Safe Network Scanning Practices: Top 5 Tips For Your First Network Scan

Safe network scanning practice starts with knowing what you are scanning and how your scanner will behave before you run it.

Your first network scan can quickly become harder to manage than expected. A range that is too large can return too many results. Aggressive settings can create extra network traffic. A small setup mistake can even trigger security alerts or scan the wrong systems.

In this article, we will cover five practical tips to help you run your first network scan more safely and get more reliable results.

Tip 1: Start With a Small Network Range

For your first scan, avoid scanning the entire network at once. Start with a small, known IP range so you can see how the scanner behaves and review the results more easily.

For example, you can begin with a /24 subnet, which contains 256 IP addresses, instead of a /16, which contains 65,536.

A smaller range also reduces unnecessary network traffic and makes it easier to spot unexpected devices or configuration issues. If something looks wrong, you only need to inspect a limited range instead of sorting through hundreds of results.

Once the first scan looks correct, gradually expand the scope to other subnets or approved network ranges.

Tip 2: Use a Dry Run When Available

Not every scanner supports this, but if yours does, use a dry run before sending any scan traffic. It gives you a chance to catch mistakes before the actual scan begins.

A dry run can help you confirm:

• The target IP range
• The estimated number of hosts
• The protocols and ports being used
• Timeout and concurrency settings
• Whether the range includes routed or public addresses

The dry run acts as a final safety check. If the scope, workload, or settings look different from what you expected, fix them first and only start the scan when everything looks right.

For instance, if you planned to scan one office subnet but the dry run shows thousands of hosts, do not start the scan. You should recheck the subnet mask, compare the target with your approved IP ranges, and correct the scope if needed. Once the host count and scan range match what you expected, you can start the actual scan. 

Tip 3: Keep Ports and Concurrency Under Control

More ports and higher concurrency can make a scan more aggressive than you actually need. A simple rule is to avoid scanning every possible port unless you have a clear reason to do so.

For a first scan, you may start with a small set of ports and a moderate number of simultaneous requests. You should focus on ports that are relevant to the devices you expect to find. For example, you might scan common services such as:

• 22 for SSH
• 80 and 443 for web interfaces
• 445 for SMB
• 3389 for Remote Desktop
• 9100 for network printers

The same applies to concurrency. Higher concurrency can speed up a scan, but it also sends more requests at the same time. On a busy network, this can create traffic spikes or trigger security monitoring.

A practical approach is to start with the scanner's default concurrency setting. If the scan is stable but too slow, increase concurrency gradually rather than jumping straight to a high value.

For example, users may report that printers are responding slowly during the scan. Your monitoring tools may also show a sudden spike in network traffic. If that happens, pause the scan and lower the concurrency before continuing.

The goal is not to finish the scan as fast as possible. It is to collect useful results without putting unnecessary load on the network.

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Tip 4: Scan Regularly, Not Aggressively

You don’t need to run an aggressive scan every time you want to check what is connected to your network. In many cases, a lighter scan performed more regularly gives you more useful information over time.

You may run a lightweight scan every week to detect new or missing devices. If something unusual appears, such as new unknown devices appearing on the network, you can then run a deeper scan on that specific range.

This approach helps you avoid putting unnecessary load on the network. It also makes changes easier to spot because you are comparing smaller, more frequent snapshots. 

A practical routine could be:

• Run a lightweight scan on a regular schedule
• Compare the latest results with your previous scan
• Check for new, missing, or changed devices
• Use deeper scanning only when you need more details

Explore the Advanced Network Discovery Method here

Tip 5: Review & Secure Scan Results

A network scan is not finished when the scanner stops running. You still need to review the results before using them for inventory, troubleshooting, or follow-up scans.

Start by checking whether the results make sense. Look for:

• Unknown IP addresses
• Duplicate devices
• Missing hostnames or MAC addresses
• Devices that appear in an unexpected subnet
• Open ports that you did not expect to see

If your scan finds a device with an unfamiliar hostname, do not immediately treat it as a new asset. Check the MAC address, manufacturer, assigned IP, and previous scan results first. It may be a guest device, a temporary device, or an existing asset using a new IP address.

You should also secure the scan results after reviewing them. Scan results can contain sensitive network information such as IP addresses, MAC addresses, hostnames, device types, and open ports.

These files should be stored in an approved internal location, and access should be limited to people who need them. Avoid leaving scan exports in shared folders, personal downloads, or temporary locations longer than necessary.

FAQs

1. Why do some devices not appear in a network scan?

A device may be connected to the network but still not appear in the scan. It could be offline, blocking discovery traffic, located behind another network segment, or configured not to respond to certain protocols.

If a device is missing, first confirm that it is powered on and connected. Then check whether the scanner can reach its subnet and whether firewall rules are blocking the discovery method being used.

2. Can network scanning damage devices?

Most modern devices can handle normal network discovery without problems. However, older hardware, embedded systems, IoT devices, and specialized equipment may react poorly to aggressive or unusual requests. This is why it is important to understand what types of devices are on the network before using deeper scanning methods.

3. Can a network scan be detected by security tools?

Yes. Firewalls, IDS/IPS platforms, SIEM systems, and endpoint security tools may detect network scanning activity. A legitimate scan can sometimes look similar to reconnaissance. For planned scans, it is a good idea to make sure your security team knows where the scan is coming from and why it is being performed.

Before scanning, make sure you have authorization and let your security or network team know the source IP, target range, and planned timing.

4. What is the difference between network discovery and vulnerability scanning?

Network discovery focuses on identifying which devices are connected and collecting basic information such as IP addresses, hostnames, MAC addresses, and open services.

Vulnerability scanning goes further. It checks systems for known security weaknesses, outdated software, or configuration issues. Because it performs deeper checks, vulnerability scanning usually requires more planning and stricter authorization.

5. Should I use an agentless scanner or install agents on devices?

It depends on what information you need. Agentless scanning is useful for quickly discovering devices across a network without installing software on every endpoint. Agent-based tools usually provide deeper and more consistent information about managed devices.

For an initial network inventory, agentless discovery is often a practical starting point. You can then use agents or management integrations when you need more detailed endpoint data.

Final Thoughts

Safe network scanning does not mean making every scan as deep or as fast as possible. It means using the right scope, settings, and level of intensity for what you actually need to discover.

For your first scan, keep the process simple. Start with a smaller range, validate the scan before running it, control ports and concurrency, and review the results carefully afterward.

Put these safe network scanning practices into action with the AssetLoom Free Network Scanner. Discover devices across your network, review scan results, and export the data you need without installing agents on every device.