[Dnsmasq-discuss] Question about IPv6 settings

[Simon Kelley]

On 11/12/2025 13:47, Andreas Kuropka via Dnsmasq-discuss wrote:
> Hello,
> 
> I have one "shared" network with two gateways. Different devices use different gateways.
> 
> Until now I used IPv4 where I was able to set the gateway with the option:router,IP directive. Hosts have tags and for different tags I use different IPs as router.
> 
> Unfortunately the mobile ISP I use switched from dual-stack to IPv6-only (DNS64+NAT64 and 464-XLAT). One router gets 2a01:: addresses, the other one 2003:: ones, both routers have each a fe80:: LL-address which can be used as router option.
> 
> How can I set up dnsmasq that I can set the gateway/router on device/tag-basis as I had with IPv4 until now.
> 
> I would appreciate any help.
> 

You can't control the default router using DHCP, as you can in IPv4, 
since DHCPv6 is not involved in router discovery. That's done using the 
router advertisement protocol.

Each of your routers will be advertising it's own prefix, and it's own 
LL address as router for that prefix, and you have to go with that.

One thing that MIGHT work, is to configure dnsmasq to do DHCPv6, but NOT 
Router advertisement. Configure dnsmasq to give either a 2a01 or a 2003 
addresses as preferred. If you're lucky, the IPv6 stack will use the 
default route associated with the prefix of the address that the host 
has and all will work as desired.

Simon.