dayvee@laptop:~$ nslookup háčkyčárky.cz Server: 192.168.1.1 Address: 192.168.1.1#53 ** server can't find háčkyčárky.cz: NXDOMAIN dayvee@laptop:~$ nslookup xn--hkyrky-ptac70bc.cz Server: 192.168.1.1 Address: 192.168.1.1#53 Non-authoritative answer: Name: xn--hkyrky-ptac70bc.cz Address: 217.31.204.66 dayvee@laptop:~$ ping háčkyčárky.cz ping: unknown host háčkyčárky.cz dayvee@laptop:~$ ping xn--hkyrky-ptac70bc.cz PING xn--hkyrky-ptac70bc.cz (217.31.204.66) 56(84) bytes of data. 64 bytes from public.nic.cz (217.31.204.66): icmp_seq=1 ttl=59 time=15.1 ms... atd :-)
IDN SUPPORTTudíž zjevně váš nslookup a ping není zkompilovaný s podporou IDN. Otázka, kterou zbývá odpovědět, a myslím si, že odpověď na ni je NE, je: Má nslookup a ping (tedy vlastně stub resolver v libc6) podporu pro IDN?
If dig has been built with IDN (internationalized domain name) support, it can accept and display non-ASCII domain names. dig appropriately converts character encoding of domain name before sending a request to DNS server or displaying a reply from the server. If you’d like to turn off the IDN support for some reason, defines the IDN_DISABLE environment variable. The IDN support is disabled if the variable is set when dig runs.