dhcpcd-discuss

You always need router advertisements to inform the nodes of the prefixes and their length to be used. These RAs also inform nodes whether these addresses covered by a prefix are considered to be on-link or not on-link (yeah, they're most probably not off-link, this is a weird three state situation). The RFCs detail this very clearly, and there's even RFC about that this is by design. On an implementation side, RA prefix options trigger route creation, as does the router lifetime of an RA itself.
Back to your DHCPv6 server's pools: you need to carefully match allocation to the RAs, otherwise you end up with useless DHCPv6 assigned addresses. Enjoy the ride of keeping your pools and routers in sync. I suspect ISPs to have their dedicated tools or tool chains foe this, but would like to hear details about this.

Interestingly, around November or December last year, Win10 got support for the RDNSS option in RAs, so Windows now follows suit wrt RA-based autoconfiguration.
Best regards,Harald


-------- Ursprüngliche Nachricht --------Von: jobhunts02@xxxxxxx Datum: 01.03.18  22:24  (GMT+01:00) An: Roy Marples <roy@xxxxxxxxxxxx> Cc: dhcpcd-discuss@xxxxxxxxxxxx Betreff: Re: [dhcpcd-discuss] IPv6 Prefix Length 
How does the subnet prefix defined on the DHCP server for a pool take effect?

For example, if I have 2 different subnets with different prefixes, how would I enforce this?

> On Mar 1, 2018, at 6:28 AM, Roy Marples <roy@xxxxxxxxxxxx> wrote:
> 
>> On 01/03/2018 02:44, jobhunts02@xxxxxxx wrote:
>> On my server in dhcpd6.conf  the prefix length is 64:
>> subnet6 2001:ed8:77b5::/64 {
>>         range6                          2001:ed8:77b5:0:10:123:105:150 2001:ed8:77b5:0:10:123:105:155;
>> }
>> On my client, I am getting an address with a prefix length of 128:
>> inet6 addr: 2001:ed8:77b5:0:10:123:105:155/128 Scope:Global
>> Is this the expected behavior?
> 
> Yes this is expected.
> A DHCPv6 lease is not tied to any specific prefix.
> The kernel will use the longest matching prefix as the out-going route.
> 
> Roy