DOCUMENT:Q139983 08-AUG-2001 [winnt] TITLE :Class C Subnetting Options for RAS Routing PRODUCT :Microsoft Windows NT PROD/VER:winnt:3.5,3.51,4.0 OPER/SYS: KEYWORDS:kbnetwork ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0 - Microsoft Windows NT Server versions 3.5, 3.51, 4.0 ------------------------------------------------------------------------------- SUMMARY ======= Windows NT Remote Access Service (RAS) routing for LAN connectivity to an Internet Provider requires an IP subnet address for the local LAN and a different subnet addresses for the RAS link. This article describes subnetting options with a class C address. A class "C" address must be registered with the InterNIC. The InterNIC can be found at http://rs.internic.net or by sending mail to Hostmaster@NIC.DDN.MIL . Your Internet Service Provider may also supply you with a valid range of addresses. MORE INFORMATION ================ Following are 3 options to configure different subnet addresses for the RAS link and local LAN: Option 1 -------- Have the Internet Provider give you one address to use on your RAS link outside of your class C addresses. This leaves you with the full 254 addresses for your own use and no special subnetting. Many Internet Providers will not give you an additional IP address. They may give you an entire additional class C range for a fee. Option 2 -------- Subnet mask of 255.255.255.192 This gives you 2 valid subnets with a maximum of 62 clients on the local LAN. Subnet 1 would have the fourth octet of 64-127 (65-126 can be assigned). Subnet 2 would have the fourth octet of 128-191 (129-190 can be assigned). For example XXX.XXX.XXX.65 would be the first address of subnet 1 and could be used for the Windows NT network card and XXX.XXX.XXX.129 would be the first address of subnet 2 and could be used for the RAS connection. Option 3 (unsupported) ---------------------- Subnet mask of 255.255.255.128. This gives you 2 subnets with a maximum of 126 clients on the Local LAN. Both subnets are technically invalid but work with Windows NT 3.5 and 3.51. Be sure all clients on the network support this subnet mask. Microsoft cannot guarantee this will work in future releases of Windows NT. Subnet 1 would have the fourth octet of 0-127 (1-126 can be assigned). Subnet 2 would have the fourth octet of 128-255 (129-254 can be assigned). For example XXX.XXX.XXX.1 is the first address of subnet 1 and could be used for the Windows NT network card and XXX.XXX.XXX.129 is the first address of subnet 2 and could be used for the RAS connection. Additional query words: prodnt ====================================================================== Keywords : kbnetwork Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT351search kbWinNT350search kbWinNT400search kbWinNTW350 kbWinNTW350search kbWinNTW351search kbWinNTW351 kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWinNTS351 kbWinNTS350 kbWinNTS351search kbWinNTS350search Version : winnt:3.5,3.51,4.0 Issue type : kbhowto ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.