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I have a network with several devices connected to it which includes PC's, printers, routers, hubs, access points, etc.

This network was setup using several IP address ranges (for instance: 192.168.0.x for range 1, 192.168.1.x for range 2, and so on) and on some point they connect with each other.

How can I get a list of all IP addresses for all devices connected to the network, assuming I will be connected only to a specific IP address range? I need to get a list of all IP addresses on all IP address ranges.

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Feb 21 '18 at 16:25
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There really is no single way to do this. For your network devices, you should have an IPAM (IP Address Management) database of the assigned addresses, which should be statically assigned for network devices. Some network devices will have multiple addresses. For example, routers need an assigned address for each interface, including virtual/logical interfaces, e.g loopbacks. If you do not have such a listing, you need to connect to each network device to discover the addresses assigned in the devices.

For devices using DHCP, you should be able to get that information from your DHCP server assignments.

For devices with statically configured addresses, you will have more trouble. You can get into each device to see how the addressing is configured. You could look in the ARP table of the router for each device to see the IP/MAC address resolutions, but remember that ARP table entries time out, and the ARP table may be incomplete.

Unfortunately, if you did not keep up with this from the start, this will probably not be easy to create from scratch.

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There's several way to inventory the devices on the network

  • scanning tools, like NMAP can be use to scan all you IP networks and try to gather information about all hosts that respond. This is not 100% accurate since hosts firewall can block the request and so the host may not respond

  • your best bet is to inspect the ARP table of the router(s) that connect those networks together and to the Internet. This will give you the MAC address of all devices that communicated recently along with their IP

  • inspecting the MAC table on the switches will give you only the MAC address of the devices but you will have a better view on how many devices and where they are connected, and you can map this information with the previous methods

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If you can connect directly to each of the segments/VLANs you can use an ARP scan to discover IP addresses (and associated MAC addresses).

Try to ping each IP address but instead of looking at the reply, check the local ARP table instead if there's an entry for the IP address.

This will work regardless of whether a node responds to ping.

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