Connection Timed Out when trying to access Proxmox's Web Gui/SSH

[TotesFab]

Hi,

I switched out my old USG for OPNsense (micro PC) a week ago.  The other day I installed Proxmox on a server  and could not access the web gui nor SSH to it,  I would just get time out errors.  When I try to curl to it, the response is also blank.  I got frustrated after reading through a bunch of threads so I plugged my USG back in.  Instantly, everything worked.  I was able to connect and use the Web Gui.  So for the next day I set up a bunch of apps (Plex, Omada, Home Assistant, Syncthing, etc).

Yesterday, my USG started to die again (power problems) so I was forced to swap back to OPNsense (I like it, and want to learn it).  Again, I cannot connect to it as I just get connection timed out errors.  That said, I can access all the other web apps that I installed on Proxmox (Home assistant, syncthing, etc).  I have read so many threads that lead me down wrong paths that I don't think its worth me going over the things I tried...I'd rather start over.

OPNsense: 192.168.1.1
Proxmox (static): 192.168.1.111/32

1. Proxmox can access the internet (I can curl from it).  Also, when I do tcpdump, I can see my PC trying to connect to it.  I can also ping Proxmox from my PC and vice versa.

2. I have already tried setting the OPNsense firewall to Conservative and set "Disable firewall on the same interface".  Those options had no affect so I set them back to default after.

3.  I can access the web apps installed on Proxmox

4. I time out regardless of device and browser. Even curl just gives a blank response.

Please, any help or suggestions would be great. Thank you!

[dseven]

Where are you trying to access it from?

Your proxmox interface probably should be configured as 192.168.1.111/24, not /32, but I don't know how it would work with your USG in th picture if that was the issue.

[TotesFab]

So...umm...that worked. But I don't understand why.  Originally I had it as /27 (worked with USG) and when it wasn't working I changed it to /32.  Why did /24 work?

I thought I was just giving a static IP to the server so I figured it just needed a single IP.  Sorry, I need to relearn networking now lol.

[dseven]

A refresher on networking basics would probably be good. I don't have a particular one to recommend, but Google finds lots.

Basically the subnet mask specifies the size of the subnet. Hosts on the same subnet can talk to eachother without passing through a gateway (router/firewall). If you configure the interface with a /32 address, it shouldn't be able to talk to anything other than itself. I'm still not entirely sure how it was working with your USG. Probably traffic between your client and proxmox was "hairpinning" through the USG.

The subnet mask on your proxmox interface should match that on your firewall's LAN interface. I'd recommend /24 for private LAN subnets (such as 192.168.1.0/24), as that's the default and the easiest to work with.

[TotesFab]

THANK YOU.  That makes so much sense.  I'm getting flashbacks of setting static IPs in Windows as a kid and following instructions...255.255.255.0 is now flashing over and over in my brain lol!