I did some math a while back. IPv6 will 'never' run out of addresses? Hah! It'll happen sooner than anyone thinks.
- Assume 2^31 IPv6 LANs attached to the internet around the world. - Compute 2^31 * 2^64 = 2^95 addresses assigned - Assume 16 devices connected on each LAN: 2^31 * 2^4 = 2^35 addresses in use Converting to decminal, about 40 * 10^27 addresses assigned, 34 * 10^9 addresses used. That leaves about 1.2 quintillion times the number of addresses in use that will never be used. Had they used /96 as the standard size (32-bit host address), that would've resulted in about 2^63 addresses assigned for the same 2^35 addresses used. The wastage would've dropped to about 270 million times the addresses used: about 12 orders of magnitude less address wastage. My opinion on this in more detail: http://murent.us/#ipv6wastage. I read somewhere that some may be second-guessing that decision. They might've done better to use /96 and hash the MAC address down to 24 bits to make SLAAC work. Neal On Tue, 20 Jun 2023 15:05:07 -0700 Eric Fahlgren <ericfahlg...@gmail.com> wrote: > Yeah, some of the RFCs on v6 address formats hem and haw about how big the > network ID and interface ID parts are (probably written before actual > implementations were in place), but > https://www.rfc-editor.org/rfc/rfc4291#section-2.5.1 says quite > unequivocally: > > For all unicast addresses, except those that start with the binary > value 000, Interface IDs are required to be 64 bits long... > > Which drives a stake in the ground regarding how to partition those 128 bits. > > > On Tue, Jun 20, 2023 at 11:59 AM Petr Menšík <pemen...@redhat.com> wrote: > > > I think that is required by SLAAC RFC, which adds another 2 bytes to 6 > > bytes of hardware ethernet address. > > > > Which is in total 8 bytes, therefore 64 bits is required for it. Prefix > > cannot be higher, but can be lower in theory. There might be some > > implementation details now supporting lower prefix length in current > > implementation. > > > > Cheers, > > Petr > > On 15. 06. 23 12:07, renmingshuai via Dnsmasq-discuss wrote: > > > > When ra-only, slaac, or ra-stateless is configured in dhcp-range and the > > prefix len is set to a value other than 64, like this: > > > > “dhcp-range=2000:1000:1000:1000:1000:1000::, ra-stateless,120,infinite” > > > > the following error message is displayed: > > > > dnsmasq: prefix length must be exactly 64 for RA subnets at line 16 of > > /etc/dnsmasq.conf > > > > Why must the prefix length be 64? This may come from an RFC regulation or > > recommendation, but I didn't find it. Would you mind tell me the reason? > > > > -- > > Petr Menšík > > Software Engineer, RHEL > > Red Hat, http://www.redhat.com/ > > PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB > > > > _______________________________________________ > > Dnsmasq-discuss mailing list > > Dnsmasq-discuss@lists.thekelleys.org.uk > > https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss > > _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
