Answer A is incorrect because you cannot make Windows 2000 Professional
machines demand dial routers. Windows 2000 Professional does not include the
Routing and Remote Access service and therefore you cannot create demand-dial
routing connections between the sites with this solution. In addition, NAT
(Network Address Translation) does not allow you to configure demand-dial links
and is not involved with the creation of demand-dial routing or VPN demand-dial
links. NAT is one of the routing protocols included in the Windows 2000 Routing
and Remote Access service.
Answer B is incorrect because you run into the cost-prohibitive solution of using dedicated point-to-point links between the sites. If the company were to
maintain continuous point-to-point links via two ISDN modems, they would have to
pay long distance charges for the time online, as well as possible packet
charges depending on the policies of the local telephone company. This is also a
somewhat unusual setup in that a dedicated point-to-point connection is used to
tunnel data between the sites. This can be done to add more security, however.
Another problem is that the connection is a one-way connection, which would
leave the other users unable to access resources on the opposite subnet.
Answer C is correct because you can save money by creating a demand-dial
point-to-point routed connection between the sites. The link will stay active only as long as
it is needed, and then the line will be dropped.
Answer D is correct because you can save money by using dedicated connections
to local ISPs, and then create demand-dial VPN connections to route packets
between VPN gateways. The link will remain active only as long as it is needed,
and then the tunnel is torn down. This adds security to the VPN solution.