The HP Color LaserJet 2840 Today I was presented a small problem: after adding a network printer HP Color LaserJet 2840 to a LAN I configured the client because stampassero that printer using the printing protocol CUPS . On all clients running Debian GNU / Linux iptables firewall protected. While the printer was located, was unable to start printing a document without first disabling the firewall.

Analysis and resolution of the problem have required only a few minutes! After having begun a `tail / var / log / messages I ran a test print:

#tail -f /var/log/messages
I got these videos immediately log lines generated by iptables:

Mar 18 12:34:53 localhost kernel: DROPPED IN= OUT=eth2 src=192.168.1.112 DST=192.168.1.138 LEN=78 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=UDP SPT=1700 DPT=161 LEN=58
Mar 18 12:34:53 localhost Officejet_6300_series?ip=192.168.1.138: INFO: open device failed; will retry in 30 seconds...

In other words, exchanging packets on UDP port 161 was blocked (in nerdese: Dropped) from the firewall. It is enough to add a rule to the firewall to allow the transit of UDP packets on that port to resolve the problem.