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SNMPD.CONF(5) File Formats Manual SNMPD.CONF(5)

snmpd.conf — Simple Network Management Protocol daemon configuration file

snmpd.conf is the configuration file for the snmpd(8) daemon.

The snmpd.conf file is divided into three main sections:

User-defined variables may be defined and used later, simplifying the configuration file.
Global runtime settings for snmpd(8).
USM user definitions.
Custom configuration of SNMP object identifiers and values.

The current line can be extended over multiple lines using a backslash (‘\’). Comments can be put anywhere in the file using a hash mark (‘#’), and extend to the end of the current line. Care should be taken when commenting out multi-line text: the comment is effective until the end of the entire block.

Argument names not beginning with a letter, digit, or underscore must be quoted.

Additional configuration files can be included with the include keyword, for example:

include "/etc/snmpd.conf.local"

Macros can be defined that will later be expanded in context. Macro names must start with a letter, digit, or underscore, and may contain any of those characters. Macro names may not be reserved words (for example, community, system, or oid). Macros are not expanded inside quotes.

For example:

ext_addr="192.168.0.1"
listen on $ext_addr

The following options can be set globally:

(yes | no)
If set to yes, ask the kernel to filter route update messages on the routing socket. Routing table information will not be available, but CPU use will be reduced during bulk updates. The default is no.
address
Specify the local address snmpd(8) should listen on for incoming SNMP messages.
string
Specify the name of the read-only community. The default value is public.
(community string | disabled)
Specify the name of the read-write community, or disallow writes completely. The default value is private.
(none | auth | enc)
Specify the lowest security level that snmpd(8) accepts:
Both authentication and encryption of messages is optional. This is the default value.
Authentication of messages is mandatory. snmpd(8) will discard any messages that don't have a valid digest. Encryption of messages is optional.
Messages must be encrypted and must have a valid digest for authentication. Otherwise they will be discarded.

If the chosen value is different from none snmpd(8) will accept only SNMPv3 requests since older versions neither support authentication nor encryption.

"path" [restricted | agentx]
Create a control socket at path. If restricted is specified, a restricted control socket will be created. If agentx is specified, a socket which speaks the AgentX protocol will be created. Multiple restricted and agentx sockets may be created. By default /var/run/snmpd.sock is created and no other sockets are created.
string
Specify the name or description of the system contact, typically a name or an email address. The default value is root@hostname using the hostname of the local machine.
string
Specify a description of the local system. The default value is the operating system identification as printed by the uname(1) command using the -a flag: 
OpenBSD myhost.example.com 4.2 GENERIC#595 i386
string
Specify the string describing the location of the local system, typically a physical location. The default value is an empty string.
string
Specify the name of the local system, typically a fully-qualified domain name. The default value is the hostname of the local system.
oid-string
Specify the authoritative identification of the local system. The default value is 1.3.6.1.4.1.30155.23.1 (iso.org.dod.internet.private.enterprises.openbsd.23.1) identifying a common OpenBSD system.
number
Specify a magic value which indicates the set of services that the local system may provide. Refer to the sysServices description in the SNMP MIB for details.
string
Specify the name of the trap community. The default value is public.
oid "command"
Execute command upon receipt of an SNMP trap that begins with a prefix of oid. Alternately, the string "default" may be used, in which case the prefix used is 1.3. The invoked command will receive the following information about the trap on standard input, one per line, in this order: the resolved hostname of the host sending the trap, the IP address of the host sending the trap, and any variable bindings contained in the trap (the OID followed by the value, separated by a single space).
string [oid oid-string] [community string] [source-address address]
Specify the address or FQDN of a remote trap receiver for outgoing traps sent by snmpd(8). This option may be specified multiple times. The daemon will send outgoing traps using the revised SNMPv2 format and the configured trap community. The default community is specified by the global trap community option. The IPv4 or IPv6 source address of the traps can be enforced using source-address.

Users for the SNMP User-based Security Model (USM, RFC 3414) must be defined in the configuration file:

name [authkey key auth hmac] [enckey key enc cipher]
Defines a known user. The authkey keyword is required to specify the digest key used to authenticate messages. If this keyword is omitted then authentication is disabled for this user account. Optionally the HMAC algorithm used for authentication can be specified. hmac must be either hmac-md5 or hmac-sha1. If omitted the default is hmac-sha1.

With enckey the encryption key used to encrypt and decrypt messages for privacy is defined. Without an enckey specification the user account will neither accept encrypted incoming messages nor will it encrypt outgoing messages. The enc algorithm can be either des or aes and defaults to des.

Any user account that has encryption enabled requires authentication to be enabled too.

It is possible to specify user-defined OIDs in the configuration file:

oid-string name name [read-only | read-write] [type] value
Return the specified value to the client for this OID. The read-write option may allow the client to override it, and the type is either string or integer.

/etc/snmpd.conf
Default location of the configuration file.

The following example will tell snmpd(8) to listen on localhost, override the default system OID, set the magic services value and provides some custom OID values:

listen on 127.0.0.1

system oid 1.3.6.1.4.1.30155.23.2
system services 74

oid 1.3.6.1.4.1.30155.42.1 name myName read-only string "humppa"
oid 1.3.6.1.4.1.30155.42.2 name myStatus read-only integer 1

The next example will enforce SNMPv3 with authenticated and encrypted communication and the user-based security model. The configuration defines two users, the first one is using the aes encryption algorithm and the second one the default des algorithm.

seclevel enc

user "hans" authkey "password123" enc aes enckey "321drowssap"
user "sophie" authkey "password456" enckey "654drowssap"

snmpctl(8), snmpd(8)

The snmpd.conf file format first appeared in OpenBSD 4.3.

The snmpd(8) program was written by Reyk Floeter <reyk@openbsd.org>.

November 9, 2016 OpenBSD-6.1