The new SNMP network printer detection functionality in CUPS 1.2 sometimes exposes problems in vendor SNMP or IPP implementations. If you are experiencing long delays in loading the CUPS web interface administration page, or if you don’t see your printer listed, the following instructions will help you to diagnose those problems and/or provide important feedback to the CUPS developers so that we can correct problems and improve the SNMP backend in future releases.
If you don’t use “public” as your community name, create a text file called /etc/cups/snmp.conf and put the following line in it:
Community your community name
If you have more than one community name, list them all on separate lines.
If you don’t support SNMP v1 on your network, you are currently “out of luck”. That said, we will be adding v2, v2c, and v3 support in future CUPS releases once we have a handle on the actual requirements people have for such things. Please file or update an SNMP enhancement request (http://www.cups.org/str.php) with specific requirements you have - what you need supported, why you need it supported, and how you would like to see the functionality provided/exposed - so that we can do it “right” the first time.
The SNMP backend supports a debugging mode that is activated by running it from a shell prompt. If you are using Bash (/bin/bash), Bourne shell (/bin/sh), Korn shell (/bin/ksh), or Z shell (/bin/zsh), you can run the following command to get a verbose log of the SNMP backend:
CUPS_DEBUG_LEVEL=2 /usr/lib/cups/backend/snmp 2>&1 | tee snmp.log
For C shell (/bin/csh) and TCsh (/bin/tcsh), use the following command instead:
(setenv CUPS_DEBUG_LEVEL 2; /usr/lib/cups/backend/snmp) |& tee snmp.log
On MacOS X you’ll find the SNMP backend in /usr/libexec/cups/backend instead:
CUPS_DEBUG_LEVEL=2 /usr/libexec/cups/backend/snmp 2>&1 | tee snmp.log
The output will look something like this:
1 INFO: Using default SNMP Address @LOCAL
2 INFO: Using default SNMP Community public
3 DEBUG: Scanning for devices in "public" via "@LOCAL"...
4 DEBUG: 0.000 Sending 46 bytes to 192.168.2.255...
5 DEBUG: SEQUENCE 44 bytes
6 DEBUG: INTEGER 1 bytes 0
7 DEBUG: OCTET STRING 6 bytes "public"
8 DEBUG: Get-Request-PDU 31 bytes
9 DEBUG: INTEGER 4 bytes 1149539174
10 DEBUG: INTEGER 1 bytes 0
11 DEBUG: INTEGER 1 bytes 0
12 DEBUG: SEQUENCE 17 bytes
13 DEBUG: SEQUENCE 15 bytes
14 DEBUG: OID 11 bytes .1.3.6.1.2.1.25.3.2.1.2.1
15 DEBUG: NULL VALUE 0 bytes
16 DEBUG: 0.001 Received 55 bytes from 192.168.2.229...
17 DEBUG: community="public"
18 DEBUG: request-id=1149539174
19 DEBUG: error-status=0
20 DEBUG: SEQUENCE 53 bytes
21 DEBUG: INTEGER 1 bytes 0
22 DEBUG: OCTET STRING 6 bytes "public"
23 DEBUG: Get-Response-PDU 40 bytes
24 DEBUG: INTEGER 4 bytes 1149539174
25 DEBUG: INTEGER 1 bytes 0
26 DEBUG: INTEGER 1 bytes 0
27 DEBUG: SEQUENCE 26 bytes
28 DEBUG: SEQUENCE 24 bytes
29 DEBUG: OID 11 bytes .1.3.6.1.2.1.25.3.2.1.2.1
30 DEBUG: OID 9 bytes .1.3.6.1.2.1.25.3.1.5
31 DEBUG: add_cache(addr=0xbfffe170, addrname="192.168.2.229",
uri="(null)", id="(null)", make_and_model="(null)")
32 DEBUG: 0.002 Sending 46 bytes to 192.168.2.229...
33 DEBUG: SEQUENCE 44 bytes
34 DEBUG: INTEGER 1 bytes 0
35 DEBUG: OCTET STRING 6 bytes "public"
36 DEBUG: Get-Request-PDU 31 bytes
37 DEBUG: INTEGER 4 bytes 1149539175
38 DEBUG: INTEGER 1 bytes 0
39 DEBUG: INTEGER 1 bytes 0
40 DEBUG: SEQUENCE 17 bytes
41 DEBUG: SEQUENCE 15 bytes
42 DEBUG: OID 11 bytes .1.3.6.1.2.1.25.3.2.1.3.1
43 DEBUG: NULL VALUE 0 bytes
44 DEBUG: 0.003 Received 69 bytes from 192.168.2.229...
45 DEBUG: community="public"
46 DEBUG: request-id=1149539175
47 DEBUG: error-status=0
48 DEBUG: SEQUENCE 67 bytes
49 DEBUG: INTEGER 1 bytes 0
50 DEBUG: OCTET STRING 6 bytes "public"
51 DEBUG: Get-Response-PDU 54 bytes
52 DEBUG: INTEGER 4 bytes 1149539175
53 DEBUG: INTEGER 1 bytes 0
54 DEBUG: INTEGER 1 bytes 0
55 DEBUG: SEQUENCE 40 bytes
56 DEBUG: SEQUENCE 38 bytes
57 DEBUG: OID 11 bytes .1.3.6.1.2.1.25.3.2.1.3.1
58 DEBUG: OCTET STRING 23 bytes "HP LaserJet 4000
Series"
59 DEBUG: 1.001 Probing 192.168.2.229...
60 DEBUG: 1.001 Trying socket://192.168.2.229:9100...
61 DEBUG: 192.168.2.229 supports AppSocket!
62 DEBUG: 1.002 Scan complete!
63 network socket://192.168.2.229 "HP LaserJet 4000 Series"
"HP LaserJet 4000 Series 192.168.2.229" ""
The first two lines are just informational and let you know that the default community name and address are being used. Lines 3-15 contain the initial SNMP query for the device type OID (.1.3.6.1.2.1.25.3.2.1.2.1) from the Host MIB.
Lines 16-31 show the response we got from an HP LaserJet 4000 network printer. At this point we discover that it is a printer device and then send another SNMP query (lines 32-43) for the device description OID (.1.3.6.1.2.1.25.3.2.1.3.1) from the Host MIB as well.
Lines 44-58 show the response to the device description query, which tells us that this is an HP LaserJet 4000 Series printer.
On line 59 we start our active connection probe and discover that this print server supports the AppSocket (JetDirect) protocol on port 9100.
Finally, line 63 shows the device information line for the print server that is sent to CUPS.
If you don’t see your printer listed, or the wrong information is listed, then you need to gather more information on the printer. The easiest way to do this is to run the snmpwalk command:
snmpwalk -Cc -v 1 -c public ip-address | tee snmpwalk.log
where “ip-address” is the IP address of the printer or print server. You should see a lot of values stream by - the ones you want to see are:
HOST-RESOURCES-MIB::hrDeviceType.1 = OID: HOST-RESOURCES-TYPES::hrDevicePrinter HOST-RESOURCES-MIB::hrDeviceDescr.1 = STRING: HP LaserJet 4000 Series
The hrDeviceType line should show hrDevicePrinter; if not, then your printer or print server doesn’t identify itself as a printer. The hrDeviceDescr line should provide a human-readable string for the make and model of the printer, although in some cases you’ll just see something less useful like “Axis OfficeBASIC Parallel Print Server”.
Once you have collected the snmpwalk output, you should go to the CUPS Bugs & Features page (http://www.cups.org/str.php) to submit a feature request to support your printer or print server. Be sure to attach those two log files you created - they will help us to identify the SNMP values we need to look for.