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I have a network switch and I don't know its ip nor mac address nor even subnet. I need to get all this information.

Yes, there are tools like nmap and arp-scan, but the problem is they all need an ip address or subnet to work.

How can I discover which mac/ip/subnet my switch is using?

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You can access it via Serial port or Console cable. But you need to know username and Password. But it should be a manageable switch.

Generally switch has no ip address and if it has ip address that mean it should be in device management vlan. Firstly check your device management vlan ip address range.

You can find mac address using IP scanner tool. Most IPscanner tools are shows switch mac address with devices ip address. This process will be time consuming because you have no idea about subnet or ip address range.

If it is in vlan and if it is connected with another switch such as core switch you can find it within core switch. In cisco you can use 'show cdp nei detail' command.

If it is not a manageable switch don't think about ip address or subnet.....

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  • So, there are no L2 protocols (excluding proprietary) which broadcast and say "Hey all hosts, send me your MAC addresses" or something? Except for arp/icmp made for every possible ip address. Dec 4 '19 at 11:18
  • what is your product model?
    – infra
    Dec 4 '19 at 11:45
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    If your switch is unmanaged, it does not have an IP address.
    – Teun Vink
    Dec 4 '19 at 12:11
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    ... nor MAC address.
    – Zac67
    Dec 4 '19 at 15:43
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    @OlegYablokov insulting people who are trying to help you isn't beneficial. If more than one person answers something different than what you're looking for, you should consider improving your question instead.
    – Teun Vink
    Dec 5 '19 at 6:20
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If you have access to the switch the unknown switch is connected to, use "Show LLDP nei" (Cisco command), this will list all the MACs the switch is talking with. (On Cisco, you might have to enable LLDP first. Enter "LLDP run" in config mode.)

Then put on your deerstalker cap and eliminate all known MACs. By process of deduction, the (hopefully) last unknown MAC should be your target.

Also, use a website like "MAC Vendor Lookup" to help ID and eliminate your "known MACs.

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