I have 4 ASA 5505's with Site-to-Site IPSEC VPN tunnels built between them. One of the tunnels stays up just fine but the other 2 drop at the end of the SA lifetime for a period of time equal to 10% of the SA lifetime.
Orignially, I had the the lifetime set to 1 hour and the tunnels would drop for 6 minutes. I changed the lifetime to 8 hours (480 minutes) and they dropped for 48 minutes. I've gone over the configurations and the only differences I can find is that the sites where the tunnel drops have the outside interface forwarded to an VOIP server and all ports but SIP blocked.
