Automatically Reset DHCP Leases for Win95/WinNT/WFWG Clients

• Microsoft Windows NT Server versions 3.5, 3.51, and 4.0
• Microsoft Windows NT Workstation versions 3.5, 3.51, and 4.0
• Microsoft Windows 95
• Microsoft Windows for Workgroups version 3.11

SYMPTOMS

If a scope is removed in DHCP Manager and another scope is defined, Microsoft-based DHCP clients will not automatically renew their lease to conform to the new scope.

CAUSE

The DHCP clients will not renew their leases automatically until half of the lease time has expired. Microsoft DHCP Server cannot force clients to renew their leases when the DHCP scope has changed.

RESOLUTION

There are two ways the DHCP client computers will renew their leases automatically:

• Wait until half of the allotted lease time expires. The clients will then renew their leases automatically.
• Force a DHCP client to renew its lease by doing one of the following:

      - On a Windows NT Workstation or Server or a Windows for Workgroups
        3.11 DHCP client, use the Ipconfig.exe utility with the /RENEW option
        at a command prompt:
  

           ipconfig /renew
  
        -or-
  
      - On a Windows 95 DHCP client, use the Winipcfg.exe utility. On the
        Start menu, choose Run and type the following and click OK:
  
           winipcfg
  
        In the dialog box, select the RENEW option.
  
  

However, with the introduction of Windows 95, the command-line option is no longer available. Use the Ipconfig.exe utility from Windows for Workgroups 3.11. This utility works correctly with Windows 95 computers and the IPCONFIG /RENEW option can once again be used for these computers.

The following is an example of a Windows NT login script for automatically renewing DHCP clients, assuming Ipconfig.exe from Windows for Workgroups 3.11 is on \\Server\Win95. For this example, drive letter Y was used. Any available drive letter can be used for this purpose.

  NET USE Y: \\SERVER\WIN95
  IF EXIST C:\WINDOWS\IPCONFIG.EXE IPCONFIG.EXE /RENEW ;WFW
  IF EXIST C:\WINNT35\SYSTEM32\IPCONFIG.EXE IPCONFIG.EXE /RENEW ;WINNT
  IF EXIST C:\WINDOWS\WINIPCFG.EXE Y:\IPCONFIG.EXE /RENEW ;WIN95
  NET USE  Y: /d ; Deleting the drive letter mapping