VLANider

VLANIDer is a network analysis tool designed to identify VLAN IDs present within a network environment. It supports administrators and security professionals in mapping VLAN topology, verifying correct VLAN tagging, and performing compliance audits. The name reflects its primary function of discovering VLAN identifiers.

Overview of use: VLANIDer can operate in passive mode by monitoring traffic on trunk links to detect 802.1Q VLAN tags, and in active mode by generating lightweight probes where permitted to elicit responses from network devices. It can correlate information from protocol data units such as CDP and LLDP, as well as device configuration data, to infer VLAN assignments across switches and routers. The results are collected into a centralized inventory and can be exported for further analysis.

Features: cross-vendor compatibility, both passive and active discovery capabilities, identification of native and tagged VLANs, aggregation of findings into inventory records, export options (JSON, CSV), and basic reporting for misconfigurations or unexpected VLANs. It may include basic risk assessment to highlight potential tagging inconsistencies.

Limitations and considerations: results depend on access to network segments and on devices permitting discovery traffic. Environments with private VLANs, restricted management networks, or disabled discovery protocols may yield incomplete data. Ethical and legal considerations apply; use requires proper authorization and observance of monitoring policies.

See also: VLAN, 802.1Q, VLAN tagging, CDP, LLDP, network discovery.