SNMP Interface Poller

Meridian can monitor the status of an SNMP interface that is not directly monitored by a Service Assurance monitor.

The SNMP interface poller is a separate service that uses a node interface, typically a management interface, to get administration and operational status for other interfaces present on the device. On a configurable time interval, a SNMP GET request is made for two specific objects in an ifEntry of the ifTable defined in the IF-MIB:

ifAdminStatus OBJECT-TYPE
              SYNTAX  INTEGER {
                          up(1),       -- ready to pass packets
                          down(2),
                          testing(3)   -- in some test mode
                      }
              ACCESS  read-write
              STATUS  current
              DESCRIPTION
                      "The desired state of the interface.  The testing(3) state
                      indicates that no operational packets can be passed. When a
                      managed system initializes, all interfaces start with
                      ifAdminStatus in the down(2) state.  As a result of either
                      explicit management action or per configuration information
                      retained by the managed system, ifAdminStatus is then
                      changed to either the up(1) or testing(3) states (or remains
                      in the down(2) state)."
              ::= { ifEntry 7 }

ifOperStatus OBJECT-TYPE
              SYNTAX  INTEGER {
                          up(1),        -- ready to pass packets
                          down(2),
                          testing(3),   -- in some test mode
                          unknown(4),   -- status can not be determined
                                        -- for some reason.
                          dormant(5),
                          notPresent(6),    -- some component is missing
                          lowerLayerDown(7) -- down due to state of
                                            -- lower-layer interface(s)
                      }
              ACCESS  read-only
              STATUS  current
              DESCRIPTION
                      "The current operational state of the interface.  The
                      testing(3) state indicates that no operational packets can
                      be passed.  If ifAdminStatus is down(2) then ifOperStatus
                      should be down(2).  If ifAdminStatus is changed to up(1)
                      then ifOperStatus should change to up(1) if the interface is
                      ready to transmit and receive network traffic; it should
                      change to dormant(5) if the interface is waiting for
                      external actions (such as a serial line waiting for an
                      incoming connection); it should remain in the down(2) state
                      if and only if there is a fault that prevents it from going
                      to the up(1) state; it should remain in the notPresent(6)
                      state if the interface has missing (typically, hardware)
                      components."
              ::= { ifEntry 8 }

After retrieving these values the service will:

Update the values of ifAdminStatus and ifOperStatus of the polled interfaces in the database. This column is normally updated only when an import of a Provisiond requisition takes place.
Send events when the state of a polled interface changes state. The UEIs of these events are:
- uei.opennms.org/nodes/snmp/interfaceAdminDown
- uei.opennms.org/nodes/snmp/interfaceAdminUp
- uei.opennms.org/nodes/snmp/interfaceOperDown
- uei.opennms.org/nodes/snmp/interfaceOperUp
- uei.opennms.org/nodes/snmp/interfaceOperTesting
- uei.opennms.org/nodes/snmp/interfaceOperUnknown
- uei.opennms.org/nodes/snmp/interfaceOperDormant
- uei.opennms.org/nodes/snmp/interfaceOperNotPresent
- uei.opennms.org/nodes/snmp/interfaceOperLowerLayerDown

The appropriate event will be sent whenever:

a polled interface’s ifAdminStatus is up and ifOperStatus is in a down state at startup
ifAdminStatus is in an up state and ifOperStatus transitions to a down state from a not down state
ifAdminStatus is in an up state and ifOperStatus transitions to an up state from a not up state
ifAdminStatus transitions to a down state from a not down state
ifAdminStatus transitions to an up state from a not up state

It is possible to configure the service to treat additional values of ifOperStatus as logically up or down. In the event that this configuration option is used and ifOperStatus transitions to a state configured as a down value that is not literally down(2), both the uei.opennms.org/nodes/snmp/interfaceOperDown event and an event for the more specific state is sent.

Enabling the Service

By default the SNMP interface poller daemon is not enabled. To enable it, change the value of the enabled attribute of the service element that contains a name element with the following text: OpenNMS:Name=SnmpPoller.

<service enabled="true">
   <name>OpenNMS:Name=SnmpPoller</name>
   <class-name>org.opennms.netmgt.snmpinterfacepoller.jmx.SnmpPollerd</class-name>
   <invoke at="start" pass="0" method="init"/>
   <invoke at="start" pass="1" method="start"/>
   <invoke at="status" pass="0" method="status"/>
   <invoke at="stop" pass="0" method="stop"/>
</service>

You must restart Meridian.

