My local nameserver root zone file is outdated. It has no information about IPv6 and a root server recently changed its IP address.
How do I update my root hints data file on a Linux server?
You can download it:
wget --user=ftp --password=ftp ftp://ftp.rs.internic.net/domain/db.cache -O /etc/bind/db.root
Or you can generate it yourself:
dig +bufsize=1200 +norec NS . @a.root-servers.net | egrep -v ';|^$' | sort > /etc/bind/db.root
After all, refresh the name server.