I am running a site to site VPN between a Cisco PIX 501 & PIX 506. Both filewalls are then connected via an Cisco 837 router to the Internet. This has been extremely reliable and I have had no problems accessing the private networks so far. Recently I decided to connect an Nortel IP phone to a Nortel BCM between the two sites. The IP phone connects to a Nortel BCM across the VPN and I am able to make and take calls but for one problem. When a call reaches around 4 minutes or so the IP phone disconnects from the server then reconnects. When the phone is idle it remains connected to the BCM without any problems. This consistently happens and I have done the usual things like trying a different phone etc to no avail. I have tried the IP phone on the LAN local to the BCM and it works fine with no dropouts so it appears to be an issue across the VPN? I have tried a different VPN connection across a different link and the same thing happens. Both PIXs are running the latest OS Help!