I have a Cisco ASA 5520 firewall device, we have configured about 60 site-to-site vpn tunnels to our clients. In the recent days at least once in a day all my VPN tunnels flaps, all I will do is "clear crypto isakmp sa" & then the VPN tunnel works fine, this has become now a regular practice, All I wanted to know the root cause for this that why this is happening only on a particular time.
I have 2 Cisco ASA with the same hardware & s/w other acting as a standby device.
Cisco Adaptive Security Appliance Software Version 8.0(2)
Device Manager Version 6.0(2)
Compiled on Fri 15-Jun-07 19:29 by builders
System image file is "disk0:/asa802-k8.bin"
Config file at boot was "startup-config"
Hardware: ASA5520, 512 MB RAM, CPU Pentium 4 Celeron 2000 MHz
Internal ATA Compact Flash, 256MB
BIOS Flash AT49LW080 @ 0xffe00000, 1024KB