[CentOS] Inconsistent printing on Centos 7

[Frank Cox]

On Fri, 29 Aug 2014 12:33:30 -0600
Frank Cox wrote:

> When the printers were hooked up to the Centos 7 machine, they weren't
> automatically "discovered" by the Centos 6 machines.

I note that Centos 7 uses cups-1.6.3-14 while Centos 6 uses cups-1.4.2-52

I found this email of interest:

https://lists.fedoraproject.org/pipermail/devel/2012-January/161306.html

As well as this article: http://lwn.net/Articles/485617/

Note that the email states as follows:

QUOTE:
One of the notable things that will be disappearing is CUPS Browsing.
This is currently the primary mechanism for CUPS-to-CUPS printer queue
discovery on Linux.  It works by having each CUPS server periodically
broadcast UDP packets on port 631 announcing its available queues.

This method of discovery is being dropped in favour of DNS-SD.  Support
for this has been upstream in CUPS for some time -- it's what CUPS uses
on Mac OS X -- but is not functional with Avahi. (For Fedora, I have
added patches to support Avahi.)

This means that once CUPS drops support for CUPS Browsing, automatic
CUPS queue discovery *will require Avahi* to be running on both the
server (i.e. the system hosting the CUPS queue) and the clients (i.e.
the systems wanting to print to it).
END OF QUOTE

Avahi is running on the Centos 6 computer that's now serving as the print server, as well as the Centos 7 machine.  mdns (port 5353udp) is open on both the print server and the Centos 7 client.

The remote printers still don't show up on the client unless I say "find network printer" with system-config-printer and then tell it specifically to scan the print server name.



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