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My home machine has two IPv6 address, that look like this (obfuscated for security sake):

2: enp1s0    inet6 2500:1600:4650:bc59::49/128 scope global dynamic noprefixroute \       valid_lft 1127515sec preferred_lft 1127515sec
2: enp1s0    inet6 2500:1600:4650:bc59:1440:adb5:bacb:4447/64 scope global dynamic noprefixroute \       valid_lft 1209597sec preferred_lft 1209597sec
2: enp1s0    inet6 fe80::a42a:340c:d982:163c/64 scope link noprefixroute \       valid_lft forever preferred_lft forever

I get that the last one (fe80) is a link-local address, but the other two- I'm not sure why I have both. My system is a Pi-Hole server, and thus it's a DHCPv6 server (SLAAC+RA turned on).

Could you explain the 2 addresses? I guess the /64 is my host's real IP?

Mike S
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    Excellent. Try to figure out what's going on, get downvoted twice without even any reason given. Way to be, StackExchange! Very helpful on so many levels. I mean, some trivial Bash questions get 55 upvotes: https://unix.stackexchange.com/questions/16024/how-can-i-assign-the-output-of-a-command-to-a-shell-variable . I mean, it's not like this article: https://www.cyberciti.biz/faq/unix-linux-bsd-appleosx-bash-assign-variable-command-output/ hadn't been around years before that question was asked. For pete's sake. Maybe I should have asked something more basic, answered in a man page... – Mike S Jun 19 '18 at 17:48
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    Totally agree, bro. StackExchange is becoming what we used to have on 90's lixux forums. How dare we ask a question on internet instead of going on the internet look for answers?! – Hikari Aug 20 '19 at 16:16
  • @Hikari Yeah, it's even worse than that. If one is ignorant of the situation (as I admit to be) and if one does attempt to spend the time looking for the answer (which I did... I'm not going, "Oh goodie! Now I can ask on StackExchange, where I may or may not get a useful answer in a reasonable timeframe!"), and if one is not able to find such an answer due to one's ignorance, one risks being greeted with the downvote, like, "You IDIOT! Don't you know not to ask dumb questions? What, are you trying to learn???" – Mike S Aug 22 '19 at 15:15

1 Answers1

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You've got two global IPv6 addresses, one assigned by DHCPv6 and the other locally generated (via SLAAC).

By default Fedora 28 generates RFC 7217 stable privacy addresses when told to use SLAAC, so that is why you are getting a privacy address.

Which address actually gets used for outgoing connections is probably not predictable from the limited information provided in the question.

But if you intend to have privacy addresses, you may wish to disable DHCPv6 addressing on the local network.

Michael Hampton
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    Thanks for the reply. I suppose I would be able to give you more information if I know more about IPv6. ;-\ What else would you need to know, to be able to predict which address gets used? Are privacy addresses important in the IPv6 world? – Mike S Jul 11 '18 at 22:59