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No Network Connectivity on TCP/IP-Based Network

This article was previously published under Q185753
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You may not be able to view or connect to any shared resources on anetwork that uses the Transport Control Protocol/Internet Protocol(TCP/IP), even though your network adapter and network server settingshave been verified to work correctly.
This problem can occur if you change the Internet Protocol (IP) addressfor your computer to any of the following invalid IP addresses in theTCP/IP Properties dialog box:
  • 127.<x>.<y>.<z>
To specify any of these addresses, you must click Specify An IP Addresson the IP Address tab in the TCP/IP Properties dialog box, type theinvalid TCP/IP address, click OK, click OK when you receive the followingmessage, and then click Cancel:
The specified IP address is not valid. Please check that the value you typed is correct. If you believe the value is correct but you still receive this message, check with your network administrator.
To work around this problem, change the IP address to a valid IP address.To do so, follow these steps:
  1. Click Start, point to Settings, click Control Panel, and then double- click Network.
  2. On the Configuration tab, double-click either TCP/IP or "TCP/IP-><network adapter>," where <network adapter> is the name of your network adapter.
  3. On the IP Address tab, type a valid IP address in the IP Address box, and then click OK. If you do not know a valid IP address for your computer, contact your network administrator.
  4. Click OK, and then click OK.
Microsoft has confirmed this to be a problem in Microsoft Windows 95, Windows 98 and Windows Me.
Networks that use TCP/IP set a unique IP address for each computer todetermine its identity. The IP address is reserved for testingthe TCP/IP stack with the PING command. The following table lists IPaddresses that are not valid for a computer, where <x.y.z> is a range ofnumbers from 0 to 254.

   Invalid IP address   Valid (reserved) usage   -----------------------------------------------------            Loopback/LocalHost address            Class A subnet mask          Class B subnet mask        Class C subnet mask   225.<x.y.z> -        Class D address (multicast only)				
240.<x.y.z> - Class E address (reserved)
254.<x.y.z> Broadcast address

If you use any of the addresses listed above as the IP address for acomputer, no other computer can successfully communicate with it.

A subnet mask is an address for a subnetwork used to expand the range ofpossible IP addresses on the network. A subnet mask acts to identify anIP address on different subnetworks. TCP/IP uses the binary format toresolve an IP address and subnet mask.

Both the IP address and the subnet mask use binary format for each octet.An IP address consists of four octets. The portion of the octet in binaryformat that is not used by the subnet mask becomes the portion of the IPaddress that differentiates it from other IP addresses on the samesubnetwork. The assigned IP address and the subnet mask are combined inbinary format to create the resolved IP address in a TCP/IP network. Ifthe resolved IP address in binary format is all zeros or ones (forexample, 11111111, or decimal 255), it is an invalid IP address.

The following table lists sample IP addresses and subnet masks for an IPaddress on a Class C subnetwork. These addresses assume that the firstthree octets of each IP address and subnet mask are valid.
   IP address     Subnet mask      Resolved IP address   Result   -------------------------------------------------------------   00000001 (1)   11111100 (252)   11111101 (253)        valid   00000011 (3)   11111100 (252)   11111111 (255)        invalid				

For information about troubleshooting TCP/IP, please see the followingarticle in the Microsoft Knowledge Base:
ARTICLE-ID: 172218
TITLE : Microsoft TCP/IP Host Name Resolution Order
HWNICCON connect nic

Article ID: 185753 - Last Review: 01/23/2007 15:53:11 - Revision: 2.1

  • Microsoft Windows Millennium Edition
  • Microsoft Windows 95
  • Microsoft Windows 98 Standard Edition
  • kbenv kbnetwork kbprb KB185753