We are using MSDTC for SQL transactions. I am having issue with setting up firewall for MSDTC to work. The application and SQL are running on separate machine. Currently MSDTC is working if i turn off firewall on application server. I think there should be someway to add exception to the firewall setting for some ports. So that firewall can still be ON and DTC will not have any issues. I am not sure of the ports to add in firewall setting (I did try adding port 135 with no success)
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Have your Firewall allow port 135 and the dcom port range. By default, the dcom port range is 1024-65535. Thats a big range to open up. You can limit this range in the registry or using dcomcnfg. This post describes this:

Matt Wrock
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3This answer is ancient and Microsoft now has a better way if you are using Windows Firewall. There are default rulesets for "Distributed Transaction Coordinator". You can enable those based on the "Domain" or "Public/Private" profiles. They include "RPC-EPMAP", "RPC", and "TCP-in". – duct_tape_coder Aug 25 '20 at 15:48