I was recently having some trouble with older versions of Android (on rooted Amazon Fire HD8 hardware to be honest) being unable to access the internet on the home network.
A little investigation revealed that they were getting incorrect IPv6 DNS server information. As shown below from NetworkManager on a Linux computer.
root@oxcart:~# nmcli dev show | grep -i dns
IP4.DNS[1]: 172.24.32.254
IP6.DNS[1]: fe80::218:aff:fe84:3af1
IP6.DNS[2]: fe80::218:aff:fe84:444
IP6.DNS[3]: fe80::e8d:dbff:fe17:feee
The fe80 prefix indicates that it’s somewhere on my local subnet, being a link-local address.
The last part of the IPv6 address is conveniently and usually the MAC address, so some poking with ARP revealed that the three dodgy IPv6 DNS servers being advertised were my OpenWRT Meraki wireless access points.
There was no DNS server running on them, hence the failures. This appears to have been advertised from each of them by the odhcpd-ipv6only package.
One quick opkg remove odhcp-ipv6only later, and a renew/reload of client network configuration, and life returns to normal.
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