My OS X machine gets assigned two public IP addresses from Android 7.1.1:

% ifconfig en0
    ether 8c:29:XX:XX:XX:XX 
    inet6 fe80::8e29:XXff:feXX:XXXX%en0 prefixlen 64 scopeid 0x4 
    inet netmask 0xffffff00 broadcast
    inet6 2607:fb90:4bYY:YYYY:8e29:XXff:feXX:XXXX prefixlen 64 autoconf 
    inet6 2607:fb90:4bYY:YYYY:d427:13ba:ZZZZ:ZZZZ prefixlen 64 autoconf temporary 
    nd6 options=1<PERFORMNUD>
    media: autoselect
    status: active

The problem I've encountered is that the temporary one may change with sleep/wake, whereas the permanent one still has the prefix that is not guaranteed to stay the same (it depends on ME).

I want to use the non-temporary address for ssh, or, at least, extend the time during which the temporary address stays the same (e.g., let's say, to get it automatically hardcoded until the /64 prefix gets reassigned upstream). How?!

As a sidenote, I'm trying to make it easier to identify my ssh connections from within the cloud, as well as make my ssh connections not break between short sleeps; it seems there's an ssh_config(5) option called BindAddress, and it does appear to work (ssh -oBindAddress=2607:fb90:4b61:7474:8e29:XXff:feXX:XXXX …), but I'd prefer to have this configured without hardcoding the prefix that's still temporary in nature. E.g., the solution I'm looking for likely involves system preferences; it's OK if it's not exclusive to ssh.

1 Answer 1


A similar question on SuperUser prompted me to look into sysctl settings, with the following setting available to prefer the permanent IPv6 autoconf addresses to the temporary ones:

% sudo sysctl -w net.inet6.ip6.prefer_tempaddr=0
net.inet6.ip6.prefer_tempaddr: 1 -> 0

For ssh sessions that aren't expecting any ongoing interaction, this would make it possible to go to sleep, and wake up within a number of minutes without any SSH connections suffering a disconnect (which would previously happen due to the prior IPv6 address being de-provisioned upon the wakeup from sleep). (Don't need no mosh!)

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