Re: Win95 won't forget old IP address

[Ken Key <[e-mail]>]

I believe you will find that the DHCPNAK is being sent to the unicast address
or the (sub)net-broadcast address rather than the all-ones broadcast address.
In my testing with the MS DHCP clients, I noticed they ignore any NAK
that wasn't sent to the all-one's B'cast address.  This is problematic with
Net2-based networking kernels as they turn any all-ones >B'cast into a 
(sub)net-broadcast just before they hand them off.  But since it works on
the local net but not through the router, my guess is that your router
isn't noticing the B'cast bit on the NAK being set (assuming that ISC's
server sets it) and is thus sending a Unicast response to the Win95 box
just like it would for any BOOTP response.  I've run into this with the 
ancient version 9.x router I currently have on my test-net.

regards,
Ken Key
PS.  I'm not with *that* part of cisco, so I don't know if later/current
versions deal with the B'cast bit.


> 
> > 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.
> > 
> > And that's it.  The Win95 client doesn't then request a new address on its
> > new subnet or anything.  So I tried to make the Win95 machine forget about
> > its old address.
> 
> What's happening here is that the client is in the RENEWING state, not
> the REBINDING state, so if its DHCPREQUEST doesn't get a response, it
> blissfully keeps using the old address until it gets to the REBINDING
> state, at which point it will eventually broadcast a DHCPDISCOVER and
> probably be dealt with correctly.
> 
> The next question is, why isn't it getting the DHCPNAK?  I'm not sure
> - I don't have enough information.  Is this client connected to a
> network to which the DHCP server is also connected?  Can you send me a
> complete log of what the server prints out when you start it and when
> you move the client from one net to the other?  (The dhcp-v4 list
> probably doesn't need to see this.)
> 
> 			       _MelloN_
--
Ken Key    ([e-mail])  | cisco Systems, Inc.   | (Formerly TGV, Inc.)  
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