NAME

snmpd.conf — Simple Network Management Protocol daemon configuration file

DESCRIPTION

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

The snmpd.conf file is divided into the following main sections:

Macros

User-defined variables may be defined and used later, simplifying the configuration file.

Global Configuration

Global runtime settings for snmpd(8).

User Configuration

USM user definitions.

OID Configuration

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

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

GLOBAL CONFIGURATION

The following options can be set globally:

filter-pf-addresses (yes | no)

If set to yes, snmpd(8) will filter out the OPENBSD-PF-MIB::pfTblAddrTable tree. Addresses stored in PF tables will not be available, but CPU use will be reduced during bulk walks. The default is no.

filter-routes (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.

listen on [tcp | udp] address [port port] [read | write | notify]

Specify the local address snmpd(8) should listen on for incoming SNMP messages. The read flag specifies if the listen statement accepts get, getnext and bulkget requests. The write flag specifies if the listen statement accepts set requests and notify flags specifes if the listen statements accepts trapv1 and trapv2 requests. Multiple listen on statements are supported. The default protocol is udp. The default port is 161, unless the only listen flags contains notify which sets it to 162. If no flags are specified it defaults to “read write”, or notify when port is 162.

read-only community string

Specify the name of the read-only community. The default value is public.

read-write (community string | disabled)

Specify the name of the read-write community, or disallow writes completely. The default value is private.

seclevel (none | auth | enc)

Specify the lowest security level that snmpd(8) accepts:

none

Both authentication and encryption of messages is optional. This is the default value.

auth

Authentication of messages is mandatory. snmpd(8) will discard any messages that don't have a valid digest. Encryption of messages is optional.

enc

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.

system contact 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.

system description 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

system location string

Specify the string describing the location of the local system, typically a physical location. The default value is an empty string.

system name string

Specify the name of the local system, typically a fully-qualified domain name. The default value is the hostname of the local system.

system oid 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.

system services 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.

trap community string

Specify the name of the trap community. The default value is public.

trap handle 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). Traps will be accepted on all listen on UDP addresses.

trap receiver 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.

USER CONFIGURATION

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

user 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, hmac-sha1, hmac-sha224, hmac-sha256, hmac-sha384, or hmac-sha512. 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.

OID CONFIGURATION

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

oid 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.

FILES

/etc/snmpd.conf

Default location of the configuration file.

/etc/examples/snmpd.conf

Example configuration file.

EXAMPLES

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"

SEE ALSO

snmp(1), snmpd(8)

HISTORY

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

AUTHORS

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