In article , Al wrote: :I have a problem with connecting multiple Cisco VPN clients that are :behind a firewall to a VPn concentrator. At the moment only 1 person :can connect.
That's a standard problem. Turn on NAT Traversal (the link shows how), and make sure that UDP 500 and UDP 4500 are open.
Without NAT-Traversal being on, ESP (IP Protocol 50) is used, and since ESP has no 'port', very few firewalls are able to NAT more than one internal ESP source to a shared IP address. NAT-T encapsulates ESP within UDP and so works fine with PAT (Port Address Translation.)