On Fri, Dec 9, 2022, at 12:57, Stuart Henderson wrote: > On 2022-12-09, Byron Klippert <byronklipp...@ml1.net> wrote: >> Hello, >> >> I get an snmp protocol error response when attempting to `snmp get` certain >> OIDs on various devices. However `tcpdump` shows that the device is actually >> responding with the anticipated result but it appears snmp isn't able to >> parse the response correctly? Any suggestions on how to troubleshoot further >> are welcome. >> >> >> I'm requesting the mntrFreq OID which is formatted as such: >> Name: mntrFreq >> OID: .1.3.6.1.4.1.35833.12.3.1 >> MIB: DB7000-MIB >> Syntax: INTEGER32 (87100..108100) >> Access: read-only >> Status: current >> DefVal: >> Indexes: >> Descr: "mntr Freq" > > btw, the information in the mib file doesn't necessarily correspond > to what the device actually sends, "snmp get" doesn't care about the > mib file at all, just whether the pdu is correctly formatted.
Yup, understood. I've seen a few half-baked snmp implementations in the wild to know the MIB docs are often only suggestions as to how devices actually respond. > >> imac:/home/admin $ snmp get -v 2c -r 0 -c *redacted* udp:paint-receiver:161 >> .1.3.6.1.4.1.35833.12.3.1.0 >> snmp: get: Protocol error >> >> imac:/home/admin $ doas tcpdump host paint-receiver >> tcpdump: listening on bge0, link-type EN10MB >> 10:10:02.804614 192.168.0.4.21246 > paint-receiver.snmp: C=*redacted* >> GetRequest(32) E:35833.12.3.1.0 >> 10:10:03.231863 paint-receiver.snmp > 192.168.0.4.21246: C=*redacted* >> GetResponse(40) E:35833.12.3.1.0=103500 > > It might be useful to use -X to do a hexdump (and maybe -s1500 to make > sure you get full packets); if you need to redact the snmp community > (although it probably doesn't really matter all that much seeing as > it's on a private lan address) make sure you get the hex digits too > > That way we can get a better idea of what's actually sent on the wire > > > -- > Please keep replies on the mailing list. imac:/home/admin $ snmp get -v 2c -r 0 -c *redacted* udp:paint-receiver:161 .1.3.6.1.4.1.35833.12.3.1.0 snmp: get: Protocol error imac:/home/admin $ clear; doas tcpdump -X -s1500 host paint-receiver tcpdump: listening on bge0, link-type EN10MB 13:23:16.478673 192.168.0.4.11162 > paint-receiver.snmp: C=*redacted* GetRequest(32) E:35833.12.3.1.0 0000: 4500 004d ce0a 0000 4011 0000 c0a8 0004 E..M....@....... 0010: c0a8 050c 2b9a 00a1 0039 aac2 302f 0201 ....+....9..0/.. 0020: 0104 082a 2a2a 2a2a 2a2a 2aa0 2002 0428 ...********. ..( 0030: f7c4 fb02 0100 0201 0030 1230 1006 0c2b .........0.0...+ 0040: 0601 0401 8297 790c 0301 0005 00 ......y...... 13:23:17.366836 paint-receiver.snmp > 192.168.0.4.11162: C=*redacted* GetResponse(40) E:35833.12.3.1.0=103500 0000: 4500 0059 f938 0000 fd11 3dfa c0a8 050c E..Y.8....=..... 0010: c0a8 0004 00a1 2b9a 0045 c089 3082 0039 ......+..E..0..9 0020: 0201 0104 082a 2a2a 2a2a 2a2a 2aa2 8200 .....********... 0030: 2802 0428 f7c4 fb02 0100 0201 0030 8200 (..(.........0.. 0040: 1830 8200 1406 0c2b 0601 0401 8297 790c .0.....+......y. 0050: 0301 0002 0400 0194 4c ........L And here's the OID that responds correctly... imac:/home/admin $ snmp get -v 2c -r 0 -c *redacted* udp:paint-receiver:161 .1.3.6.1.4.1.35833.12.2.10.1.0 enterprises.35833.12.2.10.1.0 = STRING: DB7000: Paint Mt imac:/home/admin $ clear; doas tcpdump -X -s1500 host paint-receiver tcpdump: listening on bge0, link-type EN10MB 13:32:08.168829 192.168.0.4.44771 > paint-receiver.snmp: C=*redacted* GetRequest(33) E:35833.12.2.10.1.0 0000: 4500 004e 36ee 0000 4011 0000 c0a8 0004 E..N6...@....... 0010: c0a8 050c aee3 00a1 003a caeb 3030 0201 .........:..00.. 0020: 0104 082a 2a2a 2a2a 2a2a 2aa0 2102 0459 ...********.!..Y 0030: f71a 4f02 0100 0201 0030 1330 1106 0d2b ..O......0.0...+ 0040: 0601 0401 8297 790c 020a 0100 0500 ......y....... 13:32:08.988687 paint-receiver.snmp > 192.168.0.4.44771: C=*redacted* GetResponse(53) E:35833.12.2.10.1.0="DB7000: Paint Mt" 0000: 4500 0066 f967 0000 fd11 3dbe c0a8 050c E..f.g....=..... 0010: c0a8 0004 00a1 aee3 0052 ade8 3082 0046 .........R..0..F 0020: 0201 0104 082a 2a2a 2a2a 2a2a 2aa2 8200 .....********... 0030: 3502 0459 f71a 4f02 0100 0201 0030 8200 5..Y..O......0.. 0040: 2530 8200 2106 0d2b 0601 0401 8297 790c %0..!..+......y. 0050: 020a 0100 0410 4442 3730 3030 3a20 5061 ......DB7000: Pa 0060: 696e 7420 4d74 int Mt -- Byron Klippert byronklipp...@ml1.net c. 867-334-5179
