I have a ASA 5520 that has several PIX 501 and Cisco 871's which connect to it using a EZVPN connection. For some strange reason only 2 or 3 of the connections will drop on the ASA 5520. The 871 on the other end still shows a VPN tunnel as being up even though the ASA shows it as not connected. Traffic will not cross when it is in this state. It is always the same 871's with the issue. The tunnel will recreate on it's own from time to time but at not set time. It may be in 15 minutes or 5-6 hours.
If the 871 is power cycled they will come right back up and work for 30 minutes up to 16-18 hours before it happens again.
I have monitoring software behind the ASA 5520 that connects to the 871's inside interface once per minute to verify that it is up. Therefore, there is traffic crossing that link at least once every 60 seconds. The packets are small but there is always data traveling.
I have swapped out 871's at these remote locations, but the issue still appears. Also the internet providers are different at each of these locations. All providers that I talked to state that they see no issues with our connection to the internet.
Any help would be great.