[Dnsmasq-discuss] Why does the dnsmasq routing feature require a subnet prefix length of 64?

[Petr Menšík]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/attachments/20230620/252c28a7/attachment.htm>