UPDATE 10/4 6:47 EDT

I have been going through all the comments. THANKS!!! I did not know about the techniques listed, so they are extremely helpful. Sorry for the slow update. As I mentioned below, I got behind with this yesterday so work cut into my evening.

I ran a port scan. The first syntax, -p, brought no joy. The nmap software itself suggested changing to -Pn. That brought an interesting response:

nmap -Pn 1-9999 <Local IP Addr>

Starting Nmap 7.93 ( https://nmap.org ) at 2024-10-04 11:44 BST

Failed to resolve “1-9999”. Nmap scan report for <Local IP Address> Host is up (0.070s latency). All 1000 scanned ports on 192.168.0.46 are in ignored states. Not shown: 990 filtered tcp ports (no-response), 10 filtered tcp ports (host-unreach) Nmap done: 1 IP address (1 host up) scanned in 6.03 seconds Just to be absolutely sure, I turned off my work computer (the only windows box on my network) and reran the same syntax with the same results.

As I read this, there is definitely something on my network running windows that is not showing up on the DHCP.

UPDATE 10/6

I am working through all these suggestions. I am sorry for the slow responses, but I have my hands full with family weekend. I will post more next tomorrow. But I did do one thing that has me scratching my head and wondering if this may be a wild goose chase.

I ran the nmap again per below with a completely fictional IP address within my normal range. It gave the exact same results:

nmap -A -T4 -p- -Pn <Fictional IP>

Starting Nmap 7.93 ( https://nmap.org ) at 2024-10-05 13:36 BST Nmap scan report for <Fictional IP>

Host is up (0.054s latency).

All 65535 scanned ports on <Fictional IP> are in ignored states.

Not shown: 65525 filtered tcp ports (no-response), 10 filtered tcp ports (host-unreach)

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .

Nmap done: 1 IP address (1 host up) scanned in 182.18 seconds

  • r00ty@kbin.life
    8·
    1 month ago

    Hmm. That would mean it’s likely one of the following (well perhaps more options, but these spring to mind)

    • A windows machine that has the network set as a public network, or netbios specifically blocked on LAN.
    • A windows machine that has all the netbios services disabled.
    • Not a windows machine, or a container as others suggested that’s running some kind of IIS install
    • Not a windows machine at all but for some weird reason IIS files and a web server setup.

    I think you suggested in another comment, that it’s not in your DHCP client list but has an IP in your normal range. Which suggests it is setup with a static IP. That is odd.

    Some other people suggested it could be a container that is using a real IP rather than the NAT that docker etc usually use. I do know that you can use real IPs in containers, I’ve done it on my NAS to get a “proper” linux install on top of the NAS lite linux that is provided. But I would have expected that you’d know about that, since it would require someone to actually choose the IP address to use.

    If you have managed switches you could find which port on which switch the MAC address (as found by lookuping up the arp record for the IP using arp -a) is on (provided the switch allows access to the forwarding tables). Of course, if they’re on Wi-Fi it’s only going to lead to the access point they’re connecting to.