Advanced users • Re: Use a random IPv6 interface ID?

Putting your configuration in a file under the /etc/NetworkManager/conf.d directory would probably be safer

Thanks, done.

Now, why Network Manager is doing something different with ipv6.addr-gen-mode=1 and ipv6.addr-gen-mode=stable-privacy is above my pay grade but perhaps it's that ipv6.addr-gen-mode is expecting an int32 (0,1,2,3) in the conf file so by using the words stable-privacy the setting is ignored, defaulting to to eui64. Just a thought. https://www.networkmanager.dev/docs/api ... -ipv6.html

It's the man 5 nm-settings (below) that's not making it clear whether words or numbers are required, and, the change from 1 to stable-privacy by the system!

addr-gen-mode
Configure method for creating the address for use with RFC4862 IPv6 Stateless Address Autoconfiguration. The permitted values are:
NM_SETTING_IP6_CONFIG_ADDR_GEN_MODE_EUI64 (0),
NM_SETTING_IP6_CONFIG_ADDR_GEN_MODE_STABLE_PRIVACY (1).
NM_SETTING_IP6_CONFIG_ADDR_GEN_MODE_DEFAULT_OR_EUI64 (2) or
NM_SETTING_IP6_CONFIG_ADDR_GEN_MODE_DEFAULT (3).

It would have been very helpful if the man page made clear that the permitted values are 0, 1, 2 & 3, just like it did with the ipv6.ip6.privacy information (below)! And, for the life of me I can't understand why stable-privacy and prefer temporary addresses aren't the default settings.

ip6-privacy
Configure IPv6 Privacy Extensions for SLAAC, described in RFC4941.
If enabled, it makes the kernel generate a temporary IPv6 address in addition to the public one generated from MAC address via
modified EUI-64. This enhances privacy, but could cause problems in some applications, on the other hand. The permitted values are: -1:
unknown, 0: disabled, 1: enabled (prefer public address), 2: enabled (prefer temporary addresses).

Myself, with the setting I posted I have 2 ULA's , 2 globally routable addresses and 1 link local address. None of these contain any part of the MAC address in them.

I don't use ULA's, so perhaps that why my link-local and one GUA use the MAC address.

Suggest checking the system logs for NetworkManager errors when making conf file changes. Easier to have NM tell you what it did (or failed to do) is quite simple, since NM is very good about logging things.

journalctl -b | grep NetworkManager

Thanks. Unfortunately there wasn't any helpful information in it.

Statistics: Posted by jeremym — Sat Apr 19, 2025 4:27 am

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