@misinthe said in Issues with Subnet behind UDM Pro:
It was just the internal networks on the pfSense weren't able to go through the UDMP.
Most likely because the UDMP was still natting, and to get behind you would have had to setup port forwarding on the UDMP, etc.
If your going to use the pfsense LAN as transit network to downstream router, please do not put any devices on this network - or your going to run into asymmetrical traffic flow. Whenever you connect 2 or more routers together, especially if they can firewall devices on this "transit" network between routers are going to have asymmetrical flow unless you route on each of these hosts to which router to go to get to specific networks..
If the downstream router does not nat you will most likely see the problem with downstream network trying to talk to devices on the transit..
You run into this problem..
ass.jpg
Pfsense never saw the SYN, so a SYN,ACK going to be block.. If your going to setup routers that talk to each other and route between networks they are attached to.. Setup a transit network.. See this diagram.
pfsense-layer-3-switch.png