Omnia announces fd::/8 addresses on lan

A few weeks baxk Omnia suddenly started to announce fd::/8 addresses on the lan interface.
fd::/8 are ULA (Unique Local Addresses)
I wouldn’t care so much, but it also started to announce it’s own fd::/8 address as DNS.
Which is definitely not what I want.
How can I stop my router from advertising itself as DNS or alternatively from announcing fd::/8 addresses at all?

Update: I managed to remove the fd::/8 addresses, but now the router advertises it’s global ipv6 address as DNS.

This is standard behaviour of OpenWRT since 14.07 Barrier Breaker. It strange that your router started announcing it just few weeks ago, mine has been doing it for last 7 years.

Anyway, you already found out how to remove this address, probably by removing the option ula_prefix from /etc/config/network.

Now, If you want your router to announce different IPv6 address as DNS server, you can set it up in /etc/config/dhcp:

config dhcp 'lan'
	option interface 'lan'
	option start '100'
	option limit '150'
	option dhcpv6 'server'
	option ra 'server'
	option ignore '0'
	option leasetime '43200'
	list dhcp_option '6,'
    list dns '2001:4860:4860::8888'

If you don’t want to announce any IPv6 DNS server, it should be possible using option dns_service '0'.

Thanks for the fast reply!
Yes, I tries to remove ULA, but that didn’t solve the problem.
I actually use a raspberry pi with pi-hole installed as my primary resolver in the network. Unfortunately does pi-hole not play well with IPv6. So I do not want to announce any IPv6 addresses.
The “option dns_service ‘0’” didn’t work for me.
But list dns ‘192.168.x.x’ did work. Either RA ignores it now or it announces the same address as dhcpv4.