Configuring DRAS with Reserved IP Addresses for Private Networks

Per RFC 1597: Section 3: Private Address Space, The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private networks: 10.0.0.0 - 10.255.255.255 , 172.16.0.0 - 172.31.255.255, and 192.168.0.0 - 192.168.255.254.

These network IDs and the associated IP addresses may be used freely in any internal network scheme and will not affect interoperability with the Internet as a whole. In particular, the class C range is the preferred range to use when configuring the async connectors of Microsoft Exchange Server.

Each async interface on a Windows NT Server computer requires two (2) ip address; one for the server and one for the client of the particular session. The network ID of the async interface should be such that the async interface is on a different subnet than the network interface of the server; as such the unit is multihomed. Using a subnet mask of 255 in the third octet of the class C address allows 255 networks with 254 hosts on each network; this facilitates ease of planning and configuration.

For example, connect 3 Exchange sites through the Dynamic Remote Access Service (RAS) connector. Each Exchange Server computer has a single modem.

1. In the RAS configuration, select a static pool of addresses.
2. Configure the pools on each server as follows.
   

         Server_1 192.168.1.1 and 198.168.1.2;
         Server_2 192.168.2.1 and 192.168.2.2
         Server_3 192.168.3.1 and 192.168.3.2.

Thus the RAS server session on each server will get the .1 address and the client session will be assigned the .2 address.