Routers Error Code
Systems & Devices
Routers
Error 789 | L2TP connection failed
Industry
Systems & Devices
Canonical
/systems/routers/error-codes/error-789/
Last Updated
Feb 27, 2026
Summary
An L2TP/IPsec VPN connection could not be established due to negotiation or authentication failure.
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What This Code Means
Error 789 is commonly associated with L2TP/IPsec VPN failures where the security negotiation cannot complete. The failure can be caused by missing/incorrect certificates or pre-shared keys, blocked ports, or policy mismatches.
Where Users Usually See This Code
- Windows VPN connection attempts
- Remote access VPN setups behind NAT/firewalls
Why This Code Appears
- Incorrect VPN credentials or shared secret
- Blocked IPsec/L2TP ports by firewall or ISP
- Certificate or policy mismatch
What Typically Happens Next
- The VPN session fails and no tunnel is created
What This Code Is Not
- It is not a Wi-Fi-only issue
- It is not a generic “DNS failed” error
Troubleshooting Checklist
- □ Confirm the VPN type and authentication method with your admin/provider
- □ Verify required ports and IPsec policies are allowed on the network
- □ Check whether the environment requires NAT-T and that it’s supported
Notes And Edge Cases
Corporate networks may block IPsec/L2TP; testing from a different network can help isolate policy blocks.
Related Codes
8 links
- Error 806 CodeVPN connection failed
- Error 809 CodeVPN tunnel could not be established
- Error 772 CodeDial-up failed
- Error 651 CodeConnection failed
- Error 812 CodeConnection blocked by policy
- Error 807 CodeNetwork connection interrupted
- Error 691 CodeAccess denied
- Error 720 CodePPP control failed
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