How to scan for IP addresses in a local network

When you experience network problems, there are steps that you can take in order to investigate and solve the problem. Therefore, you are probably going to need to know the addresses of your equipment so that you can identify the device that is the cause of the problem.

How to find IP addresses on a network:

In order to get a list of the IP addresses of all of the devices connected to your network. Follow these steps:

  1. Open a terminal window to get to the command line.
  2. Issue the command ipconfig and press Return. On Linux type ifconfig instead.
  3. Enter the command arp -a to get more information.

This will give you a bare list of IP addresses, but then you will need to utilize other tools in order to investigate further or troubleshoot network problems.

We get into a lot of detail below. If you only have time for a quick glance, here is our list of the best IP address scanner and tracker tools:

  • Terminal or Command line Basic IP scanning can be performed from the command line.
  • Angry IP Scanner Free IP address scanner that installs on Windows, Linux, and Mac OS. It doesn’t perform DHCP reconciliation.
  • SolarWinds Ping Sweep with Engineer’s Toolset (FREE TRIAL) Powerfull tool that comes bundled in with the Engineer’s Toolset for Windows with a GUI.
  • SolarWinds Port Scanner (FREE TOOL) is an IP address scanner that allows users to scan IP addresses in their network. Scans can be run through the graphical user interface (GUI) or the command line.
  • SolarWinds IP Tracker (FREE DOWNLOAD) A lightweight free tool that will scan a network with up to 256 IP addresses. It won’t coordinate with your DHCP server, but it will spot duplicate addresses.
  • MyLanViewer – A free IP address scanner for Windows. It will detect rogue devices and fake DHCP servers.
  • SolarWinds IP Address Scanner (FREE TRIAL) Part of the company’s IPAM solution. It installs on Windows Server and is a paid product, but you can get it on a 30-day free trial. The IPAM will coordinate with your DNS and DHCP servers to give you a complete DDI solution.
  • ManageEngine OpUtils (FREE TRIAL) Package that combines an IP address manager and a switch port manager plus a bundle of extra network management tools. A free version of the utility gives you a network scanner.

In this guide, you will learn about a quick way to find out the IP addresses on your network, and then you will read about some basic tools that will get that information in a more digestible format and give you options to manage addresses.

If you are just looking to find your own IP address then try this guide instead > How to Find Your IP Address in under 30 seconds.

Analyze investigation results

The ipconfig command will return a set of results for each of the network adapters that you have set up on your computer. Those adapters that are not active will show the result, Media disconnected, so you can ignore those.

You need to look for adapter results that show IPv4 Address and Default Gateway entries.

ipconfig results

You now have the addresses of two devices on your network. The IPv4 address is the network address of the computer that you are using, and the default gateway result is the IP address of your router.

The ARP results will give you a list of all of the allocated addresses on your network.

arp results

If you see several batches of results, look for the one that has the IP address that was reported as your computer’s IP address in the ipconfig results. The list of IP addresses that you see below that shows all of the other addresses that have been allocated on your network. So the complete list is all of these addresses including the address of your computer.

In the ARP results shown above, you can see four addresses that are labeled dynamic and six addresses that are categorized as static. If you have not made any intervention at all to allocate addresses manually to devices on your network, then all of the physical pieces of equipment will have dynamic addresses. The static addresses are used for administration by your router. The first address in the list is the address of your router. This should match the Default Gateway address that you saw in the ipconfig results.

In the illustrations in this section, you can see that the ipconfig and arp commands have revealed the address of the router, the address of the computer from which the commands were issued, and the network addresses of four more devices that are connected to the network.

Address allocation

Keeping track of the address allocations on your network is very important. You can choose two ways to allocate IP addresses. In one method, which is the static IP address, you enter an address into the network settings of each device. As you perform this task, you need to keep a central record of those address allocations and be careful not to repeat addresses.

