This is a very strange problem and would appreciate any gurus out there to help, if possible. We have a server and a VPS, say A and B. Server A has csf installed and VPS B has no firewall at all. When we try to PING as root on EITHER server, NONE of them can ping each other but they BOTH work fine if we PING other servers which we have. Apparently, either A or B is blocking each other and since only server A has csf, we added the VPS B to its allowed lists but its still not working. Any ideas?