Description of problem:
Fedora 25 host silently removes statically assigned ipv6 addresses from LAN interfaces after they have been up/initialised for 24 hours.

Not sure of component doing this (its not being logged, they are just disappearing), assuming systemd.


Version-Release number of selected component (if applicable):
systemd-231-12.fc25.i686


How reproducible:
Predictably, after 24 hours.

Steps to Reproduce:
1. Configure ip4 and ipv6 addresses in /etc/systemd/network/10-enp0s18.network as follows:
[Match]
Name=<interface name>
MACAddress=<my interface MAC>

[Network]
Address=<ipv4 address/prefixlen)
Address=<global ipv6 address/prefixlen>
Address=<link-local ipv6 address/prefixlen>
DNS=<my dns 1>
DNS=<my dns 2>
Domains=<my domain search list>

2. Enable systemd-networkd.service, systemd-resolved.service

3. On boot, all three (ipv4, global v6, link-local v6) addresses are assigned to the interface. Allow 24 hours to pass, the global v6 address is REMOVED from the interface with nothing to log what did it or why.

4. Interface flags:
 3: enp0s18    inet <my v4>/24 brd 10.99.99.255 scope global enp0s18\       valid_lft forever preferred_lft forever
 3: enp0s18    inet6 2001:<my global v6>/64 scope global \       valid_lft forever preferred_lft forever
 3: enp0s18    inet6 fe80::<my link-local v6>/64 scope link \       valid_lft forever preferred_lft forever

These interfaces are statically assigned; this machine is a router and is running radvd. 

Actual results:
1. global v6 address silently removed after 24hours of uptime. Can be revived with  ifdown/ifup.

Expected results:
1. These interfaces should not unassign. They are not temporary/privacy addresses.

Additional info:
1. NetworkManger has been removed from this system (so it's not that).
2. sysctl for lifetimes:
- net.ipv6.conf.enp0s18.temp_prefered_lft = 86400
- net.ipv6.conf.enp0s18.temp_valid_lft = 604800

*These are NOT temporary addresses*