ICS Does Not Route IP Packets with Class-Mismatched Static IP Address and Subnet Mask

If you turn off the Dynamic Host Configuration Protocol (DHCP) service on an Internet Connection Sharing (ICS) host and instead manually assign static IP addresses with a different class of subnet mask on the local area network (LAN), you may experience the following issues:

• On the ICS client computer, Microsoft Internet Explorer may display a "This page cannot be displayed" message.
• You may be able to ping the ICS host from the client ICS computer, but you may not be able to ping any known good Internet host using the IP address or friendly name.

This behavior can occur if the home network's static IP address and subnet mask belong to a different class of TCP/IP address and subnet mask. For example, this behavior can occur if you are using a class A network address (for example, 10.0.1.x) with a class C subnet mask (for example, 255.255.255.0) on the LAN.

In this situation, Network Address Translation (NAT) does not work correctly and the IP routing on the ICS host does not function.

To resolve this issue, use the same class of IP address and subnet mask on the LAN.

For example, use a class C network address (such as 192.168.0), with a class C subnet mask (such as 255.255.255.0).

Although you can change the TCP/IP settings in ICS, Microsoft Product Support Services does not support customizing your TCP/IP settings. Microsoft Product Support Services does support the default configuration for ICS.

For additional information about configuring static IP addresses on an ICS network, click the article number below to view the article in the Microsoft Knowledge Base: