How to Fix: VPNC cisco + quick mode response rejected error

The VPNC error 'quick mode response rejected: (ISAKMP_N_INVALID_PAYLOAD_TYPE)(1)' occurs when the Cisco concentrator rejects the payload type used by VPNC, preventing it from establishing a connection. This issue affects users who try to connect to Cisco gateways using VPNC.

This error can be frustrating for users as it prevents them from accessing company resources remotely. However, there are steps that can be taken to resolve this issue and establish a successful connection.

💡 Why You Are Getting This Error

• The primary reason for this error is that the Cisco concentrator may be configured to require IP compression, which is not yet supported by VPNC. This configuration is intended as an additional security measure but can lock out even Cisco clients on non-Windows platforms.
• Another possible cause is that the concentrator is configured to require a firewall, which can also block connections from Cisco clients.

🚀 How to Resolve This Issue

✨ Wrapping Up

To resolve the 'quick mode response rejected: (ISAKMP_N_INVALID_PAYLOAD_TYPE)(1)' error when connecting to Cisco gateways using VPNC, it is recommended to enable NAT traversal mode or configure IP compression to disable. By following these steps and consulting with the administrator of the Cisco concentrator if necessary, users can establish a successful connection and access company resources remotely.