In the process of evaluating ISA as a firewall I noticed that my L2TP tunnel that was working between the two test servers suddenly stopped working, I am beginning to think that a certificate server is required to maintain this tunnel. I did however make one modification in RRAS, I set the connection state to persistent on both ends. Could anyone tell me if a Cert server is absolutely necessary for tunnels to work when created between two or more ISA servers. Thank you Glenn