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Back-end processes in NAV

This page has not been updated for several years, and may be quite outdated for NAV 4

NAV has a number of back-end processes. This page attempts to give an overview of them.

The NAV processes

:!: The shell command nav list lists all back-end processes. nav status tells you if they are running as they should. With reference to the nav list, jump directly to the relevant section in this document:

nav list gives you this list:

Building the network model


Key information

Process name ipdevpoll
Polls network Yes
Brief description Collects SNMP data from equipment in the netbox table and stores data regarding the equipment in a number of tables. Does not build topology.
Depends upon Seed data must be filled in the netbox table, using the Seed Database tool
Updates tables netbox, netboxsnmpoid, netboxinfo, device, module, gwportprefix, prefix, vlan, interface, swportallowedvlan
Run mode Daemon process
Default scheduling Polling is organized into jobs in ipdevpoll.conf, so is job scheduling.
Config file ipdevpoll.conf
Log files ipdevpoll.log
Programming language Python
Further doc


  • jobs and plugins
    All ipdevpoll's work is done by plugins. Plugins are organized into jobs, and jobs are scheduled for each active IP device individually.
  • inventory job
    Polls for inventory information every 6 hours (by default). Inventory information includes interfaces, serial numbers, modules, VLANs and prefixes.
  • profiler job
    Runs every 5 minutes, profiling devices if deemed necessary. NAV has an internal list of SNMP OIDs that are tested for compatibility with each device. This is used to create a sort of profile that says what the device supports - the profile is typically used to produce a Cricket configuration that will collect statistics from proprietary OIDs.
  • logging job
    Runs every 30 minutes and collects log-like information from devices. At the time being, only the arp plugin runs, collecting ARP caches from routers. ARP data is logged to a table, and aids in topology detection and client machine tracking.


Key information

Process name mactrace
Alias Mac-to-switch port collector / getBoksMacs / cam logger
Polls network Yes
Brief description Collects mac addresses behind switch table data for all switches (cat GSW, SW, EDGE). The process also checks for spanning tree blocked ports.
Depends upon ipdevpoll must have created the swport tables for the switches.
Updates tables cam (mac adresses), netboxinfo (CDP neighbors), swp_netbox (the candidate list for the physical topology builder), swportblocked (switch ports that are blocked by spannning for a given vlan).
Run mode cron
Default scheduling every 15 minutes ( 11,26,41,56 * * * * ). 24 threads as default
Config file getBoksMacs.conf
Log file getBoksMacs.log
Programming language Java
Further doc NAVMore report ch 2.1 (Norwegian), tigaNAV report ch 5.4.5 and ch 5.5.3


  • cam data is not collected from ports that are connecting to other switches (as determined by the physical topology builder). Typically the cam records are stored initually before the topology is built. When topology information is in place the end time in the relevant cam records are set.
  • The command line tool offers a means of deleting old cam (and arp) entries.

The algorithm

FIXME The following is cut and paste from the referenced chapters in NAVMore and tigaNAV. Rewrite/translate to one text.

CAM-loggeren kjører hvert kvarter. Det som skjer da er at alle svitsjer (SW og KANT) blir hentet fra databasen og lagt i en kø. Så startes et antall tråder (24 er default) som alle jobber mot denne køen. Hver tråd sjekker om det ligger en boks i køen, og hvis så er tilfellet hentes denne ut og tråden foretar spørring med SNMP. Når dette er ferdig sjekker den køen igjen. Dersom køen er tom avslutter tråden. Alle trådene vil altså hente bokser fra køen helt til denne er tom, og da har alle resterende bokser en tråd som jobber mot dem. Dette sikrer at alle trådene hele tiden har arbeid å gjøre selv om noen bokser tar mye lenger tid å hente data fra enn andre.

The cam logger, responsible for the collection of MAC addresses and CDP data, has been updated to make use of the OID database. This has greatly simplified its internal structure as all devices are now treated in a uniform manner; the immediate benefit is that data collection is no longer dependent on type information and no updates should be necessary to support new types. Upgrades in the field can happen without the need for additional updates to the NAV software.

