In the following I explain how IPv6 can be configured in opnsense in addition to IPv4. The instructions are generally valid, but I have used them specifically for my Starlink connection. Before you start setting up IPv6, the IPv4 connection should already be configured as explained in my other article.
First we need to enable IPv6 within our OPNsense installation, this is done in two short steps:
- Under System -> Settings -> General, "Prefer IPv4 over IPv6" must not be selected and further down the page, "Allow DNS server list to be overridden by DHCP/PPP on WAN" must be activated.
- Under Firewall -> Settings -> Advanced we have to allow IPv6 traffic in principle by activating "Allow IPv6".
OPNsense is now IPv6 capable. This is followed by the configuration of the interfaces and gateway. As already mentioned, these instructions are not only valid for Starlink, you can also use them with DSL or fibre optics, provided the provider offers an IPv6 network.
We start in the interface under Interfaces -> [WAN] by setting "IPv6 Configuration Type" to DHCPv6. Then we scroll down and define the details in the section "DHCPv6 client configuration":
- Configuration Mode: Basic
- Request only an IPv6 prefix: Enable
- Prefix delegation size: 56
- Send IPv6 prefix hint: Enable
- Use IPv4 connectivity: Activate
- Use VLAN priority: Disable
Finally, we go to Interfaces -> [LAN]. There we set "IPv6 Configuration Type" to "Track Interface". At the end of the page in the section "Track IPv6 Interface" we select the interface we just configured as "IPv6Interface" and enter 0 as "IPv6 Prefix ID".
That was it! It may be sufficient to reload the interfaces, otherwise restart OPNsense and from then on the connected clients should be assigned an IPv6 address.
You can test this on websites such as What is my IP Address? (ip6.me)
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