How to handle devices missed during network discovery. Tired of chasing down ghost devices that should be managed but won't authenticate during your scans? Mastering the protocol, reachability, and credential management is the key to maintaining an accurate network discovery inventory. Before we begin, be sure to subscribe to NinjaOne's IT Video Hub and our YouTube channel for more tech content like this. Establishing reachability and connectivity. To ensure your probe can communicate with target assets, follow these connectivity verification steps. Verify basic connectivity by pinging the management IP to rule out basic connectivity or routing issues. Test the required TCP and UDP ports, including 22 for SSH, 135 and 445 for WMI, 5985 and 5986 for WinRM, and UDP 161 for SNMP to confirm that required management services are reachable. Identify routing obstacles such as VRF, NAT, or asymmetric routing issues that may be masking or blocking access to your devices. Validating credentials and protocol access. Prevent authentication failures by ensuring your access rights and protocols are correctly configured. Confirm credential validity for SNMP V2c/V3 credentials and Windows WMI or WinRM credentials, as well as SSH credentials where applicable, to avoid authentication failures. Assign sufficient privileges to discovery accounts so they can retrieve the required hardware and software data. Store validated credentials in secure, reusable profiles with rotation policies where appropriate to maintain consistent long-term access. Resolving policy, topology, and identification blocks. Clear the path for discovery traffic by reviewing your security configurations and device templates. Allow list management subnets within your ACLs and firewalls so discovery traffic can pass between the probe and target devices. Verify routing, VRF paths, segmentation, and VLAN assignments to ensure management networks remain reachable. Map sys object IDs to vendor templates and import necessary MIBs to ensure SNMP devices are classified accurately. Normalize CLI prompts where applicable for consistent parsing across legacy or unsupported equipment. Scaling visibility with agents, passive scans, and governance. Maintain more complete and reliable inventory visibility by using multiple discovery methods and strict reconciliation. Deploy agents or passive listeners to fill visibility gaps for devices that are isolated or block direct polling. Schedule regular re-scans to capture environmental changes and confirm that previous discovery fixes are still effective. Reconcile discovered assets against your inventory, merging duplicates and tracking unresolved assets as exceptions with assigned owners and due dates. Comprehensive asset visibility is an important part of a proactive security posture. When you eliminate discovery blind spots, you empower your team to manage, monitor, and protect every endpoint across your entire IT estate with confidence. For more information, check out our official blog post on how to handle devices missed during network discovery, linked in the description below.