Various different methods of making it go in different distributions
Debian: in /etc/network/interfaces
-- auto enp1s0.2502 - iface enp1s0.2502 inet dhcp - iface enp1s0.2502 inet6 auto -
++auto enp1s0.2502 +iface enp1s0.2502 inet dhcp +iface enp1s0.2502 inet6 auto
OpenWRT has a nice GUI
@@ -156,11 +155,9 @@Static Routes!
Harking back to our vlan
-- ip -6 route add 2001:db8:2501::/64 via 2001:db8:2500::1 dev enp0s1 - ip -6 route add 2001:db8:2502::/64 via 2001:db8:2500::1 dev enp0s1 - ip -6 route add 2001:db8:2600::/64 via 2001:db8:2600:beef:face::1 dev enp0s1 -
+ip -6 route add 2001:db8:2501::/64 via 2001:db8:2500::1 dev enp0s1 +ip -6 route add 2001:db8:2502::/64 via 2001:db8:2500::1 dev enp0s1 +ip -6 route add 2001:db8:2600::/64 via 2001:db8:2600:beef:face::1 dev enp0s1