Why used DHCPv6 when RA has RDNSS and DNSSL?

[Roger Wiklund]

Hi

I played around with IPv6 on my Mac today (Mac OS Catalina) and I noticed
that besides the IP from DHCPv6 (dynamic) it's also generating two other
addresses.

ether aa:bb:cc:dd:ee:ff
inet6 fe80::1cad:944f:df4a:d123%en0 prefixlen 64 secured scopeid 0x7
inet6 2001:123:44:55:1a:f346:1bef:b88a prefixlen 64 autoconf secured
inet6 2001:123:44:55:20ac:49d2:68c5:595b prefixlen 64 autoconf temporary
inet6 2001:123:44:55::101 prefixlen 64 dynamic

I don't really know that the "secured" address is used for TBH (both
autoconf are randomized and not based on the MAC)
The temporary address is used for outgoing connections and is changed every
so often.
The dynamic address if from my DHPv6 server.

I think Windows has the same behaivour.

This got me thinking, if the temporary address is used as the outgoing
source address, this gives me even less incentive to use DHCPv6. Especially
since my Juniper SRX supports RDNSS via RA:
https://tools.ietf.org/html/rfc8106

set protocols router-advertisement interface ge-0/0/0.20 dns-server-address
2001:4860:4860::8888 lifetime 3600
set protocols router-advertisement interface ge-0/0/0.20 dns-server-address
2001:4860:4860::8844 lifetime 3600
set protocols router-advertisement interface ge-0/0/0.20 prefix
2001:123:44:55::/64

When I read DHCPv6 vs SLAAC it often boils down to "control" but I don't
see the need to allocate a dynamic address if the autogenerated are used.
For client's you dont really have any inbound connections unless it's a
support case.

What's your view on this?

Thanks!
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