Post #2358501
2026-05-04 21:52 UTC
I absolutely agree IPv4-mapped addresses have no place in DNS.
The one place I have seen them used on the wire is as source address when some NAT64 gateway translates ICMP error messages into ICMPv6. I also think that’s wrong (they should be using their NAT64 prefix instead), but it’s not harmful in the same way that IPv4-mapped addresses in DNS are.
I can’t come up with any scenario where IPv4-mapped addresses on the wire would be a good idea.
Replies (1)
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@nygren@hachyderm.io 2026-05-05 02:55
@kasperd@westergaard.social @phils@chaos.social Yes, but there are lots of confused people who put IPv4-mapped IPv6 addresses in as AAAA records. It's way better than it used to be but @danwing@infosec.exchange has some reporting here which has history of this: https://www.employees.org/~dwing/aaaa-stats/ for example in 2011: https://www.employees.org/~dwing/aaaa-stats/ipv6-map.2011-09-26_0100.txt That practice seems to have ended years ago -- now it's mostly ULA.