a_config.gateway.json_ipv6_recipe.txt

# Tutorial - IPv6 through CenturyLink via 6rd on UniFi Security Gateway
# Hello, everyone! I was able to get my UniFi Security Gateway 3P to work with IPv6 on CenturyLink gigabit fiber by using 6rd, after a lot of 
# research and pulling my hair out in frustration. To save others in my situation from the same, I created a config.gateway.json file for you
# to use, as well as a tutorial for modifying the json file to suit your environment.
# Keep in mind that this assumes that:
# Your WAN interface is pppoe2
# Your LAN interface is eth1
# Your tunnel name is tun0
# (If the interface names change, you'll have to modify the JSON file itself accordingly.)
# First step is to go here: http://silmor.de/ipaddrcalc.html#ip46
# Expand "IPv4 to IPv6 Transitional" and look below "6to4 and 6RD Network Prefix"
# For Provider prefix IPv6, enter 2602::/24 (with the subnet in the next box)
# For Customer IPv4, enter your WAN IPv4 address. This will be used to generate your IPv6 prefix. You will want to use 64 bits.
# Then, click ISP -> Customer and it will generate your IPv6 Customer Prefix. Make a note of it (and leave out the :: at the end)
# Here is the JSON. Please use Find/Replace to replace the following placeholder names:
# [IPV4_LAN_SUBNET] = Your USG's internal IP and subnet. i.e.: "192.168.0.1/24"
# [IPV6_PREFIX] = Your IPv6 Customer Prefix that you generated in Step 4

# Links:
# http://silmor.de/ipaddrcalc.html#ip46
# https://www.altibox.no/privat/bredband/ipv6/
# https://community.ubnt.com/t5/EdgeRouter/IPv6-6rd-setup-configuration-writeup/td-p/2052351
# https://www.reddit.com/r/Ubiquiti/comments/9dyjep/tutorial_ipv6_through_centurylink_via_6rd_on/

config.gateway.json

{
	"interfaces": {
		"ethernet": {
			"eth0": {
				"address": [
                    "10.0.0.1/24",
                    "0123:4567:89ab:cdef::1/64"
				],
				"ipv6": {
                    "dup-addr-detect-transmits": "1",
                    "router-advert": {
                            "cur-hop-limit": "64",
                            "link-mtu": "1472",
                            "managed-flag": "false",
                            "max-interval": "300",
                            "other-config-flag": "false",
                            "prefix": {
                                    "0123:4567:89ab:cdef::/64": {
                                            "autonomous-flag": "true",
                                            "on-link-flag": "true",
                                            "valid-lifetime": "2592000"
                                    }
                            },
                            "radvd-options": [
                                    "RDNSS 2001:4860:4860::8888 2001:4860:4860::8844 {};"
                            ],
                            "reachable-time": "0",
                            "retrans-timer": "0",
                            "send-advert": "true"
                    }
				}
			}
		},

		"tunnel": {
			"tun0": {
                "6rd-default-gw": "::5.6.7.8",
                "6rd-prefix": "0123:4567::/30",
                "address": [
                        "0123:4567:89ab:cdef::1/30"
                ],
                "description": "IPv6 6rd tunnel",
                "encapsulation": "sit",
                "local-ip": "1.2.3.4",
                "mtu": "1472",
                "multicast": "disable",
                "ttl": "255",
				"firewall": {
					"in": {
						"ipv6-name": "WANv6_IN"
					},
					"local": {
						"ipv6-name": "WANv6_LOCAL"
					},
					"out": {
						"ipv6-name": "WANv6_OUT"
					}
				}
			}
		}
	}
}