rras vpn connection error !

Question

rras vpn connection error !

Sanna Kor 40

May i know if anyone here has experienced remote users connecting to an rras vpn and getting error 789, where the l2tp connection attempt fails because the security layer encounters a processing error? this seems to happen randomly, and i’m trying to figure out whether it’s caused by a pre‑shared key (psk) mismatch or an ipsec service dependency issue.

I've already checked the vpn configuration and confirmed that the psk matches on both the client and server sides, but the error still appears. could it be related to the ipsec policy service not starting correctly, or maybe a missing registry entry under HKLM\SYSTEM\CurrentControlSet\Services\PolicyAgent ?

If anyone has dealt with this before, how did you verify the psk consistency and ensure all ipsec dependencies were running properly ?

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Answer 1

Hello,

Error 789 with L2TP/IPsec on RRAS almost always points to an IPsec negotiation failure rather than a simple PSK mismatch. Since you’ve already confirmed the pre‑shared key is consistent on both sides, the next place to look is the IPsec service stack and its dependencies. The “IPsec Policy Agent” service (PolicyAgent) must be running, and it depends on the Base Filtering Engine (BFE). If BFE is stopped or misconfigured, PolicyAgent will fail silently and you’ll see intermittent 789 errors. Verify in services.msc that both BFE and PolicyAgent are set to Automatic and are running.

Additionally, check the registry under HKLM\SYSTEM\CurrentControlSet\Services\PolicyAgent and confirm the Start value is set to 2 (Automatic). If it’s set to 4 (Disabled), the service won’t start even if you try manually. Another common cause is NAT‑Traversal issues: if the RRAS server is behind NAT, ensure UDP 500 and UDP 4500 are open and not being filtered. Sporadic failures often indicate that one of these ports is intermittently blocked or subject to inspection by a firewall.

To verify PSK consistency beyond just retyping, you can use the RRAS console: open the VPN server properties, go to Security, and re‑enter the PSK. On the client side, delete and recreate the VPN connection to flush any cached credentials. If you want to confirm IPsec negotiation, enable logging by setting the registry key HKLM\SYSTEM\CurrentControlSet\Services\RasMan\Parameters\Logging to 1, then check %windir%\tracing\rasman.log and %windir%\tracing\ipsec.log. These logs will show whether the PSK was rejected or if the failure occurred earlier in the negotiation.

If after confirming services, registry values, and firewall ports the error persists randomly, it’s worth checking whether the Windows Filtering Platform is applying conflicting IPsec policies. Run netsh ipsec dynamic show all to see active policies. A stale or conflicting policy can cause intermittent drops. Clearing them with netsh ipsec dynamic delete all and restarting PolicyAgent can stabilize the connection.

I hope you've found something useful here. If it helps you get more insight into the issue, it's appreciated to accept the answer. Should you have more questions, feel free to leave a message. Have a nice day!

HL.

Answer 2

Error 789 means the L2TP/IPsec security layer hit a processing error during the initial security negotiation with the remote computer.

Based on the available guidance, the most relevant checks are:

Confirm whether the failure happens before credentials are prompted.
- If the connection fails before the username/password prompt appears, the IPsec session was not established.
- In that case, the problem is in the IPsec phase, not PPP authentication.
Re-check certificate or pre-shared key configuration.
- A common L2TP/IPsec configuration failure is a misconfigured or missing certificate or a misconfigured or missing pre-shared key.
- Error 789 specifically maps to: “The L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer.”
- A PSK issue is also separately represented by RRAS error 811, which is described as typically caused by a pre-shared key problem between client and server.
Review RRAS and client event logs.
- On RRAS, check system error events for the RemoteAccess service:
```
     Get-EventLog -LogName System -EntryType Error -Source RemoteAccess | Format-List -Property *
```
- Also check client connection attempts in the Application log from RasClient:
```
     Get-EventLog -LogName Application -Source RasClient | Format-List -Property *
```
- The documented examples call out two common causes visible in logs:
  - incorrect IP address configured for the VPN gateway/interface
  - wrong shared key configured
Distinguish 789 from related L2TP/IPsec errors.
- 786: no valid machine certificate on the client
- 787: security layer could not authenticate the remote computer
- 788: security layer could not negotiate compatible parameters
- 789: processing error during initial negotiations
- 790: certificate validation on the remote computer failed
- 791: security policy for the connection was not found
- 792: security negotiation timed out
- 793: error occurred while negotiating security
If the issue is random, focus on negotiation-stage causes.
- Since the PSK was already verified, use the event logs to determine whether the failures align more with:
  - intermittent security negotiation failures
  - certificate validation problems
  - timeout conditions
  - wrong shared key being used by a specific client or interface profile

The provided material supports checking PSK/certificate configuration and RRAS/RasClient logs. It does not provide confirmation that a missing PolicyAgent registry entry is a known cause for error 789, and it does not document IPsec service dependency validation steps for this specific error.

References: