How to avoid problems arising from APIPA

Posted On 2007-02-13 by FortyPoundHead
Keywords: APIPA
Tags: Networking Tip Windows XP
Views: 1716

Windows XP computers can be assigned IP addresses two ways: manually using static addresses or automatically using DHCP.

If your computer is configured to use DHCP however, a problem can occur if the DHCP server is down when your computer needs to renew its lease. This happens typically if you reboot your computer when the DHCP is unavailable, and in this case Windows XP uses Automatic IP Address Allocation (APIPA) to automatically assign itself an address of the form 169.254.x.y.

Once your computer has this address however, it typically can''t communicate on the network anymore. To prevent this kind of situation from happening, you can assign your computer an alternate IP address to fall back on when your computer can''t contact a DHCP server to lease an address. This is done by using the Alternate Configuration tab of the TCP/IP properties for your computer''s Local Area Connection.

A typical situation where you might want to use this might be if you have a laptop at home where you use DHCP to obtain an IP address from your ISP. If you take your laptop to work sometimes and your workplace is a small business that uses static addressing instead of DHCP, you can assign your computer a static address on the Alternate Configuration tab so that it can participate in your work network when present at work.

Note that the Alternate Configuration tab is only visible when you''ve selected Obtain An IP Address Automatically on the General tab of your TCP/IP Properties.

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