Windows 98 TCP/IP AutoConfiguration

by Johannes Helmig [Published on 15 July 1998 / Last Updated on 15 July 1998]

If a new network-board is installed and configured, Windows98 installs as default protocol TCP/IP, configured to automatically obtain an IP-address:

If you do NOT specify yourself the IP-address or you have a DHCP-server on your network, Windows98 will take longer (a lot longer) to boot, but it did assign an IP-address to the network-card, as can be verified with "winipcfg":

The article Q188480 in the Microsoft Knowledge Base (, which also points to the file "\tools\mtsutil\mtsutils.txt" on your Windows98 CD-ROM), has the following explanation:


The Windows 98 TCP/IP stack supports a new mechanism for automatic
address assignment of IP addresses for simple LAN-based network
configurations. IP Autoconfiguration Addressing is an extension of
dynamic IP address assignment for LAN adapters. It enables
configuration of IP addresses without using static IP address
assignment or installing a Dynamic Host Configuration Protocol
DHCP) server.

If a network LAN adapter is configured for TCP/IP, and if "Obtain
an IP address automatically" is selected on the IP Address tab in
the TCP/IP Properties dialog box, Windows 98 TCP/IP attempts to find
and use a DHCP service on the attached network to obtain a
dynamically assigned IP address. If it does not find a DHCP service,
Windows 98 uses IP Autoconfiguration Addressing by assigning the
adapter an Class B IP address out of the network number 169.254.x.x
IP address space. In this way, two PCs can be plugged into a LAN hub
and can start without any IP address configuration, and can use
TCP/IP networking for internetworking. Each computer that uses IP
Autoconfiguration Addressing gets an IP address and tests to
determine that the IP address is unique and not already in use on the

IP Autoconfiguration Addressing is enabled by default. IP
Autoconfiguration Addressing can be controlled by setting the value
of IPAutoconfigurationEnabled (type DWORD) in the registry key


If the value of IPAutoconfigurationEnabled is nonzero or if the
registry key is absent, IP Autoconfiguration Addressing is enabled.
An IPAutoconfigurationEnabled value of 0 disables the IP
Autoconfiguration Addressing feature.

If Windows 98 initially does not detect a DHCP service and configures
an IP Autoconfiguration IP address, and then it subsequently
discovers a DHCP service on the network, Windows 98 uses the DHCP
service and switches from 169.254.x.x addressing to IP addresses
assigned by a DHCP server.

I do not know (or did find anywhere info) on how Windows98 assigns the TCP/IP-address.
I verified also the procedures listed in the article Q188480 and the file "mtsutils.txt" on switching off/on this IP-AutoConfiguration, the required install-files "ipac_off.inf" and "ipac_on.inf" are also on the Windows98 CD-ROM:

I had a look in the registry and located the key:

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