iptables is converting the IP into a domain
Solution 1:
This is normal, nothing to worry about move on and you should read the documentation.
You didn't specify -n
-n, --numeric Numeric output. IP addresses and port numbers will be printed in numeric format. By default, the program will try to display them as host names, network names, or services (whenever applicable).
so iptables tries it's best to provide a meaningful name. If you do a reverse lookup on 77.0.0.0 the result will look familiar.
dig -x 77.0.0.0 +short
x4d000000.dyn.telefonica.de.