I have isolated this to be a firewall issue, not Windows DCOM as is a common issue with OPC connections (had that struggle already!) I tested by setting IP of OPC PC to same subnet as MWTP-VLAN and bypassed firewall. I get the error 'The RPC server is unavailable' A PC on VLAN-MWTP can ping and rdp to the VLAN-OPC server PC using NATed 192.168.50.32 (translates to 192.168.77.4), but it seems it cannot browse or connect to the OPC server. VLAN-OPC can access the VLAN-AWTP ok (can access TCP port on industrial device). Here's my current state of affairs and my issue: This involves NATing and such which I think I have implemented ok. The purpose of the firewall is to give VLAN-MWTP access to a PC on VLAN-OPC (FULL access is ok), and give limited access (single TCP port) from the OPC server to the industrial device. Outside IP range (VLAN-MWTP): 192.168.50.xxx (OPC client) Inside IP range (VLAN-AWTP): (industrial devices)ĭMZ IP range (VLAN-OPC): 192.168.77.xxx (only has OPC Server PC which accesses an industrial network device)

I am integrating a Cisco ASA 5505 firewall in the following manner:

Cisco 5505 asa firewall