In FreeNAS itself (not the jails, not VMs), the default IPv6 gateway will disappear after boot (if it is set at all). Specifically, there is no "default" destination/entry running "netstat -6nr".
- No default gateways set under Network > Global Configuration.
- Under Network > Interfaces > primary interface, "DHCP" and "Autoconfigure IPv6" are checked.
- All network interfaces have IPv6 addresses. rtsold appears to be running (checked with onestatus, since rtsold_enable is not YES).
- Jails and VMs have proper IPv6 connectivity (e.g., "ping6 google.com" works), but FreeNAS itself does not.
The default gateway stops disappearing if I add two tunables "ipv6_activate_all_interfaces" and "rtsold_enable" set to YES (per https://www.ixsystems.com/community/threads/11-3-ipv6-routing-problems.82045/). This is the same configuration I see added to /etc/rc.conf of jails.