I had a very weird issue on a new Debian installation where the Cups print server gui was very slow to respond and the printers were also slow to print. When you attempt to print a page there was a 4/5 second delay before the print job would be sent to the printer.
After much investigation I have since resolved the issue which relates to IPV6 even though there was no IPV6 entries for this server.
I had set IPV6 IP Tables firewall rules to just block all connections in and out.
The fix was to “Allow All” for the IPV6 loopback device which seemed to resolve the issue and then add a local entry for IPV6 into the hosts file.
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -i lo -j ACCEPT
The issue seems very odd since Cups was mean’t to be communicating over IPV4, There were no host entries for IPV6 either just IPV4 but this was definitely the fix I required.
Hopefully someone else finds this post as I struggled to find resources on this issue!