Open-AudIT uses Nmap for its initial scan of networks and devices. The options that Open-AudIT passes to Nmap are detailed on the page Discovery Scan Options. The options available for running a discovery will depend on your license.
Open-AudIT Community will use the default options as per the configuration for all discoveries.
Open-AudIT Professional has the ability to choose from a pre-defined list of discovery scan options, per discovery.
Open-AudIT Enterprise has the ability to choose from a pre-defined list of discovery scan options and also to customise individual options per discovery.
The default discovery scan option is the UltraFast set.
Some networks can have issues with this set because of their configuration. Some users see SNMP port 161 scans returning open|filtered. For an UltraFast scan this is not sufficient to trigger a device scan. Nmap will need to see an "open" response to trigger a device scan. Devices also must respond to an Nmap ping. If these defaults do not suit, depending on your version you can change the configuration defaults, choose another discovery scan option set or change the individual options passed to Nmap.
If you are a Community or Professional user and none of these options suit because of your network configuration, you can either correct your network configuration or upgrade to Enterprise to cater to your network, without making changes.
We often see routers or firewalls sending traffic back to Nmap on behalf of IP addresses (even when there are no devices at those addresses). In all cases we would suggest correcting this activity as a first step. The Open-AudIT server should have full access to the target networks. If this is not acceptable, you have the option to license Open-AudIT Collector (one free license is included with Enterprise). That way you can deploy a Collector into a remote network and only open a single port between the Collector and Server. Obviously the Collector will then need full network access to the target devices.
There are multiple ways to discovery your networks - if you're not sure which is right for you, or you need assistance, just contact Opmantek. We're here to help