The second method that you can use to allocate addresses is the dynamic IP address system. This scenario is now widely used by network administrators. In this scenario, each device, when connecting to the network has to contact a central server and request an address. This server operates the DHCP system. DHCP stands for the Dynamic Host Configuration Protocol. In networking terminology, a computer that is connected to a network is called a « host. »

Under DHCP no device is allocated an address permanently. Instead, the addresses are applied to each device on a « lease. » This lease will expire and then the computer will either be given a new lease on the same address or a lease on a new address.

Dynamic or static addresses

The dynamic addressing method requires a lot more equipment than the static address allocation method. However, it is easier to automate than the static address method. If you have a small network, you could easily operate a static method. However, the automation that is available with the DHCP system makes it more attractive to the administrators of large networks.

Networks use hostnames as well as IP addresses to identify devices. Under the dynamic address system, the hostname stays the same, but the IP address associated with it will change frequently. Because of address changes, it is necessary to automate the mapping between the host names and IP address that are held in your networks Domain Name Server. So, dynamic addressing requires automation tools. On the other hand, having to manually assign an address for each computer, mobile device and printer connected to the network can become very time consuming for administrators of large networks.

As a small network grows, the recording of IP address allocations needs to be very strictly controlled. Any slip-ups in the listing of assigned addresses can result in networking disasters. So, you are going to need tools to help monitor IP address allocation even in small networks.

DDI

A full-blown dynamic addressing system needs three elements, which are summarized by the acronym « DDI. » The two Ds in that acronym represent DNS and DHCP; the « I » stands for IP Address Management, which is often abbreviated to IPAM. This trio is necessary because the DNS server has to be updated whenever the DHCP server assigns a new address. The IP Address Manager is needed in order to check on the addresses that are currently live on the network and match the current status up to the records in the DHCP server.

Improved IP scan results

An IP address scanner is just going to give you more or less the same information that you got from the arp command. There are a few IP address scanner tools that can add on a little extra information and present them in a more attractive format. A good scanner tool should also allow you to save results to a file so you can compare IP address usage over time or reconcile address usage with your DNS server and DHCP server if you get to the point where these functions are managed away from the router.

Most IP address scanners just add a front end to that arp command you tried yourself. An alternative method uses a utility called Ping and runs the command repeatedly to see which addresses respond. This category of software is called a Ping sweep tool.

IP address scanners

If a tool just sweeps the network and lists current addresses, strictly speaking, that is an address scanner. If you have a small network with static IP addresses, then a list of IP addresses currently in use on the network may be all the address tracking you need.

The basic task of scanning for the addresses currently in use is a necessary network management responsibility because it enables you to check for unauthorized connections. Hopefully, your network security system is comprehensive enough that outsiders can’t just connect to it and allocate themselves an unused address. However, just to be sure, periodic scans of the network should be performed. If you operate a system that allows anyone to connect, such as a BYOD wifi router for the private use of employees, then it is advisable to check on the addresses of the devices connected to the network and keep a log of them.

To give you an idea of the type of information you can get from an IP address scanner or a Ping sweep tool, take a look at these two tools:

Angry IP Scanner

Angry IP Scanner

This free IP scanner can be installed on Windows, Linux, and Mac OS. The scanner expects a range of IP addresses as a parameter to the search, but if you just enter a very wide range, you don’t need to worry about seeing a list of unused addresses because the tool will only show addresses that are in use.

The output of a scan shows the IP Address of each device on the network, together with the hostname and the contact response time. You also have the option to see each device’s MAC address and a list of its open ports. Output can be saved to text, CSV, or XML formats.

SolarWinds Ping Sweep (FREE TRIAL)

SolarWinds Ping Sweep

To get a look at how a Ping sweep tool operates you could try out the SolarWinds Ping Sweep function. The tool works on Windows and it has a graphical interface. You need to enter an address range before starting the sweep. The results of a sweep show each IP address in use, the host name of that device and the response time for that node. You can save results in text, CSV, or HTML format.

Unfortunately, this tool is not free. It is part of a very large bundle of more than 60 tools, called the Engineer’s Toolset. The toolset is a bit pricey, but it is packed with all of the network administration tools that you are going to need. You can try out the package in a 14-day free trial.

