Installation & Licensing Center
HOW TO - Test If Ansys Is Blocked by the Windows Firewall on a Client Computer
Authored by Caleb Scharf
November 1st, 2026
17605 views
7 likes
KB994568
Description
The Windows Firewall on an Ansys client computer can sometimes stop Ansys from running properly. This is most common with Fluent and its MPI (Message Passing Interface) programs, which use the network. It can also happen on computers that use Ansys Remote Solve Manager (RSM).
This article helps you test whether the Windows Firewall is causing the problem. It then shows you how to allow the Ansys programs the firewall blocks.
The firewall can block a program in two cases. The first is when Windows asks you to allow the program through the firewall and you select "Cancel". The second is when you are not a local administrator on your computer.
Note: A blocked program does not always cause errors. It depends on which program the firewall blocks.
Client Computer, Not License Server
This article covers the computer where the Ansys client software is installed, not the license server. For the license server, see HOW TO - Add Firewall & Port Exceptions for Ansys License Manager.
Solution
1. Test If the Firewall Is the Cause
- Open the Windows Start menu, search for Windows Defender Firewall, and open it.
- Click Turn Windows Defender Firewall on or off.
- In every network section, select Turn off Windows Defender Firewall (not recommended), then click OK.
- Try to reproduce the error in Ansys.
- If the error still happens, the Windows Firewall is not the cause.
- If the error does not happen, the Windows Firewall is the cause.
- Turn the firewall back on: repeat steps 1 to 3, but select Turn on Windows Defender Firewall in every network section.
Note: Skip the rest of this article if the error still happened in step 4. The Windows Firewall is not the cause.
2. Allow the Blocked Ansys Program
- Open the Windows Start menu, search for Windows Defender Firewall with Advanced Security, and open it.
- In the left pane, select Inbound Rules.
- Click the Program column heading to sort the rules by program path.
- Look for blocked rules for programs in these folders:
C:\Program Files\ANSYS IncC:\Program Files\AnsysEM
Note: The picture below shows examples of blocked Ansys programs.
MPI Programs Are Often Blocked
Client firewall rules often block MPI programs, and Ansys shows errors when they are blocked. Some MPI programs are in C:\Program Files\ANSYS Inc\vXXX\commonfiles\MPI\..., where vXXX is your Ansys version folder. Others are in each Ansys product's folder, such as lsdyna_mpp_dp_msmpi.exe and fl_mpi2110.exe.
- Right-click a blocked Ansys rule, then click Properties.
- Select Allow the connection, then click OK. Repeat steps 5 and 6 for each blocked Ansys rule.
3. Verify It Worked
- With the Windows Defender Firewall turned on, try the Ansys task that produced the error again. If it runs without the error, you are done.
- If the error comes back, return to Inbound Rules and allow any other blocked Ansys rules, including the MPI programs listed above.
