RPC_S_BINDING_HAS_NO_AUTH (0X000006D2) fix — real world steps

What actually causes 0X000006D2

This error means the RPC runtime has no authentication info for the binding. In plain English: the client and server aren't talking securely. I've seen this pop up in two main scenarios — after a Windows update that hoses the RPC service, or when a domain controller's clock drifts more than 5 minutes from the rest of the domain. Had a client last month whose print queue died completely across twenty workstations because of this exact error. Let's cut to the chase.

Cause #1: Broken RPC service after a Windows update

The most common trigger. Windows updates (especially cumulative ones) can corrupt the RPC endpoint mapper or the RPC Locator service. The error shows up in Event Viewer under System with source 'RPC' and event ID 100. You'll see it when trying to connect to a remote admin share or run a PowerShell command against another machine.

Fix: Restart and re-register the RPC services

Open an admin PowerShell or Command Prompt.
Run:
```
net stop RpcSs && net stop RpcLocator
```
Then restart them:
```
net start RpcSs && net start RpcLocator
```
Re-register the RPC endpoint mapper:
```
regsvr32 /s rpcrt4.dll
```
Reboot both machines (client and server).

If that doesn't stick, check the RPC service dependencies. Open services.msc, find 'Remote Procedure Call (RPC)', double-click it. Under the 'Dependencies' tab, make sure 'DCOM Server Process Launcher' and 'RPC Endpoint Mapper' are both running. If the Endpoint Mapper is stopped, set it to Automatic and start it. I once spent two hours on this because a GPO had disabled the Endpoint Mapper. Don't be me.

Pro tip: After a Windows update, always check if rpcss.dll got replaced. Run sfc /scannow from an admin prompt to fix any corruption. I've seen this resolve the error in 15 minutes flat.

Cause #2: Clock drift on the domain controller

Kerberos authentication uses time stamps. If the domain controller's clock is off by more than 5 minutes (the default tolerance), RPC bindings fail with this error. The fix is time sync — but not just any sync. You need to force the DC to sync with an external time source.

Fix: Force NTP sync on the DC

Identify if your DC is the PDCe emulator:
```
netdom query fsmo
```

On the PDCe, run as admin:

w32tm /config /manualpeerlist:time.windows.com /syncfromflags:manual /reliable:yes /update

Then force sync:
```
w32tm /resync
```

On all other DCs, sync from the PDCe:

w32tm /config /syncfromflags:domhier /update && w32tm /resync

Check the status:
```
w32tm /query /status
```

If the DC still won't sync, the Windows Time service might be misconfigured. Set it to start automatically and restart it:

sc config w32time start= auto && net stop w32time && net start w32time

Had one client whose DC was running in a VM with time sync disabled. The host clock drifted by 12 minutes. Once I pointed the DC to time.windows.com and enabled host time sync, error vanished.

Cause #3: Misconfigured RPC dynamic port range

Less common, but when it hits, it's nasty. The RPC Endpoint Mapper uses port 135, but dynamic RPC ports (usually 49152-65535) get blocked by firewalls. This error can show as 0X000006D2 on the client side even though the real issue is a port block.

Fix: Check and configure RPC port range

On the server, open an admin Command Prompt and check current port range:
```
netsh int ipv4 show dynamicport tcp
```

If it's not the default, reset it:

netsh int ipv4 set dynamicport tcp start=49152 num=16384

Add firewall rules for these ports on both machines. In Windows Firewall with Advanced Security, create inbound rules for TCP ports 49152-65535. Or if you're old-school, use:
```
netsh advfirewall firewall add rule name="RPC Dynamic Ports" dir=in action=allow protocol=TCP localport=49152-65535
```
Reboot the server.

I also check the RPC Endpoint Mapper's own port. Run rpccfg /show on the server. If it's set to anything other than the default (port 135), change it back. Had a paranoid security admin who moved it to port 4444 — broke everything.

Quick reference summary table

Cause	Symptom	Fix	Time to fix
Corrupted RPC service	Event ID 100, apps fail after an update	Restart RpcSs, re-register rpcrt4.dll, sfc /scannow	15 minutes
Clock drift on DC	Time difference > 5 minutes	Force NTP sync, w32tm /resync	10 minutes
Blocked RPC ports	Error only from certain clients	Check dynamic port range, add firewall rules	20 minutes

Most of the time, it's cause #1. Don't overthink it. But if you've patched recently and the RPC service won't start, check the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RpcSs — make sure the Start value is 2 (Automatic). Seen that get mangled by a bad update once. If none of this works, you're looking at a deeper issue like a damaged OS image or a domain trust problem. But start here.