Forgive me if this has been discussed before.
I have an L2L between an ASA5520 and 871 on static IPs. For some reason, I cannot get the tunnel to form from the ASA side - but can trigger tunnel formation by issuing pings from the 871 - using VLAN1's IP address as the source. One the tunnel forms, pings from behind the ASA keep the tunnel alive - but once they are stopped - the tunnel drops and will not re-form. All of my other L2L to not exhibit this problem.
Any ideas? Am I missing some keepalive parameter on one of both ends of the L2L?