Configuring the Service

The configuration file is $ONMS_HOME/etc/snmp-interface-poller-configuration.xml. The default version of this file follows:

<snmp-interface-poller-configuration xmlns="http://xmlns.opennms.org/xsd/config/snmpinterfacepoller" threads="30" service="SNMP"  up-values="1" down-values="2">
   <node-outage>
      <critical-service name="ICMP"/>
      <critical-service name="SNMP"/>
   </node-outage>
   <package name="example1">
      <filter>IPADDR != '0.0.0.0'</filter>
      <include-range begin="1.1.1.1" end="1.1.1.1"/>
      <include-range begin="::1" end="::1"/>
      <interface criteria="snmpiftype = 6" name="Ethernet" interval="300000" user-defined="false" status="on"/>
   </package>
   <!--  package name="overwritesnmpvalues">
      <filter>IPADDR != '0.0.0.0'</filter>
       <include-range begin="1.1.1.1" end="254.254.254.254" />
       <interface name="Ethernet" criteria="snmpiftype = 6" interval="300000" user-defined="false" status="on" port="161" timeout="1000" retry="1" max-vars-per-pdu="10" />
   </package-->
</snmp-interface-poller-configuration>

Explanation of the configuration options available:

snmp-interface-poller-configuration

Top-level element for the snmp-interface-poller-configuration.xml configuration file. Several global configuration attributes are available:

interval: default polling interval in milliseconds.
threads: maximum number of threads used for SNMP polling.
service: SNMP service string; almost always "SNMP".
useCriteriaFilters: Flag that indicates if interfaces that do not match the criteria attribute of an interface element in an otherwise matching package should be polled with default settings or not.

When "false" such an interface will be polled with default settings; when "true" that interface will not be polled. * up-values: comma-separated list of valid integer values (1-7) to treat as equivalent to up(1) when sending status change events for an interface. Defaults to "1". * down-values: comma-separated list of valid integer values (1-7) to treat as equivalent to down(2) when sending status change events for an interface. Defaults to "2".

node-outage: Polling will not be attempted if any of the critical service(s) contained in this element are unavailable on a node interface.
critical-service: The name attribute of this element indicates the name of a service that, when unavailable, will prevent the attempted polling of SNMP interfaces on a node interface.
package: Similar to Service Assurance and Performance Management packages, this service uses package elements to allow different settings to be used for different types of devices. Has a single attribute, name, which is mandatory.
filter: Mandatory. Behaves like filter elements in pollerd packages.
specific: Behaves like specific elements in pollerd packages.
include-range: Behaves like include-range elements in pollerd packages.
exclude-range: Behaves like exclude-range elements in pollerd packages.
include-url: Behaves like include-url in other pollerd packages.

The filter, specific, include-range, exclude-range, and include-url elements apply to the node and interface on which the SNMP interface data resides, not the SNMP interfaces themselves.

interface

Controls how, when, and (sometimes) which kinds of SNMP interfaces will be polled for status from management interfaces that match the package rules. Attributes include:

name: name for this interface element. It is generally advisable to make the name representative of the criteria filter of the interface. Required.
criteria: Criteria added to the SQL query performed on the SNMP interfaces available for polling on an interface node. Can have more than one. Lets you specify different settings for different types of interfaces. As noted above, if useCriteriaFilters is true on the top-level element, any interface that does not match the criteria filter on one of the interface elements will not be polled.
interval: polling interval for interfaces matching this element’s criteria, in milliseconds. Overrides the global setting in the top-level element for interfaces that match this element’s criteria filter.
user-defined: An unused boolean value reserved for use in the UI, should one ever exist for this service. Defaults to false.
status: When off polling will not be performed for SNMP interfaces that meet the criteria filter of this element. Defaults to on.
port: If set, overrides UDP port 161 as the port where SNMP GET/GETNEXT/GETBULK requests are sent. Valid values are between 1 and 65535.
retry: Number of retry attempts made when attempting to retrieve ifAdminStatus and ifOperStatus values from the management interface for SNMP interfaces that match this element’s criteria filter.
timeout: Timeout, in milliseconds, to wait for a response to SNMP GET/GETNEXT/GETBULK requests sent to the node interface.
max-vars-per-pdu: Number of variables to send per SNMP request. Default is "10".
up-values: Values of ifAdminStatus and ifOperStatus to treat as up values. Expects a comma-separated list of integer values between 1 and 7. Example: "1,5". Defaults to "1".
down-values: Values of ifAdminStatus and ifOperStatus to treat as down values. Expects a comma-separated list of integer values between 1 and 7. Example: "2,3,4,6,7". Defaults to "2".

Using the Service

Besides enabling the service and configuring packages and interfaces to match your use case, you must add a policy that enables polling to the foreign source definition of the import requisition(s) for the devices on which you want to use this feature.

Use the ENABLE_POLLING and DISABLE_POLLING actions of the matching SNMP interface policy to manage which SNMP interfaces this service polls along with the appropriate matchBehavior and parameters for your use case.

As an example, you could create a policy named pollVoIPDialPeers that marks interfaces with ifType 104 to be polled. Set the action to ENABLE_POLLING and matchBehavior to ALL_PARAMETERS. Add parameter ifType with 104 for the value. Once you synchronize the requisition, SNMP interface polling will begin for all SNMP interfaces with ifType 104 found on node interfaces matching the filter of a package in the SNMP interface poller config file.

As explained in the prior sections, exactly how and when the polling is performed is controlled by the settings on the interface element the SNMP interface matches in that package. If an SNMP interface does not match the criteria of any interface element in a package, default settings are used, unless useCriteriaFilters is set to true in the top-level element, in which case no polling is performed.