Configuring routing on OPNsense to communicate with Cisco devices

[Elhanan]

Hello friends
I am having a hard time configuring an OPNsense to accept traffic on LAN Interface and forward them to the WAN interface. It's been a month since I started trying to set up OPNsense, please help me out.
Here is a network structure



I wanted to route traffic to the OPNsense server from Cisco Switch 3850, specifically, VLAN 22-based traffic from Cisco Switch to 3850, and then I want to send the traffic from the OPNsense server to Cisco ASA which is a gateway for my Network.
Can someone please guide me with this setup? I tried policy-based routing on Cisco Switch 3850 and couldn't reach the OPNsense server to configure it through the web.

Thank you.

[lilsense]

from quick look and since there's no config provided, there's no VLAN communication and all are IP routing. So not sure what you are asking here...

[Elhanan]

@lilsense Thanks for replying

I am afraid that I might over-explain the structure of my network,

Currently:

Cisco 3850 Switch is inter routing the VLANs and is directly connected to the Cisco ASA Firewall (Via OSPF) and connected to Cisco Router (Used static route). I am not using OPNsense for all traffic right now. The current connection of those devices (Cisco Switch, Router, and ASA) is denoted with a dotted line.

What am trying to achieve
I wanted to add an OPNsense device in between Cisco Switch and the Other two Cisco Devices (ASA, Cisco Router)
Since I don't want to interrupt the current network I only wanted to test OPNsense with VLAN 22 which is configured on Cisco 3850 and my laptop is on VLAN 22.

What I have tried so far
I used Policy Based Routing on Cisco 3850 switch to send traffic sourced from VLAN 22 to be forwarded to the OPNsense Interface. The moment I applied that I couldn't connect to the OPNsense web admin. Therefore should I do another routing on OPNsense to forward traffics back to Cisco Switch 3850?

[lilsense]

you cannot do what you are attempting to do as you are trying to forward 22.0 traffic to 18.0 but 18.0 does not know where to go... I think you are trying to create a "router-on-a-stick" but it's not complete.

why not just use the Opnsense as your 22.1 default gateway. set the 3850 ports to be vlan 22.

[Elhanan]

Hello @lilsense
Actually, the Cisco Switch 3850 is doing inter-vlan routing already, so that's not a problem for now. I wanted to use Policy Based Routing on this Switch to route VLAN 22 traffic to OPNsense and then do another config on OPNsense to forward those traffic to my ASA Firewall, which helps to out into the Internet.

What is confusing is how I set routing on OPNsense to forward back traffic to VLAN 22 on Cisco 3850, secondly, I am thinking to use OSPF between the ASA and OPNsense, since OPNsense will be connected to both ASA and Cisco Router in the future.