Add ULA address to pfsense LAN

interfaces.conf

# Put in /usr/local/etc/devd/interfaces.conf
# Adds ULA address later - using VIP feature breaks RA of prefix delegated from WAN.
# Based on https://web.archive.org/web/20190811062325/https://old.reddit.com/r/PFSENSE/comments/97b5zj/ipv6_isp_assigned_prefixes_how_to_assign_ip/
notify 1 {
    match "system"        "IFNET";
    match "subsystem"     "igb1";
    match "type"          "LINK_UP";
    action "/sbin/ifconfig igb1 inet6 fd00::1 prefixlen 64 alias";
};