4 ms·

That’s fine, nat can do that just fine. But ipv6 fans hate nat, so instead we end up with proponents saying “run dual stack” and those who don’t want the added

That’s fine, nat can do that just fine. But ipv6 fans hate nat, so instead we end up with proponents saying “run dual stack” and those who don’t want the added overhead simply ignoring ipv6 entirely

smitty1e 5y ago
It's not just the added overhead. For many, having a *private* IPv4 space is not just a feature, but a requirement. The idea of a completely globally flat address space makes perfect technical sense. However, policy sense may differ as Your Mileage Varies.
- duhast 5y ago
  Nothing in the IPv6 spec forces you to publicly advertise your globally flat address space. Even if you do choose to advertise your prefixes publicly, you can still use firewalls to block some or even all traffic.
  - zinekeller 5y ago
    Not this discussion again. Okay, you can indeed do that... but how do you get an address is the another question. You might answer "Just go to the RIR", sure, but ASNs aren't given willy-nilly, they need to prove that they'll need different routing needs for external peering, and some RIRs do insist on this. The most loose RIR in terns of regulations is RIPE, but what about other companies in other parts of the world?
    - eqvinox 5y ago
      You get your private prefix by appending 10 random hex nibbles to "fd". For example, fdb9:3667:a8da::/48. (Please make your own random prefix.) You also missed the point of this sub-thread since the question was about private space. IPv6 fd00::/8 is IPv4 10.0/8. The only difference is an added bit of semantics to make merging networks easier.
      - iso1210 5y ago
        The problem is that ipv6 advocates say "just have your network auto-renumber itself every time you change upstream provider", "run multiple IP addresses on every host" etc I don't think I've ever seen anyone suggesting using a /48 in fd00:: and NAT66 at the edge, and NAT64 is discouraged rather than maintaining a dual stack solution (and if you need to maintain a working ipv4 solution, why even bother with ipv6)
    - throw0101a 5y ago
      > You might answer "Just go to the RIR", sure, but ASNs aren't given willy-nilly You get an PI address block and ask your ISP to advertise it on your behalf in their public ASN, e.g.: > If multi-homing to more than one provider, the customer must obtain an Autonomous System (AS) number, available at http://www.arin.net http://www.arin.net. If multi-homing only to us, we will provide a private AS number. * https://support.allstream.com/knowledge-base/bgp-request-information/ https://support.allstream.com/knowledge-base/bgp-request-inf...
      - zinekeller 5y ago
        > You get an PI address block and ask your ISP to advertise it on your behalf And? Get nothing in some regions because all of their ISPs aren't willing to provide this service even with money? I know provider-independent addresses, but don't pretend it'll solve the problem of IPv6. The fact that you need to do some service wrangling rather than "take this IP for private use, just don't ask us when IP conflicts happen" (and ULA implementation is inconsistent even in enterprise routers) means headaches abound that didn't exist for IPv4.
- iso1210 5y ago
  fc00::/7 is the space for that private range, it's as routable and subnettable as 10.0.0.0/8
  - cesarb 5y ago
    > fc00::/7 is the space for that private range A small nitpick: the lower part of that range is reserved for future expansion, so the private range is actually fd00::/8. And you should pick a random /48 within that to be your private 10.x.x.x-like range, not use the whole /8. (See https://en.wikipedia.org/wiki/Unique_local_address#Definition https://en.wikipedia.org/wiki/Unique_local_address#Definitio... for more details.)
    - smitty1e 5y ago
      Ecxellent. Learned somthing imprtant today. As long as there is a provision to soak it in CIDR. I had looked at the dual-stack portion of AWS some years ago and did not see how this worked. Doubtless, my oversight.
      - eqvinox 5y ago
        > As long as there is a provision to soak it in CIDR. There is; the idea is to fill up random bits to /48, leaving you with 16 bits of subnetting space until you hit /64. If you're not concerned about aggregating networks, a common pattern on larger networks is to put the VLAN ID there in "false hex", i.e. VLAN 1357 = fd……:1357::/64. If you need more space you can either generate more random /48 prefixes, or widen the prefix length on your existing /48. The latter is technically against the spirit of ULAs, but… only the pedants will care.

