Good day!
I have l2tp+ipsec server on my ccr1036-12g-4s RouterOS 6.20. Less than a month ago began appearing error about ipsec (screenshot in
attached file). Appears whether someone is connected or not connected.
Can you help me understand what’s wrong?
Hi,
this is pretty little information you provide 
As a first shot I’ll recommend to take a look at yoour proposal which obviously doesn’t match the peer’s expectations.
Have a look at the PFS group property. It’s “none” by default, try setting it to “modp 1024”.
Also carefully look at the Auth and Encryption algorithms.
For more detailed debugging, add the ipsec topic to your logging rules.
If the remote peer is a Cisco device, you’ll pretty quickly find the reasons in their (debugging) logs.
Cheers
-Chris
Hi.
PFS group is set to “modp 1024”. Authorized users do not have any problems with connecting, and this error occurs when no one is to use a VPN connection and no one try to connect.
Maybe someone else trying to connect?