SolarWinds Engineer's ToolsetDownload FREE Trial at SolarWinds.com

FURTHER READING: 10 Best Ping Sweep Tools and Software

SolarWinds Port Scanner (FREE TOOL)

SolarWinds PortScanner screenshot
SolarWinds Port Scanner is an IP address scanner that allows users to scan IP addresses in their network. Scans can be run through the graphical user interface (GUI) or the command line.

Scans are multithreaded to ensure that IP addresses are found quickly. When running a search you can enter hostnames, IP address ranges, and port ranges to determine what information is displayed on the screen. Once you activate the scan you are then shown a list of IP addresses on the screen.

Next to the IP addresses, you can also view the TCP and UDP points (open, closed and filtered) associated with the IP addresses. In practice, this allows you to check up on the status of these ports to verify that the network is secure.
Being able to check up on IP addresses and port status together allows you to manage your IPs while simultaneously monitoring security vulnerabilities. You can also see the host names, MAC addresses, and operating systems of connected devices.
To make it easier to run subsequent searches, you can save scan configurations. Likewise, once you’ve finished a scan, you can export the results as an XML, CSV, or Excel file. Being able to save configurations and results like this makes running scans and feeding back their results much easier.

As a port scanning solution, SolarWinds Port Scanner is suited to those organizations that need a fast and low maintenance IP scanning solution. The option to use a GUI or command line interface makes this program accessible to users no matter which they prefer. Best of all, SolarWinds Port Scanner is available as a free tool.

SolarWinds Port ScannerDownload 100% FREE Tool

IP Address Tracker tools

One level up from scanning is tracking. An IP tracker will spot when an allocated IP address gets dropped or becomes unresponsive. This situation is very rare on a small network, but once you install a separate DHCP server, dropped or changed IP addresses start to become a big issue. If you try allocating your IP addresses yourself without a server, you are going to end up with duplicate addresses and DNS errors, so things can really get out of hand very quickly without a tracker.

When you think of all of your tasks to administrate your network, the allocation of IP addresses is pretty close to the top of the list. However, few administrators think to keep checking on IP addresses. The lack of tracking capabilities on most networks can spell disaster. You will end up firefighting and trying to work out how two devices ended up with the same IP Address and you will wonder why it is that one part of the network keeps blocking up.

These are address tracking issues that you need to get ahead of. The misallocation of addresses causes a ripple of problems and you may not initially spot the root cause of your network’s traumas. Avoiding network address issues is the first stage of a smarter way to work. Make contention prevention and subnet right-sizing priorities for your network and many of your regular problems will disappear.

Here are two IP address tracker option for you to look into.

SolarWinds IP Tracker (FREE DOWNLOAD)

SolarWinds IP Tracker

SolarWinds gives a much better deal with its IP Tracker than it does with its Ping Sweep tool, because this standalone utility is completely free of charge. The software installs on Windows.

This tool is able to spot IP address misallocation that results in duplications. One shortfall of the service is that it isn’t able to coordinate directly with a DHCP server or a DNS server. However, that functionality is only usually expected from an IP address manager and the SolarWinds IP Address Manager covers all of those duties if that is the type of coverage that interests you.

SolarWinds IP Address ManagerDownload FREE Trial at SolarWinds.com

MyLANViewer

MyLanViewer

MyLANViewer is free to use and runs on Windows. The tool scans the network and then lists all of the devices that it discovered in a GUI interface. The list is organized a little like a Windows Explorer directory structure. Each node in the results list can be expanded to show the device’s IP address, MAC address, operating system, work group, and Ping time.

This tool keeps its eye on the system and will notify you if a new device connects to the network. It can also detect hidden devices and rogue DHCP servers. So, this ongoing monitor of IP addresses acts as a security tool.

