I interpret the --no-dns-cache man documentation to suggest this behavior is intentional. Here's the relevant excerpt.
--no-dns-cache Turn off caching of DNS lookups. Normally, Wget remembers the IP addresses it looked up from DNS so it doesn’t have to repeatedly contact the DNS server for the same (typically small) set of hosts it retrieves from. This cache exists in memory only; a new Wget run will contact DNS again. However, it has been reported that in some situations it is not desirable to cache host names, even for the duration of a short-running application like Wget. With this option Wget issues a new DNS lookup (more precisely, a new call to "gethostbyname" or "getaddrinfo") each time it makes a new connection. [snip] -- wget doesn't redo DNS lookup https://launchpad.net/bugs/84104 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
