Re: Win95 won't forget old IP address

[Mark Sirota <[e-mail]>]

Michael J. Lewis wrote:
> Mark Sirota wrote:
>>
>> I've got a Windows 95/Plus client which is booting via DHCP.  If I move
>> the machine to another subnet, it requests (via DHCPREQUEST) the IP address
>> it had before.
>>
>> The daemon refuses (DHCPNAK), since the request is coming from a different
>> subnet.  The client REQUESTs again immediately, and again the server NAKs.
> 
> What server are you using?  In the tests we've done, Windows 95 will respond
> with a DISCOVER to a NAK.  The only time the dual REQUEST then continue with
> the same address scenario occurs is if there is no response to the REQUESTs
> or an invalid response is received.

Aha!  So the Win95 machine is not receiving the NAK, or is not recognizing
it.  More research is indicated.

I am using the ISC DHCP Server, Beta Release 4 Patchlevel 4.  I have copied
the ISC DHCPD mailing list in on this message, since perhaps someone there
can help.

The server and client are on opposite sides of a router -- in this case, a
Cisco with a helper address configured to pass the DHCP request along to the
server.

Interestingly, if I take the machine back to the same subnet as the server,
it sees and understands the NAK, and responds with a DISCOVER, just as you
say it should.

Therefore, apparently being on the other side of the Cisco causes some
breakdown in the transmission, receipt, or recognition of the NAK.  Anyone
have any thoughts on that before I break out the sniffer?

> You should be able to run WINIPCFG and RELEASE the address.

Many thanks to everyone who told me about this.  It seems like everyone in
the world knew about this except me...  Sigh.

-- 
Mark Sirota, Network Systems Engineer
University of Pennsylvania, Information Systems and Computing
[e-mail], 215/573-7214