Q. I have read that some ISPs block VPN. Is this likely to be a problem?

A. No. ISPs that block VPNs typically block the IP protocols ESP (50) and AH (51). The Cisco VPN implementation uses UDP, not ESH or AH to establish the VPN tunnel. In the course of a lengthy and extensive VPN Pilot Project, no problems with ISP-blocked VPNs were encountered.