Enable SNMP Traps

Description

SNMP traps are information sent using the SNMP protocol from monitored equipment to a poller server. This information contains multiple Attributes including:

• Address of the equipment sending the information.
• The root OID (Object Identifier) corresponding to the identifier of the message received.
• The message sent via the SNMP trap which corresponds to a set of settings (1 to N).

In order to be able to interpret the event received the Network supervisor server needs to possess in its configuration the necessary elements to translate the event. For this it must have a database containing the OID and the descriptions, this is what is called MIB files. There are two types of MIB:

• Standard MIBs which use standardized OIDs and which are implemented by numerous manufacturers on their equipment.
• MIB manufacturers who are specific to each one and often to each equipment model.

MIB manufacturers can be retrieved from the equipment. Centreon allows us to store the definition of SNMP traps in its MariaDB database. The traps can subsequently be linked to passive services via the Relations tab of the definition of a service.

Architecture

SNMP trap processing by the central server

The processing of an SNMP trap is as follows:

1. snmptrapd is the service enabling the retrieval of SNMP traps sent by the equipment (by default it listens on port UDP 162).
2. Once the SNMP trap has been received, it is sent to the ‘centreontrapdforward’ script which writes the information received in a buffer folder (by default /var/spool/centreontrapd/).
3. The ‘centreontrapd’ service reads the information received in the buffer folder and interprets the traps received checking, in the centreon database, the actions necessary to process these events.
4. The ‘centreontrapd’ service transmits the information to the scheduler or the ‘gorgoned’ service (to send the information to a remote scheduler) which changes the status and the information associated with service to which the SNMP trap is linked.

SNMP trap processing by a poller server

To keep a copy of the configuration of the SNMP traps on each satellite server, an SQLite database is charged with keeping the information of the traps contained in the MariaDB database cached. This SQLite database is automatically generated by the central server.

The processing of an SNMP trap is as follows:

1. snmptrapd is the service used to retrieve the SNMP traps sent by the equipment (by default it listens on port UDP 162).
2. Once the SNMP trap is received, it is sent to the ‘centreontrapdforward’ script which writes the information received in a buffer folder (by default /var/spool/centreontrapd/).
3. The ‘centreontrapd’ service reads the information received in the buffer folder and interprets the various traps received checking in the SQLite database the actions to be taken to process the traps received.
4. The ‘centreontrapd’ service transmits the information to the scheduler which changes the status and the information associated with the service to which the SNMP trap is linked.

The Centreon Gorgone process is responsible to copy the SQLite base on the remote poller.

Successive actions by the centreontrapd process

Successive actions by the centreontrapd process are:

Configuring services

Snmptrapd

To call the ‘centreontrapdfoward’ script, the file /etc/snmp/snmptrapd.conf must contain the following lines:

disableAuthorization yes
traphandle default su -l centreon -c "/usr/share/centreon/bin/centreontrapdforward"

You can optimize the performances of snmptrapd by using the following options:

• -On don’t try to convert the OIDs
• -t don’t log the traps to the syslog server
• -n don’t try to convert the IP addresses into host names

These options can be changed in the file /etc/sysconfig/snmptrapd:

OPTIONS="-On -d -t -n -p /var/run/snmptrapd.pid"

centreontrapdforward

To change the buffer folder towards which the information will be written, change the configuration file /etc/centreon/centreontrapd.pm:

our %centreontrapd_config = (
    spool_directory => '/var/spool/centreontrapd/',
);

1;

You can also map the folder in the RAM, by adding the following line in the file /etc/fstab:

tmpfs /var/spool/centreontrapd      tmpfs defaults,size=512m 0 0

centreontrapd

Two configuration files existent in centreontrapd:

• /etc/centreon/conf.pm contains the connection information to the MariaDB database
• /etc/centreon/centreontrapd.pm contains the configuration of the centreontrapd service

Configuration of the service

In the file /etc/centreon/centreontrapd.pm we advise changing three settings only (if necessary):

• If the mode option is defined in 1 centreontrapd functions on a satellite server, otherwise it functions on a central server (centreon).
• The centreon_user option can be used to change the user executing the actions.
• The spool_directory option can be used to change the buffer folder to be read (if you have changed it in the ‘centreontrapdforward’ configuration file).

Here is an example of possible configuration of the file /etc/centreon/centreontrapd.pm (the configuration file can be changed with ‘-config-extra = xxx’):

our %centreontrapd_config = (
    # Time in seconds before killing not gently sub process
    timeout_end => 30,
    spool_directory => "/var/spool/centreontrapd/",
    # Delay between spool directory check new files
    sleep => 2,
    # 1 = use the time that the trap was processed by centreontrapdforward
    use_trap_time => 1,
    net_snmp_perl_enable => 1,
    mibs_environment => '',
    remove_backslash_from_quotes => 1,
    dns_enable => 0,
    # Separator for arguments substitution
    separator => ' ',
    strip_domain => 0,
    strip_domain_list => [],
    duplicate_trap_window => 1,
    date_format => "",
    time_format => "",
    date_time_format => "",
    # Time in seconds before cache reload
    cache_unknown_traps_retention => 600,
    # 0 = central, 1 = poller
    mode => 0,
    cmd_timeout => 10,
    centreon_user => "centreon",
    # 0 => skip if MariaDB error | 1 => don't skip (block) if MariaDB error (and keep order)
    policy_trap => 1,
    # Log DB
    log_trap_db => 0,
    log_transaction_request_max => 500,
    log_transaction_timeout => 10,
    log_purge_time => 600
);

1;

Configuring the database connection

On Centreon Central server, edit the /etc/centreon/conf.pm file:

$centreon_config = {
    VarLib => "/var/lib/centreon",
    CentreonDir => "/usr/share/centreon/",
    "centreon_db" => "centreon",
    "centstorage_db" => "centreon_storage",
    "db_host" => "localhost:3306",
    "db_user" => "centreon",
    "db_passwd" => "centreon"
};

1;

On a poller, edit the /etc/centreon/centreontrapd.pm file:

our %centreontrapd_config = (
    ...
    "centreon_db" => "dbname=/etc/snmp/centreon_traps/centreontrapd.sdb",
    "centstorage_db" => "dbname=/etc/snmp/centreon_traps/centreontrapd.sdb",
    "db_host" => "",
    "db_user" => "",
    "db_passwd" => "",
    "db_type" => 'SQLite',
    ...
);

1;