collectd-snmp - Documentation of collectd's "snmp plugin"
Values "IF-MIB::ifInOctets" "IF-MIB::ifOutOctets"
Collect "std_traffic" "hr_users"
The "snmp plugin" queries other hosts using SNMP, the simple network
management protocol, and translates the value it receives to collectd's
internal format and dispatches them. Depending on the write plugins you have
loaded they may be written to disk or submitted to another instance or
whatever you configured.
Because querying a host via SNMP may produce a timeout multiple threads are used
to query hosts in parallel. Depending on the number of hosts between one and
ten threads are used.
Since the aim of the "snmp plugin" is to provide a generic interface
to SNMP, it's configuration is not trivial and may take some time.
Since the "Net-SNMP" library is used you can use all the environment
variables that are interpreted by that package. See snmpcmd
(1) for more
There are two types of blocks that can be contained in the
"<Plugin snmp>" block: Data
block defines a list of values or a table of values that are to
be queried. The following options can be set:
- Type type
- collectd's type that is to be used, e. g.
"if_octets" for interface traffic or "users" for a
user count. The types are read from the TypesDB (see
collectd.conf(5)), so you may want to check for which types are
defined. See types.db(5) for a description of the format of this
- Table true|false
- Define if this is a single list of values or a table of
values. The difference is the following:
When Table is set to false, the OIDs given to Values
(see below) are queried using the "GET" SNMP command (see
snmpget(1)) and transmitted to collectd. One value list is
dispatched and, eventually, one file will be written.
When Table is set to true, the OIDs given to Values
(see below) are queried using the "GETNEXT" SNMP command until
the subtree is left. After all the lists (think: all columns of the table)
have been read several values sets will be dispatches and,
eventually, several files will be written. If you configure a Type
(see above) which needs more than one data source (for example
"if_octets" which needs "rx" and "tx") you
will need to specify more than one (two, in the example case) OIDs with
the Values option. This has nothing to do with the Table
For example, if you want to query the number of users on a system, you can
use "HOST-RESOURCES-MIB::hrSystemNumUsers.0". This is one value
and belongs to one value list, therefore Table must be set to
false. Please note that, in this case, you have to include the
sequence number (zero in this case) in the OID.
Counter example: If you want to query the interface table provided by the
"IF-MIB", e. g. the bytes transmitted. There are
potentially many interfaces, so you will want to set Table to
true. Because the "if_octets" type needs two values,
received and transmitted bytes, you need to specify two OIDs in the
Values setting, in this case likely
"IF-MIB::ifHCInOctets" and "IF-MIB::ifHCOutOctets".
But, this is because of the Type setting, not the Table
Since the semantic of Instance and Values depends on this
setting you need to set it before setting them. Doing vice verse will
result in undefined behavior.
- Instance Instance
- Sets the type-instance of the values that are dispatched.
The meaning of this setting depends on whether Table is set to
true or false:
If Table is set to true, Instance is interpreted as an
SNMP-prefix that will return a list of values. Those values are then used
as the actual type-instance. An example would be the
"IF-MIB::ifDescr" subtree. variables(5) from the SNMP
distribution describes the format of OIDs.
If Table is set to true and Instance is omitted, then
"SUBID" will be used as the instance.
If Table is set to false the actual string configured for
Instance is copied into the value-list. In this case
Instance may be empty, i. e. "".
- InstancePrefix String
- If Table is set to true, you may feel the
need to add something to the instance of the files. If set, String
is prepended to the instance as determined by querying the agent. When
Table is set to false this option has no effect.
The "UPS-MIB" is an example where you need this setting: It has
voltages of the inlets, outlets and the battery of an UPS. However, it
doesn't provide a descriptive column for these voltages. In this case
having 1, 2, ... as instances is not enough, because the inlet
voltages and outlet voltages may both have the subids 1, 2, ... You
can use this setting to distinguish between the different voltages.
- Values OID [OID ...]
- Configures the values to be queried from the SNMP host. The
meaning slightly changes with the Table setting.
variables(5) from the SNMP distribution describes the format of
If Table is set to true, each OID must be the prefix of
all the values to query, e. g. "IF-MIB::ifInOctets" for
all the counters of incoming traffic. This subtree is walked (using
"GETNEXT") until a value from outside the subtree is returned.
If Table is set to false, each OID must be the OID of
exactly one value, e. g. "IF-MIB::ifInOctets.3" for the
third counter of incoming traffic.
- Scale Value
- The gauge-values returned by the SNMP-agent are multiplied
by Value. This is useful when values are transferred as a fixed
point real number. For example, thermometers may transfer 243 but
actually mean 24.3, so you can specify a scale value of 0.1
to correct this. The default value is, of course, 1.0.
This value is not applied to counter-values.
- Shift Value
- Value is added to gauge-values returned by the
SNMP-agent after they have been multiplied by any Scale value. If,
for example, a thermometer returns degrees Kelvin you could specify a
shift of 273.15 here to store values in degrees Celsius. The
default value is, of course, 0.0.
This value is not applied to counter-values.
- Ignore Value [, Value ...]
- The ignore values allows one to ignore Instances based on
their name and the patterns specified by the various values you've
entered. The match is a glob-type shell matching.
- InvertMatch true|false(default)
- The invertmatch value should be use in combination of the
Ignore option. It changes the behaviour of the Ignore option, from a
blacklist behaviour when InvertMatch is set to false, to a whitelist when
specified to true.
block defines which hosts to query, which SNMP community and
version to use and which of the defined Data
The argument passed to the Host
block is used as the hostname in the data
stored by collectd.
- Address IP-Address|Hostname
- Set the address to connect to.
- Version 1|2|3
- Set the SNMP version to use. When giving 2 version
"2c" is actually used.
- Community Community
- Pass Community to the host. (Ignored for
- Username Username
- Sets the Username to use for SNMPv3 security.
- Selects the security level for SNMPv3 security.
- Context Context
- Sets the Context for SNMPv3 security.
- AuthProtocol MD5|SHA
- Selects the authentication protocol for SNMPv3
- AuthPassphrase Passphrase
- Sets the authentication passphrase for SNMPv3
- PrivacyProtocol AES|DES
- Selects the privacy (encryption) protocol for SNMPv3
- PrivacyPassphrase Passphrase
- Sets the privacy (encryption) passphrase for SNMPv3
- Collect Data [Data ...]
- Defines which values to collect. Data refers to one
of the Data block above. Since the config file is read top-down you
need to define the data before using it here.
- Interval Seconds
- Collect data from this host every Seconds seconds.
This option is meant for devices with not much CPU power, e. g.
network equipment such as switches, embedded devices, rack monitoring
systems and so on. Since the Step of generated RRD files depends on
this setting it's wise to select a reasonable value once and never change
Florian Forster <email@example.com> Michael Pilat