A: To make IPSec work through your firewalls, you should open UDP port 500 and
permit IP protocol numbers 50 and 51 on both inbound and outbound firewall
filters. UDP Port 500 should be opened to allow Internet Security Association
and Key Management Protocol (ISAKMP) traffic to be forwarded through your
firewalls. IP protocol ID 50 should be set to allow IPSec Encapsulating
Security Protocol (ESP) traffic to be forwarded. Finally, IP protocol ID 51
should be set to allow Authentication Header (AH) traffic to be forwarded.