Why used DHCPv6 when RA has RDNSS and DNSSL?

[James R Cutler]

> On Mar 30, 2020, at 8:30 PM, Roger Wiklund <roger.wiklund at gmail.com> wrote:
> 
> 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 <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!

I don’t understand why this is a disincentive of any consequence to preparing for the future by adopting IPv6.  

See also: https://apple.stackexchange.com/questions/315232/disable-temporary-autoconf-inet6-address <https://apple.stackexchange.com/questions/315232/disable-temporary-autoconf-inet6-address> (nota bene: I have not checked this on my Catalina systems due to time constraints.)


James R. Cutler
James.cutler at consultant.com
GPG keys: hkps://hkps.pool.sks-keyservers.net
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