We are using cyberoam device, VPN IPSEC tunnel is going of frequently even the traffic is throug.
Please suggest what may be the cause for the above mentioned issue.
Also suggest a best tool to monitor the same VPN IPSEC tunnel connectivity.
You mean the VPN is disconnecting even though connectivity seems fine?
Yes Exactly the same DGPickett.....
Anything in the logs? Run a continuous ping from site A to site B. Does it drop periodically and then restart? Usually when an IPSEC tunnel drops, you'll see the handshake details if you have logging or debugging enabled. If the problem goes AWAY while running a continuous ping, then it may just be timing out for inactivity. As far as monitoring goes, consider Nagios to monitor the connection for drops. As an aside - I like a windows app called "ServersAlive" for simple monitoring of services/links/uptime... not terribly expensive, and great red light/green light online status that the helpdesk staff appreciates.
Maybe you can option it for more retries, longer wait so the IPSEC tunnel is more robust?