I have IPsec Site-to-Site VPN from my ASA to customer. After customer complain about VPN down, I reset the tunnel now I can see Login time duration 12h:34m Byte TX is 543240 and Byte Rx is 0. What might be the issue. How can I troubleshoot further ?
Based on your inputs, it appears that the issue is on the remote end unless you didn't make any changes on your earlier working setup.
As the packet encaps are happening at your side and no decaps on the remote side, these are the below things to consider.
- Check whether you have routes to reach the remote subnet/IP over the internet.
- Check for the NAT statement on your firewall whether the interesting traffic is properly interpreted.
- Enable the packet captures for the remote subnet/ IP and check for the packet logs
Request the remote customer network/VPN team to check the same things at their side. This will give a clear picture to troubleshoot the things.