Microsoft Knowledge Base Article 313195 contains the following summary:
Windows 2000 supports the use of Internet Protocol security (IPSec)
to secure communications between computers. IPSec is a cross-platform protocol. Windows 2000-based computers
use IPSec policies to control which communications require the use of IPSec. A computer can require that IPSec secures
all communications, or only a subset of all communications can be required to use IPSec. You use IPSec filters to control when IPSec
To test the IPSec policies, use IPSec Monitor. IPSec Monitor (Ipsecmon.exe) provides information about which IPSec policy is active and whether a secure channel between computers is established.