The cam logger collects the bridge tables of all switches, saving the MAC entries in the cam table of the NAVdb. Additionally, it collects CDP data from all switches and routers supporting this feature; the result is saved in the swp_netbox table for use by the network topology discover system.

While its basic operation remains the same, it has been rewritten to take advantage of the OID database; the internal data collection framework has been unified and all devices are treated in the same manner. Thus, data collections are no longer based on type information and a standard set of OIDs are used for all devices. When a new type is added to NAV the cam logging should “just work”, which is a major design goal of NAV v3.

One notable improvement is the addition of the interface field in the swport table. It is used for matching the CDP remote interface, and makes this matching much more reliable. Also, both the cam and the swp_netbox tables now use netboxid and ifindex to uniquely identify a swport port instead of the old netboxid, module, port-triple. This has significantly simplified swport port matching, and especially since the old module field of swport was a shortened version of what is today the interface field, reliability has increased as well.


Key information

Process name navtopology
Alias Physical and VLAN Topology Builder
Polls network No
Brief description Builds NAV's model of the physical network topology as well as the VLAN sub-topologies
Depends upon mactrace fills data in swp_netbox, representing the list of physical neighbor candidates. This is the data that the physical topology builder uses.
Updates tables Sets the to_netboxid and to_swportid fields in the swport and gwport tables.
Run mode cron
Default scheduling every hour (35 * * * *)
Config file None
Log file navtopology.log
Programming language Python


Physical topology

The topology discovery system builds NAV's view of the network topology based on cues from information collected previously via SNMP.

The information cues come from routers' IPv4 ARP caches and IPv6 Neighbor Discovery caches, interface physical (MAC) addresses, switch forwarding tables and CDP (Cisco Discovery Protocol). The mactrace process has already pre-parsed these cues and created a list of neighbor candidates for each port in the network.

The physical topology detection algorithm is responsible for reducing the list of neighbor candidates of each port to just one single device.

In practice the use of CDP makes this process very reliable for the devices supporting it, and this makes it easier to correctly determine the remaining topology even in the case of missing information. CDP is, however, not trusted more than switch forwarding tables, as CDP packets may pass unaltered through switches that don't support CDP, causing CDP data to be inaccurate.

VLAN topology

After the physical topology model of the network has been built, the logical topology of the VLANs still remains. Since modern switches support 802.1Q trunking, which can transport several independent VLANs over a single physical link, the logical topology can be non-trivial and indeed, in practice it usually is.

The vlan discovery system uses a simple top-down depth-first graph traversal algorithm to discover which VLANs are actually running on the different trunks and in which direction. Direction is here defined relative to the router port, which is the top of the tree, currently owning the lowest gateway IP or the virtual IP in the case of HSRP. Re-use of VLAN numbers in physicallyq disjoint parts of the network is supported.

The VLAN topology detector does not currently support mapping unrouted VLANs.

Monitoring the network


Key information

Process name pping
Alias The status monitor / parallel pinger
Polls network Yes
Brief description Pings all boxes in the netbox table. Works effectively in parallel, being able to ping a large number of boxes. Has configurable robustnes criteria for defining when a box actually is down.
Depends upon Netboxes to be in the netbox table.
Updates tables Posts events on the eventq table. Sets the netbox.up value in addition.
Run mode daemon
Default scheduling Pings all hosts every 20 second. Waits maximum 5 second for an answer. After 4 “no-answers” the box is declared down as seen from pping.
Config file pping.conf
Log file pping.log
Programming language Python
Further doc See below, based on and translated from NAVMore report ch 3.4 (Norwegian)


pping is a daemon with its own (configurable) scheduling. pping works in parallel which makes each ping sweep very efficient. The frequency of each ping sweep is per default 20 seconds. The maximum allowed response time for a host is 5 seconds (per default). A host is declared down on the event queue after four consecutive “no responses” (also configurable). This means that it takes between 80 and 99 seconds from a host is down till pping declares it as down.

