I have a CentOS stream 8 system (C8) which runs its own internal name server (BIND 9). In the past, it used an external name server on another machine but that server has been stopped. The resolv.conf file on C8 has been modified to remove the reference to the old server and NetworkManager has been restarted. However, CUPS and other programs on C8 continue to send queries to the old server, all of which eventually time out (of course). The bogus queries to the old server are answered with ICMP destination/port unreachable, confirming that the old name server is not running. But these bogus queries take time and the delays are very annoying.
I've also restarted CUPS without effect. There are no references to the old server in /etc/named.conf, but there are references to the subnet it was on as there are other machines there that need to use the new name server. I haven't yet rebooted C8 but I'm prepared if necessary.
Is there something else I should do before rebooting C8? Is that even likely to solve the problem?