Unable to Block DNS from IPv6 Router Advertisements

Installing and Using OpenWrt Network and Wireless Configuration
1

I have a dual stack IPv4/IPv6 configuration on my ISP router and behind that is my OpenWrt router that is in my ISP router's DMZ so that I can at least still do the firewalling from OpenWrt. On the OpenWrt WAN interfaces I have a static WAN IPv4 and a DHCPv6 client named wan6. wan6 is set as the designated master for downstream interfaces with the private interface set to relay along with DHCP6 in server mode as I would like to use a static IP addresses.

The problem I'm having is clients computerw are still defining DNS6 from the link-local address of my ISP router through router advertisements. I found a similar forum post here at Stack Exchange and also found an OpenWrt forum post here talking about using the ra_dns='0' option in /etc/config/DHCP but I'm still not having any luck.

/etc/config/network

config interface 'loopback' 
	option device 'lo' 
	option proto 'static' 
	option ipaddr '127.0.0.1' 
	option netmask '255.0.0.0'

config globals 'globals' 
	option ula_prefix 'fdb0:dc72:61cd::/48'

config device 'br0' 
	option type 'bridge' 
	option name 'br0' 
	list ports 'lan1' 
	list ports 'lan2' 
	list ports 'lan3' 
	list ports 'lan4' 
	list ports 'wan'

config bridge-vlan 'private_device' 
	option device 'br0' 
	option vlan '5' 
	list ports 'lan1:t' 
	list ports 'lan2:t' 
	list ports 'lan4'

config interface 'private' 
	option proto 'static' 
	option device 'br0.5' 
	option ipaddr '192.168.5.1' 
	option netmask '255.255.255.0' 
	option broadcast '192.168.5.255' 
	option ip6assign '64' 
	option ip6hint '5' 
	option ip6ifaceid '::1' 
	option delegate '0'

config bridge-vlan 'guest_device' 
	option device 'br0' 
	option vlan '6' 
	list ports 'lan1:t' 
	list ports 'lan2:t' 

config interface 'wan' 
	option device 'br0.20' 
	option proto 'static' 
	option ipaddr '192.168.20.1' 
	option netmask '255.255.255.0' 
	list dns '208.67.220.220' 
	list dns '208.67.222.222' 
	option delegate '0' 
	option gateway '192.168.20.253'

config interface 'wan6' 
	option device 'br0.20' 
	option proto 'dhcpv6' 
	option reqprefix 'auto' 
	option reqaddress 'none' 
	option peerdns '0' 
	list dns '2620:119:35::35' 
	list dns '2620:119:53::53'

/etc/config/dhcp

config dnsmasq 
	option domainneeded '1' 
	option localise_queries '1' 
	option rebind_protection '1' 
	option rebind_localhost '1' 
	option local '/lan/' 
	option domain 'lan' 
	option expandhosts '1' 
	option authoritative '1' 
	option readethers '1' 
	option leasefile '/tmp/dhcp.leases' 
	option resolvfile '/tmp/resolv.conf.d/resolv.conf.auto' 
	option localservice '1' 
	option ednspacket_max '1232'

config dhcp 'wan' 
	option interface 'wan' 
	option ignore '1'

config dhcp 'wan6' 
	option interface 'wan6' 
	option ignore '1' 
	option ra 'relay' 
	option master '1' 
	option start '100' 
	option limit '150' 
	option leasetime '12h' 
	option ra_dns '0' 
	option ndp 'relay' 
	list ra_flags 'none'

config odhcpd 'odhcpd' 
	option maindhcp '0' 
	option leasefile '/tmp/hosts/odhcpd' 
	option leasetrigger '/usr/sbin/odhcpd-update' 
	option loglevel '4'

config dhcp 'private' 
	option interface 'private' 
	option leasetime '12h' 
	option start '20' 
	option limit '150' 
	option dhcpv6 'server' 
	option ra 'relay' 
	option ra_dns '0' 
	list ra_flags 'none' 
	option ndp 'relay'
2

You have relay set.

3

How do I pull the global prefix from my ISP router to OpenWrt so that the clients can achieve IPv6 interconnectivity without using the relay?

4

I'm confused. From what I can see, you need that setting - I understood your issue to be that of the advertising the DNS. But you're not advertising, the ISP is.

5

Well I'm trying to think of another way of achieving IPv6... Is there a way of dynamically retrieving the global prefix so that it can be used to prefix all downstream interfaces?