Please note the event engine will have a grace period of one minute (configurable) before a “box down warning” is posted on the alert queue, and another three minutes before the box is declared down (also configurable). In summery expect 5-6 minutes before a host is declared down.

The configuration file pping.conf lets you adjust the following:

parameter description default
user the user that runs the service navcron
packet size size of the icmp packet 64 byte
check interval how often you want to run a ping sweep 20 seconds
timeout seconds to wait for reply after last ping request is sent 5 seconds
nrping number of requests without answer before marking the device as unavailable 4
delay ms between each ping request 2 ms

In addition you can configure debug level, location of log file and location of pid file.

Note: In order to uniquely identify the icmp echo response packets pping needs to tailor make the packets with its own signature. This delays the overall throughput a bit, but pping can still manage 90-100 hosts per second, which should be sufficient for most needs.

Algorithm - one ping sweep

pping has three threads:
  1. Thread 1 generates and sends out the icmp packets.
  2. Thread 2 receives echo replies, checks the signature and stores the result to RRD.
  3. The main thread does the main scheduling and reports to the event queue.

Thread 1 works this way:
  FOR every host DO:
    1. Generate an icmp echo packet with: (destination IP, timestamp, signature)
    2. Send the icmp echo.
    3. Add host to the "Waiting for response" queue.
    4. Sleep in the configured ''delay'' ms (default 2 ms). This delay will spread out the response times, which in 
       turn reduces the receive thread queue and will in effect make the measured response time more accurate.

Thread 2 works this way:
  As long as thread 1 is operating and as long as we have hosts in the "Waiting for response" queue, with a
  timout of 5 seconds (configurable):
    1. Check if we have received packets
    2. Get the data (the icmp reply packet)
    3. Verify that the packet is to our pid. 
    4. Split the packet in (destination IP, timestamp, signature)
       If IP is wrong or signature is wrong, discard.
    5. If we recognize the IP address on the "Waiting for response" queue, update response time for the host and
       remove the host from the "Waiting for response" queue.

When thread 2 finishes the sweep is over. If hosts are remaining on the "Waiting for response" queue, we set
response time to "None" and increments the "number of consecute no-reply" counter for the host.

When thread 3 detects that a host has to many no-replies a down event is posted on the event queue.

Note that the response times are recorded to RRD which gives us response time and packet loss data as an extra bonus.


Key information

Process name servicemon
Alias The service monitor
Polls network Yes
Brief description Monitors services on netboxes. Uses implemented handlers to deal with a growing number of services; currently supporting ssh, http, imap, pop3, smtp, samba, rpc, dns and dc.
Depends upon The service and serviceproperty tables must have data. This is filled in by Edit Database when the NAV administrator registers services that he wants to monitor.
Updates tables Posts servicemon events on the eventq table.
Run mode daemon
Default scheduling Checks each service every 60 second. Has varying timouts for different services, between 5 and 10 seconds. If a service does not respond three times in a row, servicemon declares it down.
Config file servicemon.conf
Log file servicemon.log
Programming language Python
Further doc See the servicemon page and/or NAVMore report ch 3.5 (Norwegian)


  • see the NAVMore report as referenced for details


Key information

Process name thresholdMon
Alias The threshold monitor
Polls network No
Brief description At run-time, it fetches all the thresholds in the RRD database and compares them to the datasource in the corresponding RRD file. If the threshold has been exceeded, it sends an event containing relevant information. The default threshold value is 90% of maximum.
Depends upon The RRD database has to be filled with data. This is done by makeCricketconfig. In addition you must manually run a command line tool,, for setting the threshold to a configured level. A more advanced solution for setting different threshold is under development.
Updates tables eventq with thresholdmon events
Run mode cron
Default scheduling every 5 minutes ( */5 * * * * )
Config file fillthresholds.conf
Log file thresholdMon.log
Programming language Python
Further doc See ThresholdMonitor


