In what I would consider a pretty standard router setup with a bridged LAN with DHCP and a single WAN connection, here is what I am seeing:
I previously had a computer (Computer A) sitting on DCHP Static LAN IP 192.168.10.2. It worked great for many months on that IP. I changed the DHCP Static LAN IP assignment from 192.168.10.2 to 192.168.10.3 and I forced the refresh at the computer. This worked. I can ping the computer on that address. I can connect to it via Remote Desktop. I can ping out. So changing that computer from .2 to .3 worked fine as expected. Computer A is happy/good.
I had a NEW computer (Computer B) that had been given some dhcp assigned ip like .4 I made the DHCP entry Static and changed it to 192.168.10.2. I forced the refresh. The new computer (Computer B) now has an address of .2 BUT it cannot ping out. I can’t ping the gateway (192.168.10.1). I can’t ping a DNS like 1.1.1.1.
Oddly enough, I am able to connect to the new computer using Remote Desktop. I am able to ping the new computer from another system (Computer C) can ping 192.168.10.2 just fine and connects to it. I cannot connect from B to C though, which is baffling since I’m getting some kind of traffic.
So when Computer B has:
DHCP Static LAN IP: 192.168.10.4
Assigned to MAC: F4:E9:09:2E:BD:32
I can ping out from Computer B, no problem. This is also true when I let DHCP assign a LAN IP instead of me setting it to static. Internet access on Computer B is “normal” in these conditions.
When Computer B has:
DHCP Static LAN IP: 192.168.10.2
then I am not able to ping out from Computer B, but I can remote desktop connect from Computer C over to Computer B with no problems. The moment I try to put Computer B onto .2 IP, the weird behavior I have explained presents itself. I cannot ping out from Computer B to anywhere local or otherwise, but I can connect to Computer B from other computers on the LAN.
Windows 10 of course reports that there is no network connectivity because it can’t ping anything. I have tried disabling the Windows Defender Firewall completely. This doesn’t change the situation at all.
I think there is something in the router with 192.168.10.2 that is “stuck” with the old computer. My old computer had been statically set to 192.168.10.2 for a long time. However the old computer is working fine on .3.
I’m baffled at this point. I would have blamed the firewall, but the behavior is the same with the firewall on or off. .2 is not in use by any other computer. I have tried putting .2 onto a third computer and the third computer exhibits the same odd / bad behavior of not being able to ping out / no internet access. So, I’m pretty sure this is something happening on the router. I’ve been all through Winbox and I don’t see anything in it that would cause this. I’ve rebooted the router several times, but that doesn’t change anything.
I really don’t want to wipe out my routeros and start all over. I have a number of other basic things working very well on it. (Other static IP assignments are fine. Static DNS entries, Open VPN, port forwards, upnp, and other stuff… things that took me a long time to get setup the way I want them as I had to figure them out.)
Any thoughts on things I can check? It seems like there is something “stuck” in the router regarding the .2 address specifically.