VPN IPSEC bytes received 0

[INT1]

it happened after a windows update i think im not sure about it i tried unistalling the updates but its still not working what can be the issue?

[INT1]

yes its enabled

[sjoshi]

can you check if IPV6 is enable in the network adapter(disabling IPv6 on the FortiClient SSL VPN virtual network adapter.). then please disable it..also try checking with FCT v7.2.4

[INT1]

does 7.2.4 have IPSEC VPN?

[sjoshi]

yes it is available, but before that can you check if IPV6 is enable in the network adapter(disabling IPv6 on the FortiClient SSL VPN virtual network adapter.)

[link470]

@INT1- did you ever get this figured out?  I'm experiencing the exact same problem with a couple machines.  Both Windows 11, both running FortiClient VPN 7.4.1, connecting via IKEv2 IPSec.  They were previously working, now they're not.  No changes have been made on the FortiGate config or on the FortiClient VPN config. 

The connection establishes and shows connected, and on the FortiGate, under Dashboard > IPsec Monitor, I see the connection.  But no traffic passes over the tunnel and Received Bytes stays at 0.

Interestingly enough, using the exact same Windows 11 laptop, I'm able to connect to the same VPN connection on one network (source IP) and transmit data, but on other networks I've tried (including hotspot'd to my phone's WiFi connection), I can connect to VPN, but no data passes.  These other networks were networks where the connection previously passed data no problem over the VPN.

I've tried the following:

•Uninstalling and reinstalling the Forticlient VPN 7.4.1 software

•Uninstalling 7.4.1 and installing 7.4.2

•Disabling IPv6 on the tunnel adapter

•Disabling IPv6 on all other adapters

•Installing the latest January Windows 11 updates

So far, nothing has solved the issue.

[funkylicious]

try installing, https://learn.microsoft.com/en-us/cpp/windows/latest-supported-vc-redist?view=msvc-170

see if you have windows update KB5026372 installed and uninstall it ( this was recommended for SSLVPN but you can try for IPsec )

also, have a look at https://community.fortinet.com/t5/FortiGate/Technical-Tip-No-bytes-are-received-when-connected-to-IP... 

[link470]

> try installing, https://learn.microsoft.com/en-us/cpp/windows/latest-supported-vc-redist?view=msvc-170

I forgot to mention that I'd ensured Visual C++ 2015-2022 was installed as part of installing FortiClient VPN (it was), and I did attempt to update it just in case to the latest version from Microsoft.  This didn't fix the issue.

> see if you have windows update KB5026372 installed and uninstall it

That Windows Update wasn't installed on this machine; that particular update is for Windows 11 v22H2 and I'm running v24H2.

> also, have a look at https://community.fortinet.com/t5/FortiGate/Technical-Tip-No-bytes-are-received-when-connected-to-IP... 

This only applies to IKEv1 connections by the looks of it.  I'm using IKEv2.

Good news though, fixed!  See my reply to MZBZ.

[MZBZ]

1. make sure NAT is NOT disabled on the FortiGate side. should be enable or forced.

2. check this article: https://community.fortinet.com/t5/FortiClient/Troubleshooting-Tip-IKEv2-IPSec-VPN-on-FortiClient-v7-...

[link470]

This did it, thank you!  Setting Encapsulation to Auto (UDP fallback TCP) was the necessary configuration.

[michael2406]

Hello @link470 , did you now establish the connection via tcp or udp? With udp it seems to work, but not with tcp for me. 

What is your FortiClient setting? Also auto or tcp?