The event and alert system


Key information

Process name eventEngine
Alias The event engine
Polls network No
Brief description The event engine processes events on the event queue and posts alerts on the alert queue. Event engine has a mechanism to correlate events; i.e. if the ppinger posts up events right after down events, this will not be sent as boxDown alerts, only boxDown warnings. Further if a number of boxDown events are seen, event engine looks at topology and reports boxShadow events for boxes in shadow of the box being the root cause.
Depends upon The various monitors need to post events no event queue (with target event engine) in order for event engine to have work. alertmsg.conf needs to be filled in for all events, messages on alertqmsg (and alerthistmsg) are formatted accordingly.
Updates tables Deletes records from eventq as they are processed. Posts records on alertq with adhering alertqvar and alertqmsg, similarly alerthist with adhering alerthistvar and alerthistmsg.
Run mode daemon
Default scheduling Event engine checks the eventq every ??? seconds. boxDown-warning-wait-time and boxDown-wait-time are configurable values. Parameters for module events are also configurable. Servicemon eventes are currently not; a solution is looked upon.
Config file eventEngine.conf
Log file eventEngine.log
Programming language Java
Further doc NAVMore report ch 3.6 (Norwegian). Updates in tigaNAV report ch 4.3.1.


  • eventEngine is plugin based with two classes of plugins; one for eventtypes and one for physical devices. Further details in the referenced documentation.


Key information

Process name maintengine
Alias The maintenance engine
Polls network No
Brief description Checks the defined maintenance schedules. If start or end of a maintenance period occurs at this run time, the relevant maintenanceEvents are posted on the eventq, one for each netbox and/or service in question.
Depends upon NAV users must set up maintenance schedule which in turn is stored in the maintenance tables (maint_task, maint_component).
Updates tables Posts maintenance events on the eventq. Also updates the maint_task.state.
Run mode cron
Default scheduling Every 5 minutes ( */5 * * * * )
Config file None
Log file maintengine.log
Programming language Python
Further doc Old doc: tigaNAV report ch 8. The maintenance system was rewritten for NAV 3.1. See here for more.


  • See referenced doc.


Key information

Process name alertEngine
Alias The alert engine
Polls network No
Brief description Alert engine processes alerts on the alert queue and checks whether any users have subscribed to the alert in their active user profile. If so, alert engine sends the alert to the user, either as email or sms, depending on the profile. Alert Engine sends email itself, whereas sms messages are inserted on the sms queue for the sms daemon to manage. If a user has selected queueing email messages, alert engine uses the alertprofiles.queue table.
Depends upon eventEngine must be running and do the alertq posting. NAV users must have set up their profiles, if their are no matches here, alertq will simply delete the alerts.
Updates tables Deletes records from alertq with adhering alertqvar and alertqmsg. Inserts records on alertprofiles.smsq. User profiles that requires queued email messages, the alertprofile.queue table is used.
Run mode daemon
Default scheduling Checks for new alerts every 60 seconds per default.
Config file alertengine.cfg
Log file alertengine.log og alertengine.err.log
Programming language Python
Further doc NAVMore report ch 3.7 and 3.8 (Norwegian).


  • See the referenced doc.


Key information

Process name smsd
Alias The SMS daemon
Polls network No
Brief description Checks the navprofiles.smsq table for new messages, formats the messages into one SMS and dispatches it via one or more dispatchers with a general interface. Support for multiple dispatchers are handled by a dispatcher handler layer.
Depends upon alertEngine fills the navprofiles.smsq table
Updates tables Updates the sent and timesent values of navprofiles.smsq
Run mode Daemon process
Default scheduling Polls the sms queue every x minutes
Config file smsd.conf
Log file smsd.log
Programming language Python (Perl in 3.1)
Further doc subsystem/smsd/README in the NAV sources describes the available dispatchers and more



As described when given the -–help argument:

Usage: smsd [-h] [-c] [-d sec] [-t phone no.]

  -h, --help            Show this help text
  -c, --cancel          Cancel (mark as ignored) all unsent messages
  -d, --delay           Set delay (in seconds) between queue checks
  -t, --test            Send a test message to <phone no.>

Especially note the --test option, which is useful for debugging when experiencing problems with smsd.


