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Cisco Bug: CSCvs64221 - VPN tunnel cannot connect on Windows10 build 1909 with ECDH group 21 and TLS 1.0 disabled on gateway

Last Modified

May 09, 2020

Products (1)

  • Cisco AnyConnect Secure Mobility Client

Known Affected Releases

4.7(4056) 4.8(1090)

Description (partial)

Symptom:
AnyConnect VPN doesn't work on the Windows10 Version 1909

Below error is being displayed once connection fail:
Could not connect to server. Please verify Internet connectivity and server address.

Conditions:
- OS: Windows10 Version 1909 -> current version of OS can be checked using winver command in cmd
- TLS 1.0 is not supported by ASA/FTD -> ssl server-version1.1 or ssl server-version1.2 is configured- 
- Elliptical Curve Diffie-Hellman Group 21 is configured on the head end -> ssl ecdh-group group21
- AnyConnect and the head end negotiate an Elliptic Curve Diffie-Hellman Ephemeral (ECDHE) cipher suite during the initial TLS v1.2 handshake.
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