How to use own IPv6 DNS server with a track LAN interface?

[Mr_Sjappie]

Hi,

I have IPv6 successfully working on my OPNsense router with KPN fiber internet using the option: "IPv6 Configuration Type Track Interface" on the LAN interface.

The computers on my LAN get a IPv6 address and the IPv6 DNS server points to the IPv6 address of my OPNsense. And that works. But I want the LAN clients to get a different IPv6 DNS server. I want to use my Pi-Hole setup also for IPv6, now it only works for IPv4.

Is there a way to override the IPv6 DNS server given out by the DHCP track interface?

With kind regards,

Remco

[gpb]

I put ipv6 dns address in router advertisements and system dns.  To put them in radvd settings you need to enable manual settings in the interface settings page.  Then you’ll see a new page in services where you can add dns addresses.  You can also add a nat rule to capture dns inbound lan interface not from your rpi and route them to the rpi.  I have two rules, one for ipv4 and one for ipv6.  Works great.

[robgnu]

Hi,
yes, you can enable Router Advertisements in your Interface settings as described in the first anwer. After that you should try the following config in "Services"->"Router Advertisements"->"[LAN]":

- Router Advertisements: Unmanaged
- Router Priority: Normal
- Advertise Default Gateway: checked
- DNS server: <enter your pihole ipv6 address here>

The other options can remain the default values.

Bye
Robert

ps. there is currently an issue with the radvd daemon, which will break IPv6 connectivity on a regular base on 20.7.x. There are multiple threads in this forum and there is a Github issue, too. https://github.com/opnsense/core/issues/4338

[Mr_Sjappie]

Thnx!

Experimenting with it now... 

[gpb]

I neglected to mention and maybe this was the crux of your question...which ipv6 address do you use for your rpi.  If that's what you're asking, just use the link local (fe80...) address, that should never change (at least that's my understanding) since it's tied to the mac address.  Global unicast address will change so I don't think you can use those unless there's some automated way to update.  You can get that address from your rpi using ifconfig.  Cheers.

[skywalker007]

This (the link local address) only works if pihole is within the same VLAN.
There is another thread covering this topic somewhere which covers the challenge of having this setup configured with multiple VLANs. I never got that running stable. I have shut off pihole for now and replaced it with NextDNS.
I may pick the topic up again later.

[gpb]

This (the link local address) only works if pihole is within the same VLAN.

Thanks...useful tip.

[wilj81]

Old thread, but I was following this.

I have found that if I make any changes to radvd settings IPv6 quits working on Windows 10 (and possibly elsewhere). Any attempt to renew6 leads to the following error message.

Code: [Select]

An error occurred while renewing interface Ethernet : The semaphore timeout period has expired.