The configuration file smsd.conf lets you configure the following:

parameter description default
username System user the process should try to run as navcron
delay Delay in seconds between queue runs 30
autocancel Automatically cancel all messages older than 'autocancel', 0 to disable. Format like the PostgreSQL interval type, e.g. '1 day 12 hours'. 0
loglevel Filter level for log messages. Valid options are DEBUG, INFO, WARNING, ERROR, CRITICAL INFO
mailwarnlevel Filter level for log messages sent by mail. ERROR
mailserver Mail server to send log messages via. localhost
dispatcherretry Time, in seconds, before a dispatcher is retried after a failure 300
dispatcherN Dispatchers in prioritized order. Cheapest first, safest last. N should be 1,2,3,… dispatcher1 defaults to GammuDispatcher

In addition, some dispatchers need extra configuration as described in comments in the config file.


Key information

Process name snmptrapd
Alias The SNMP trap daemon
Polls network No
Brief description Listens to port 162 for incoming traps. When the snmptrapd receives a trap it puts all the information in a trap-object and sends the object to every traphandler stated in the “traphandlers” option in snmptrapd.conf. It is then up to the traphandler to decide if it wants to process the trap or just discard it.
Depends upon
Updates tables Depends on “traphandlers”. Posts on eventq would be typical
Run mode Daemon process
Default scheduling
Config file snmptrapd.conf
Log file snmptrapd.log and snmptraps.log
Programming language Python
Further doc -

Collecting statistics


Key information

Process name makecricketconfig
Alias The Cricket configuration builder
Polls network No
Brief description
Depends upon That ipdevpoll has filled the gwport, swport tables (and more…)
Updates tables The RRD database (rrd_file and rrd_datasource)
Run mode cron
Default scheduling Every night( 12 5 * * * )
Config file None
Log file cricket-changelog
Programming language python
Further doc How to configure Cricket addons in NAV v3


The Cricket collector (not NAV)

Key information

Process name collect-subtrees
Alias cricket collector (not NAV)
Polls network Yes
Brief description Polls routers and switches for counters as configured in the cricket configuration tree.
Depends upon makecricketconfig to build the configuration tree
Updates tables Updates RRD files
Run mode cron
Default scheduling Every 5 minute (Pre-NAV 3.2 had a one minute run mode for gigatit ports. As of NAV 3.2 64 bits counters are used and the 5 minutes run mode is used for all counters).
Config files directory tree under cricket-config/
Log file cricket/giga.log og cricket/normal.log
Programming language not relevant
Further doc not relevant


Key information

Process name cleanrrds
Alias RRD cleanup script
Polls network No
Brief description This script finds all the rrd-files that we are using. The purpose of the script is to delete all the rrd-files that are no longer active, to save disk-space.
Depends upon -
Updates tables -
Run mode cron
Default scheduling nightly ( 0 5 * * * )
Config file ?
Log file ?
Programming language Perl
Further doc -


  • if a rrd-file is found and is in the RRD database, leave it alone.
  • if a rrd-file is found that is not in the database, check the last update-time. If the time for last update is less than 2 weeks ago, leave it alone. Otherwise delete the file.

Other systems


Key information

Process name logengine
Alias The Cisco syslog analyzer
Polls network No
Brief description Analyzes cisco syslog messages from switches and routers and inserts them in a structured manner in the logger database. Makes searchein for log messages of a certain severity easy, etc.
Depends upon syslogd to run on the NAV machine. Parses the syslog for cisco syslog messages.
Updates tables The tables in the logger database
Run mode cron
Default scheduling every minute ( * * * * * )
Config file logger.conf
Log file None
Programming language Python
Further doc NAVMore report ch 2.4 (Norwegian).


  • see referenced doc. Note that this system at one time was intended for NAVs own logs. This idea was aborted at a later stage.


Key information

Process name
Polls network
Brief description
Depends upon
Updates tables
Run mode
Config file arnold/arnold.cfg, arnold/noblock.cfg og arnold/mailtemplates/*
Log file arnold/arnold.log
Default scheduling
Programming language
Further doc Arnold
backendprocesses.txt · Last modified: 2015/09/24 12:48 by morten