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
Yeah, that’s a company server, specifically for the local network group
Why would an internal server change IP all the time? DHCP is for silly things like laptops that turn on and off eleventy times a day
Even if it isn’t changing IP, you still want it in your DHCP table so that IP doesn’t accidentally get assigned to something else. It’s unlikely on a small network but it can happen.
Thanks! I did not know DHCP allocation was optional on a home network.
“home” isn’t descriptive enough. you can run some VERY powerful, in depth stuff if you were so inclined on a “home” network.
It is more than your average home network. I have a dual WAN router with fiber on each to a different provider. (It is stupid overkill, but my wife and I both work from home and it is important not to be down). I use a pi-hole for ad blocking and unbound for recursive DNS resolution. Most of the devices are wired Ethernet, so I have a bunch of switches and kit to transform coax into fast Ethernet.
I don’t mess with the firewalls, because that seems like there is a big downside to messing about if you get it wrong. That is all vanilla out of the box.
nice. firewalls are easy though, most you can keep vanilla. if you’ve setup a pihole, configuring a firewall is a breeze. most are all in ones also, so the router/gateway/firewall is all one box, just plug in your modem, then it’s a big switch basically with lots of options.
I run a ubiquiti usg pro 4, first gen and have a 24 port ubiquiti switch and access points. I love it. super advanced users will complain about some things, but ultimately it’s perfectly fine for me without having to get meraki $tuff. I run a few small game servers, a seedbox and some vms, nothing crazy. it moves about 1 TB / day of data from various torrents and nzbs, soulseek. have a micro Dell PC setup as my DNS and pihole, Plex server thousands of movies/shows.