A stacked switch in a patch panel that responds intermittently, user tickets mentioning slowness on a single VLAN, a WAN link saturated at certain times: it is often this type of operational symptom that triggers the decision to launch an IT network audit. Before rolling out a methodology, we need to understand what the network is already telling us, through its logs, alerts, and visible bottlenecks.
Field Diagnosis Before the Network Audit: What the Symptoms Reveal
On the ground, we find that most network audits start too quickly. The technical team launches scans, collects configurations, and produces tables. The problem is that without first analyzing recent incidents and user complaints, we miss the relevant angle of attack.
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An effective audit begins with a review of support tickets from the last three to six months. We look for patterns: a remote site that accumulates disconnections, a cloud service whose performance degrades at the same time slots, a network segment where print jobs regularly fail. These weak signals guide the scope much better than a generic specifications document.
Specifically, we cross-reference these reports with SNMP or NetFlow data already available on active devices. If your network monitoring exists but no one consults its dashboards, the audit starts there: understanding why alerts are not being utilized. You will find a detailed description of the steps of an IT network audit that formalizes this sequential approach.
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Network Mapping and Inventory: Going Beyond a Simple Equipment Listing
Mapping is the backbone of any IT network audit. Competitors all talk about inventory, but the real difficulty lies elsewhere: in the gap between existing documentation and physical reality.
Shadow IT Distorts Your Mapping
We regularly discover unmanaged switches placed under a desk, personal Wi-Fi access points plugged into corporate network sockets, or VPN tunnels set up by a forgotten contractor. A network inventory that ignores shadow IT is incomplete by definition.
To ensure the reliability of the mapping, we combine several sources:
- An active scan (like Nmap or equivalent) that identifies each responding IP address, open ports, and exposed services on each segment
- An extraction of ARP tables and MAC databases from switches, which reveals connected devices even if they do not respond to ping
- A cross-reference with the CMDB or asset management spreadsheet, to identify discrepancies between what is declared and what is observed
This cross-referencing produces a list of concrete anomalies: unknown devices, duplicate IP addresses, configured but empty VLANs. Each anomaly becomes a point of investigation for the rest of the audit.
Integrating Cloud and SaaS into the Scope
Network audits that limit themselves to the LAN and internal WAN miss a growing share of traffic. Cloud environments (IaaS, PaaS) and SaaS services like Microsoft 365 generate flows that transit through your infrastructure. Auditing the network without including cloud configurations means only checking half of the traffic.
Here, we check outbound flow rules, the activation of MFA on cloud administration consoles, and connection logging. Feedback on this point varies depending on the maturity of the company, but a complete lack of visibility on cloud flows is a frequent warning signal.
Network Security Analysis and NIS2 Compliance
Security analysis goes beyond simple vulnerability scanning. In the field, we observe three critical points that automated reports do not always capture.
The first concerns firmware. A switch or firewall whose firmware has not been updated for several years accumulates known vulnerabilities. We systematically check the versions in place and compare them to the manufacturer’s security bulletins. A network device with outdated firmware is a documented open door.
The second concerns filtering rules. Firewalls accumulate rules over the years, often without cleaning. We frequently find “any-any” rules created in an emergency during troubleshooting and never deleted. The audit identifies them, classifies them by risk, and recommends their removal or replacement.
The third point concerns regulatory compliance. Since the transposition of the European NIS2 directive, network audits must include a review of security controls related to services deemed important: logging, incident management, backups, business continuity. The traceability of collected evidence becomes a requirement for competent authorities or external auditors.
Network Audit Report: Structuring Recommendations by Operational Priority
An audit report that lists two hundred points without hierarchy ends up in a drawer. The goal of the deliverable is for the IT team to be able to act on the most exposed risks as early as the following week.
We structure the recommendations into three levels:
- Immediate actions (within fifteen days): fix critical vulnerabilities, remove orphaned access, update end-of-life firmware
- Medium-term actions (one to three months): overhaul the IP addressing plan, segment VLANs according to business uses, deploy utilized network monitoring
- Structural actions (beyond three months): architecture migration, replacement of obsolete equipment, complete NIS2 compliance
Each recommendation must be linked to a risk identified during the audit. Without this explicit connection, management will not allocate the budget. We associate each point with a level of criticality, the concerned equipment or segment, and an estimated workload.
The report also includes the updated mapping, which becomes the company’s reference. This living document will serve as the basis for comparison for the next audit, allowing for the measurement of real progress in network security and performance.
A well-conducted IT network audit does not end with the delivery of the report. The last useful deliverable is a tracking table shared between the IT department and management, with deadlines and a named responsible person for each action. Without this follow-up, the same vulnerabilities will reappear in the next diagnosis.