Here is the problem :
Router A with fixed IP, Router B with dynamic IP
So, according to what I read, only router B can initiate the VPN connection.
When I try to reach Router A from Router B, the VPN goes up instantly and everything works perfectly.
The problem is that I only need the VPN connection from A to B, and when A needs to communicate, the VPN is down for time out reason and the VPN can be initiated this way.
I though that entering "crypto isakmp keepalive 20 periodic" on Router B will solve the problem but no.
Can you help me please ?