Configure CUPS in RHEL to use ephemeral ports instead of reserved ports

Solution Verified - Updated -

Issue

  • When we have many users printing at once, CUPS is very slow. In the file /var/log/cups/error_log we repeatedly find the following:

    E [09/Jul/2013:10:06:00 +0200] [Job 865106] Unable to reserve port: Resource temporarily unavailable

  • Our firewall blocks connections initiated from low-numbered TCP ports (port numberss less than 1024). This is blocking CUPS outgoing LPD (Line Printer Deamon) protocol connections to our printers. What can we do?

  • We are experiencing issues when the source port of an LPD connection is 1021. Is there a way to configure CUPS to not use reserved ports?

Environment

  • Red Hat Enterprise Linux (RHEL), all versions
  • Common Unix Printing System (CUPS), all versions

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