b::101:101): icmp_seq=1 ttl=54 time=10.4 ms 64 bytes from one.one.one.one (64:ff9b::101:101): icmp_seq=2 ttl=54 time=10.0 ms
  - FuriouslyAdrift 3y ago
    And then we are back to NAT...
    - Dagger2 3y ago
      Yes. What were you expecting? There's no way for a v4-only device to reply to a packet from a v6 source address otherwise. The source address has to be mapped to an address the v4-only device understands, and then mapped back again for the reply packets. How else could this work?
  - remram 3y ago
    The NAT64 prefix (64:ff9b::/96) is not the one GP cited (::ffff:0:0/96). Also I don't have NAT64... The fact that ISPs don't provide NAT64 by default is kind of my point.
- loa_in_ 3y ago
  But you can "ping $address" regardless of which IP version it's using. Please, elaborate what are you trying to solve.
  - remram 3y ago
    I didn't say I couldn't type that in... my point was clear to everybody else who responded.
- Dagger2 3y ago
  It does translate, but it doesn't work for ping because ping bypasses most of the stack by sending raw packets. Try something like `telnet ::ffff:192.168.0.1 80`.
  - remram 3y ago
    That does work. Interesting, the OS translates this at the socket level.
FuriouslyAdrift 3y ago
Those aren't publicly routable though... that's the problem.
- coryrc 3y ago
  Couldn't we just make it so?
  - FuriouslyAdrift 3y ago
    If we could get the RFCs changed, sure!
fanf2 3y ago
That part of IPv6 is mostly deprecated. The more modern version is NAT64 which uses 64:ff9b::/96 by default.

I can't `ping ::ffff:192.168.0.1` and have it ping my router. There is a range reserved for representing IPv4 addresses, but the stack doesn't translate.

throw0101b 3y ago
> I can't `ping ::ffff:192.168.0.1` and have it ping my router. How would that even work in theory? How would a ('legacy'?) host that only understands the 32-bit data structure of IPv4 addresses talk to a >32-bit data structure IPv6 addressed host?
- FuriouslyAdrift 3y ago
  If it truly encapsulated IPv4, then there wouldn't be two stacks. It would be one stack and legacy devices could snip the xtra bits (or have it done for them via a router).
  - deleted 3y ago
    [deleted]
  - icedchai 3y ago
    I'm skeptical. How would the legacy device V4 understand the "extra bits"? How would this work on the same subnet (no router)?
    - FuriouslyAdrift 3y ago
      If it can't natively (by creating a new networking stack), then a router would have to re-write the packet. Endpoint dvices should not be direct peering (security). Always go through either a passthrough inspection device or router.
      - icedchai 3y ago
        Endpoint devices peering directly is how things work on most small networks. What you describe would cause more problems than it solves.
  - growse 3y ago
    > (or have it done for them via a router) And then we are back to NAT...
- rnhmjoj 3y ago
  You need a translator, i.e. a middle host with dual IPv4/IPv6 stack that can convert an IPv4 packet to an IPv6 packet and v.v. By the way, it's not just theoretical, it exists and it has been standardised, see https://nicmx.github.io/Jool/en/intro-xlat.html#ipv4ipv6-translation https://nicmx.github.io/Jool/en/intro-xlat.html#ipv4ipv6-tra...
rnhmjoj 3y ago
You can if you have NAT64: $ ping 64:ff9b::1.1.1.1 PING 64:ff9b::1.1.1.1(one.one.one.one (64:ff9b::101:101)) 56 data bytes 64 bytes from one.one.one.one (64:ff9b::101:101): icmp_seq=1 ttl=54 time=10.4 ms 64 bytes from one.one.one.one (64:ff9b::101:101): icmp_seq=2 ttl=54 time=10.0 ms
- FuriouslyAdrift 3y ago
  And then we are back to NAT...
  - Dagger2 3y ago
    Yes. What were you expecting? There's no way for a v4-only device to reply to a packet from a v6 source address otherwise. The source address has to be mapped to an address the v4-only device understands, and then mapped back again for the reply packets. How else could this work?
- remram 3y ago
  The NAT64 prefix (64:ff9b::/96) is not the one GP cited (::ffff:0:0/96). Also I don't have NAT64... The fact that ISPs don't provide NAT64 by default is kind of my point.
loa_in_ 3y ago
But you can "ping $address" regardless of which IP version it's using. Please, elaborate what are you trying to solve.
- remram 3y ago
  I didn't say I couldn't type that in... my point was clear to everybody else who responded.
Dagger2 3y ago
It does translate, but it doesn't work for ping because ping bypasses most of the stack by sending raw packets. Try something like `telnet ::ffff:192.168.0.1 80`.
- remram 3y ago
  That does work. Interesting, the OS translates this at the socket level.

FuriouslyAdrift 3y ago

Those aren't publicly routable though... that's the problem.

coryrc 3y ago
Couldn't we just make it so?
- FuriouslyAdrift 3y ago
  If we could get the RFCs changed, sure!

fanf2 3y ago

That part of IPv6 is mostly deprecated. The more modern version is NAT64 which uses 64:ff9b::/96 by default.