smitty1e 5y ago

It's not just the added overhead. For many, having a *private* IPv4 space is not just a feature, but a requirement. The idea of a completely globally flat address space makes perfect technical sense. However, policy sense may differ as Your Mileage Varies.

duhast 5y ago
Nothing in the IPv6 spec forces you to publicly advertise your globally flat address space. Even if you do choose to advertise your prefixes publicly, you can still use firewalls to block some or even all traffic.
- zinekeller 5y ago
  Not this discussion again. Okay, you can indeed do that... but how do you get an address is the another question. You might answer "Just go to the RIR", sure, but ASNs aren't given willy-nilly, they need to prove that they'll need different routing needs for external peering, and some RIRs do insist on this. The most loose RIR in terns of regulations is RIPE, but what about other companies in other parts of the world?
  - eqvinox 5y ago
    You get your private prefix by appending 10 random hex nibbles to "fd". For example, fdb9:3667:a8da::/48. (Please make your own random prefix.) You also missed the point of this sub-thread since the question was about private space. IPv6 fd00::/8 is IPv4 10.0/8. The only difference is an added bit of semantics to make merging networks easier.
    - iso1210 5y ago
      The problem is that ipv6 advocates say "just have your network auto-renumber itself every time you change upstream provider", "run multiple IP addresses on every host" etc I don't think I've ever seen anyone suggesting using a /48 in fd00:: and NAT66 at the edge, and NAT64 is discouraged rather than maintaining a dual stack solution (and if you need to maintain a working ipv4 solution, why even bother with ipv6)
  - throw0101a 5y ago
    > You might answer "Just go to the RIR", sure, but ASNs aren't given willy-nilly You get an PI address block and ask your ISP to advertise it on your behalf in their public ASN, e.g.: > If multi-homing to more than one provider, the customer must obtain an Autonomous System (AS) number, available at http://www.arin.net http://www.arin.net. If multi-homing only to us, we will provide a private AS number. * https://support.allstream.com/knowledge-base/bgp-request-information/ https://support.allstream.com/knowledge-base/bgp-request-inf...
    - zinekeller 5y ago
      > You get an PI address block and ask your ISP to advertise it on your behalf And? Get nothing in some regions because all of their ISPs aren't willing to provide this service even with money? I know provider-independent addresses, but don't pretend it'll solve the problem of IPv6. The fact that you need to do some service wrangling rather than "take this IP for private use, just don't ask us when IP conflicts happen" (and ULA implementation is inconsistent even in enterprise routers) means headaches abound that didn't exist for IPv4.
iso1210 5y ago
fc00::/7 is the space for that private range, it's as routable and subnettable as 10.0.0.0/8
- cesarb 5y ago
  > fc00::/7 is the space for that private range A small nitpick: the lower part of that range is reserved for future expansion, so the private range is actually fd00::/8. And you should pick a random /48 within that to be your private 10.x.x.x-like range, not use the whole /8. (See https://en.wikipedia.org/wiki/Unique_local_address#Definition https://en.wikipedia.org/wiki/Unique_local_address#Definitio... for more details.)
  - smitty1e 5y ago
    Ecxellent. Learned somthing imprtant today. As long as there is a provision to soak it in CIDR. I had looked at the dual-stack portion of AWS some years ago and did not see how this worked. Doubtless, my oversight.
    - eqvinox 5y ago
      > As long as there is a provision to soak it in CIDR. There is; the idea is to fill up random bits to /48, leaving you with 16 bits of subnetting space until you hit /64. If you're not concerned about aggregating networks, a common pattern on larger networks is to put the VLAN ID there in "false hex", i.e. VLAN 1357 = fd……:1357::/64. If you need more space you can either generate more random /48 prefixes, or widen the prefix length on your existing /48. The latter is technically against the spirit of ULAs, but… only the pedants will care.