IPv4 blocks IPv6 dns lookups

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http://askubuntu.com – I'm using a IPv4 + IPv6 on a server (#1). Sometimes the IPv4 address is mapped to another server (#2), so #1 isn't accessible via IPv4, but remains accessible via IPv6. In this case IPv6 dns lookups won't work. $ ping6 mirror.ipv6.hetzner.de unknown host If I disable the IPv4 address everything works fine. $ ping6 mirror.ipv6.hetzner.de PING mirror.ipv6.hetzner.de(2a01:4f8:0:a101::1:1) 56 data bytes 64 bytes from 2a01:4f8:0:a101::1:1: icmp_seq=1 ttl=60 time=0.469 ms How is this possible? The IPv6 network should serve as a fallback if the IPv4 address is mapped to another server. But if (HowTos)