SNMP (`snmp`)

Layer: Application and control
Header: variable length
Notes: Application protocols

Reached from

Lower layer	Selector	Value
`udp`	`dst_port` / `src_port`	161 (0x00a1)
`udp`	`dst_port` / `src_port`	162 (0x00a2)

Fields

Field	Type	Default	Auto	Description
`msg_tag`	`uint(8)`	`48`		BER tag octet (0x30 SEQUENCE, 0x02 INTEGER, 0x04 OCTET STRING).
`msg_length`	`uint(8)`		Length of the header and payload in octets (`-2`)	BER length of the SNMP message SEQUENCE (Auto; short form, below 128).
`version_tag`	`uint(8)`	`2`		BER tag octet (0x30 SEQUENCE, 0x02 INTEGER, 0x04 OCTET STRING).
`version_length`	`uint(8)`	`1`		BER length of the version INTEGER (1).
`version`	`enum(8)`	`1` (v2c)		SNMP version (0 = v1, 1 = v2c).
`community_tag`	`uint(8)`	`4`		BER tag octet (0x30 SEQUENCE, 0x02 INTEGER, 0x04 OCTET STRING).
`community_length`	`uint(8)`	`6`		BER length of the community string, in octets.
`community`	`bytes` — `community_length` octets	`70 75 62 6c 69 63`		Community string (e.g. “public”).

`version`

Value	Name
0 (0x00)	`v1`
1 (0x01)	`v2c`

Next layer

The next layer is selected by version; when the field is Auto the builder writes the value of the protocol stacked above.

Value	Protocol	Note
(any other value)	`snmp_pdu`

Constraints

Level	Rule
warning	`msg_tag` = 48
warning	header and payload at most 129 octets

Sample templates

snmp-get-request — templates/protocols/app/snmp-get-request.wpg.yaml
snmp-trap-v1 — templates/protocols/app/snmp-trap-v1.wpg.yaml