FURTHER READING: 10 best IP address tracker tools and software

IP address management (IPAM)

Large networks require IP address management systems to reconcile DHCP and DNS records with the reality of the IP addresses that are actually in use on a network. Network IP scanning is the basic element of IP management. If you are just starting up a new, small network, IP address scanning should be all you need. As your network grows, however, you will need to advance to IP address tracking and on to using an IP address manager.

IP Address Manager (IPAM) tasks are necessary because many devices that have been allocated an address will be switched off or disconnected from the network before their leases expire. In these scenarios, the procedures to relinquish an address are not always completed. So, the DHCP server believes that an address is in use when actually it isn’t. When the device that abandoned an address reconnects, it goes through the address request procedure automatically rather than just continuing with the address that it already had. The IPAM tool should interact with the DHCP server to remove abandoned addresses from the allocation register and make it available in the pool. The IP address manager also needs to interact with the DNS server to update records when IP addresses change.

SolarWinds IP Address Scanner (FREE TRIAL)

SolarWinds IP Address Scanner

SolarWinds produces the IP Address Manager (IPAM), which integrates an IP address scanner. With this package, you get a better IP address tracking facility because it will automate many of the manual processes that you will usually need to go to in order to completely resolve all addressing issues.

A full IP management system needs to integrate with a DHCP server and a DNS server. The DHCP server should check with the IPAM database for available addresses before allocating them. The DNS server’s entries that map between IP addresses and hostnames will become out of date when address leases expire and get replaced by new addresses. This coordination between DHCP, DNS, and IPAM is called “DDI.” The SolarWinds IPAM is a full DDI coordination solution. Although the tool doesn’t include a DHCP server or a DNS server, it will coordinate with those two systems to ensure address compatibility.

The SolarWinds IP Address Scanner combines ICMP Ping and SNMP functions to gather all address related data, including the MAC address and hostname of each node on the network as well as its IP address. The service will run automatically in the background periodically and doesn’t require any manual intervention. The scanner will also update all of the address pools to show newly available addresses and mark all discovered addresses as allocated. The SolarWinds IPAM is able to work with IPv4 and IPv6 addressing

Live reports of IP address sweeps appear in the dashboard for the IPAM. SolarWinds builds its system monitoring tools on a common platform, called Orion. The IPAM is part of that system and so it can easily integrate with other SolarWinds monitoring and management utilities. As with all on premises SolarWinds software, the IPAM installs on Windows Server. You can get the tool on a 30-day free trial.

SolarWinds IP Address ScannerDownload 30-day FREE Trial

ManageEngine OpUtils (FREE TRIAL)

IPAM ManageEngine

ManageEngine has two version of OpUtils, the Free edition and the Professional edition. In many instances, a free version of a tool is the same as the paid product, but with performance limitations; in the case of OpUtils, the two editions contain different utilities.

The Free OpUtils includes the Network Scanner, which checks on each IP address’s connection/usage status. This is the basic requirement for any IP address tracking exercise. The tool offers several scanning options. These are a Ping scan, an SNMP scan, a MAC address scan, and a DNS scan. You need to enter a range or list of IP addresses to scan in order to start the utility, but if you don’t know which addresses are being used by your DHCP server, you can just enter the widest range possible.

The Professional edition of OpUtils bundles together an IPAM solution with a switch port mapper. The IP Address Manager is a much more comprehensive tool that the Network Scanner in the Free edition of OpUtils.

The IPAM is a useful tool for checking on the current usage of IP addresses on your network. It will spot the addresses that are marked as in use in your DHCP server, but are no longer active. This enables abandoned addresses to be returned to the DHCP pool of available addresses.

If you implement subnet addressing on your network, the OpUtils IPAM will warn you of address pool exhaustion. It can also guide you through the process of resizing your subnet sizes to extend network address pool for those network sections that have greater requirements. The tool can interact with and update Microsoft DHCP servers and Active Directory.

OpUtils runs on Windows Server and Linux. You can get a 30-day free trial of the Professional edition of the utility.

ManageEngine OpUtilsDownload 30-day FREE Trial

FURTHER READING: The Definitive Guide to DHCP