Network discovery

Introduction

NetXMS is capable of discovering your network automatically. Network discovery module can operate in two modes - passive and active.

In passive mode, information about new hosts and devices obtained from ARP tables and routing tables of already known devices. NetXMS starts with it’s own ARP cache and routing table.

In active discovery mode, NetXMS server will send an ICMP echo requests to all IP addresses in given range, and consider each responding address for adding to database. If zoning is used, server sends echo request only in zone 0, in other zones requests are sent by proxies. For each new device found NetXMS server tries to gather additional information using SNMP and NetXMS agent, and then adds it to database. By default NetXMS server will add all discovered devices to database, but you can limit it by using discovery filters. Default SNMP credentials can be set in Default SNMP credentials.

Default intervals are 2 hours for active discovery and 15 minutes for passive discovery. These values can be changed in Network Discovery configuration. Number of discovery poller threads changes dynamically and is defined by server configuration parameters ThreadPool.Discovery.BaseSize and ThreadPool.Discovery.MaxSize. More information about server configuration parameters can be found here.

Configuring Network Discovery

To change network discovery settings, go to main menu of management client and choose Configuration ‣ Network Discovery. Configuration form will open:

General

In this section, you can choose network discovery mode, chose if source node of SNMP Trap or syslog source address should be used for discovery.

Schedule

For passive discovery interval (in seconds) is selected. For active discovery you cen choose either an interval (in seconds) or cron format schedule (see here for more details).

Filter

In this section, you can define filter for adding new nodes to NetXMS database. Filtering options are following:

No filtering

Any new device found will be added to database. This is the default setting.

Custom script

You can choose NXSL script from the Script Library to work as discovery filter. Custom filtering script will get object of class NewNode as first parameter (special variable $1), and should return true to allow node inclusion into database.

Automatically generated script

This option can be used if you need only simple filtering. When selected, additional options controls what nodes will be added to database:

Accept node if it has NetXMS agent	If checked, only nodes with NetXMS agent detected will pass the filter.
Accept node if it has SNMP agent	If checked, only nodes with SNMP agent detected will pass the filter.
Accept node if it is within given range or subnet	Only accept nodes within given address range or subnet. Address ranges can be configured in Address Filters section.

Please note that first two options (NetXMS agent presence and SNMP agent presence) forms OR condition - if both are checked, any node with either SNMP agent or NetXMS agent will pass. Address range check and first two options forms AND condition - so if potential node does pass agent presence check, but is not in allowed IP address range, it will not be accepted. In other words, if all three options are checked, condition for new node to pass filter can be written as following:

if (node has NetXMS agent or node has SNMP agent) and node within given range then pass

Active Discovery Targets

In this section, you can define address ranges for active discovery. NetXMS server will periodically send ICMP echo requests to these addresses, and consider for addition to database every responding device. This list has no effect if active discovery is off.

Address Filters

In this section you can define address ranges for automatically generated discovery filter. This list has no effect if discovery is off or filter is not set to Automatically generated script.