RPC_NT_PROTOCOL_ERROR 0XC002001D Fix – Quick & Dirty

What’s This Error and When Does It Hit?

You’re working on a Windows Server or a client machine, and boom—RPC_NT_PROTOCOL_ERROR (0XC002001D). It pops up when you try to connect to a remote computer, access a network resource, or run a backup job. I saw it last month on a small law firm’s file server running Windows Server 2019. Their overnight backup kept failing, and no one could map drives from the accounting department.

This error means the Remote Procedure Call (RPC) service is either blocked, broken, or misconfigured. It’s a communication failure between two machines. Don’t overthink it—most fixes are fast.

Fix 1: Quick Check – Firewall Rules (30 seconds)

Nine times out of ten, this error is a firewall. Windows Defender Firewall or a third-party one like Norton or McAfee sniffs the RPC port range and blocks it. I’ve seen it happen after a Windows update reset the firewall rules.

1. Disable the firewall temporarily – On the machine getting the error, open Control Panel > Windows Defender Firewall > Turn Windows Defender Firewall on or off. Set both private and public to “Turn off.”
2. Retry the operation – If the error disappears, the firewall’s the problem.
3. Re-enable the firewall – Don’t leave it off. Add an exception for RPC:

Open Windows Defender Firewall > Advanced settings > Inbound Rules > New Rule
Rule type: Port
Protocol: TCP
Specific local ports: 135, 49152-65535
Action: Allow the connection
Profile: Domain, Private, Public
Name: RPC Exception

RPC uses port 135 for the endpoint mapper, then a dynamic range (49152-65535 on modern Windows) for actual communication. That range is why the firewall blocks it—apps can’t predict every port.

If you’re using a third-party firewall, check its logs. I had a client whose McAfee silently blocked RPC after an update. Took me 30 minutes to find it, but disabling it for 10 seconds confirmed the culprit.

Still broken? Move to Fix 2.

Fix 2: RPC Service – Restart and Dependencies (5 minutes)

Windows has a few RPC-related services that must be running. If one stops, you get this error. Happened to a buddy’s SBS 2011 server after a bad patch—the RPC Endpoint Mapper service just died.

1. Open Services – Press Win+R, type services.msc, hit Enter.
2. Check these four services are all running (status should be “Running,” startup type “Automatic”):
   • Remote Procedure Call (RPC)
   • RPC Endpoint Mapper
   • DCOM Server Process Launcher
   • RPC Locator (if present – rare on modern Windows, but check)
3. Restart them in order – Right-click each > Restart. Start with RPC Endpoint Mapper, then Remote Procedure Call, then DCOM.
4. Set startup type – For each, right-click > Properties > Startup type: Automatic.

After restarting, try your operation again. If it works, you’re done. If not, check the dependency chain: Remote Procedure Call service depends on RPC Endpoint Mapper and DCOM. If one is stuck, the whole stack fails.

I’ve also seen corrupt service entries—rare but real. Run this command in an admin command prompt to re-register the RPC components:

REG ADD "HKLM\SYSTEM\CurrentControlSet\Services\RpcSs" /v "Start" /t REG_DWORD /d 2 /f
REG ADD "HKLM\SYSTEM\CurrentControlSet\Services\RpcEptMapper" /v "Start" /t REG_DWORD /d 2 /f
net start RpcSs
net start RpcEptMapper

Still failing? Time for the deep dive.

Fix 3: DCOM Permissions and Group Policy (15+ minutes)

This is the ugly one. DCOM (Distributed COM) permissions control who can launch RPC calls. If they’re messed up—often by a Group Policy or a security template—the error persists. I once spent two hours on a client’s domain controller where an overzealous admin had locked down DCOM for “security.”

1. Open DCOM Configuration – Press Win+R, type dcomcnfg, hit Enter. Expand Component Services > Computers > My Computer, right-click My Computer > Properties.
2. Check the COM Security tab – Under “Access Permissions” and “Launch and Activation Permissions,” click Edit Limits. Ensure the following groups are present with Allow permissions:
   • Administrators – Local Access, Remote Access
   • Everyone – Local Access (only – remote access is a security risk)
   • NETWORK – Remote Access, Local Access
   • SYSTEM – Full control
3. Fix if missing – Add them. For “Everyone,” I’d only allow Local Access to avoid exposing your box to internet pings.
4. Check Group Policy – Run gpedit.msc (or rsop.msc). Navigate to Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options. Look for “DCOM: Machine Access Restrictions” and “DCOM: Machine Launch Restrictions.” If these are configured, they override DCOMcnfg. Set them to “Not Defined” or ensure they include the same groups.

After any DCOM changes, restart the RPC services again (Fix 2) and test.

Still no luck? Check the Event Viewer (Applications and Services Logs > Microsoft > Windows > DCOM). Look for error ID 10005 or 10009—those point directly to permission failures. I’ve seen a misconfigured “Everyone” group that allowed only local access block a remote backup completely.

When All Else Fails – The Nuclear Option

If you’ve tried all three and the error persists, you’ve got deeper issues: corrupt system files, a misapplied security policy, or a third-party app that hogs the RPC port. Run sfc /scannow and dism /online /cleanup-image /restorehealth from an admin command prompt. Then reboot. If still broken, consider a system restore to before the error started. I’ve had to do that twice in 10 years—once after a rogue Windows 10 update.

Pro tip: Log the exact time the error first appeared. Check the Windows Update history or installed software dates. Roll back the last change if you can. That’s saved me hours more than any registry hack.