The Problem: After a period of time during a VPN session the Z110G would reboot. At first this was usually about 10 minutes, but it could be cumulative as some sessions caused a reboot in considerably under 10 minutes. The Z110G would get a new IP address (usually) and you could not reconnect until the DDNS system got the new IP address (the Z110G did get the same one back once).

The initial tests were done using a laptop running Windows XP. This software had various non-standard software including a Cisco VPN client and a Sprint Dialup client.

If you can get the IP address it will reconnect reliably but reboot at some point. (I was using a cell connection device with a laptop to test from home.)

It does not seem to be a configuration problem with the Z110G.

Connected from two different links - a cell device and a T1. No difference. This rules out the cell connection device and software.

A lack of traffic is not the reason for the reboot. Continuous pings were going during some of the reboots.

Z100G Tech Support said it is not a problem with the router and they did stay connected for 90 minutes. (Thanks!!!)

Left Z110G running for almost two weeks. No spontaneous reboots. A VPN session is the one thing that is definitely associated with the reboot.

Waited for new firmware - 7.0.38x. Tried again.

On a T1 I used a newly rebuilt laptop computer (Windows XP Pro) on a Windows 2003 domain with standard software and with the Sprint dial-up client and Cisco VPN client installed but never used. Stayed connected for 45 minutes - a record. Z100G rebooted and killed the connection. A continuous "ping" was running as was an admin session with the Z110G when it rebooted. I had done a Remote Desktop session to an inside computer but that was not active when it rebooted. The admin session with the Z110G was probably not the source of the problem since it had not been active upon reboots during previous tests. This computer did not have some of the utilities of the other laptop so those utilities are probably not implicated at this point. Did do some config changes to the Z110G. These normally do not cause a reboot.

On a T1 I used a brand new desktop computer on a domain with all standard software (no Cisco VPN or Sprint Dial-up software). Did not do any Remote Desktop sessions or access the Z100G. The only traffic is a continuous "ping". Did this for one hour without any problems. Then accessed Z100G admin. Seemed to go OK. Tried a remote desktop connection with the Vista computer more than once. Did several things including a Microsoft update and copying a file to the remote computer. VPN ran for 2 hours without any problems. That rules out the computer being on the Domain.

The most likely suspect is the Cisco VPN client software which does have a background component that runs on bootup.

Difficulties encountered during troubleshooting:
- The Z100G does not seem to be updating the DDNS system with the new IP address after a reboot so you have to wait until it does before VPN works again (or somehow get the IP address and make a new "Site"). This update period seems to be overnight or at least a substantial period of time. This has made troubleshooting very time consuming. Do one thing that fails and you have to wait until the next day to try again.

- Log file is wiped during reboot so I could not tell what happened. Sending data to a syslog server might have helped.