DHCP discovery of WINS servers

Shirish Kalele kalele at veritas.com
Tue Sep 4 09:48:08 GMT 2001

On Tue, 4 Sep 2001, Christopher R. Hertel wrote:

>Hi Shirish!  Missed you at the conference.
Thanks, Chris. Air travel in the US is something I avoid at all costs :-)
and besides, maybe I'm lost, but I don't really see the point of
continuing to have CIFS conferences when Microsoft is obviously not going
to make CIFS open seeing as it doesn't have anything to gain.
Interoperability testing is probably the only reason. And for Samba, a
simple download is all it takes to do that.

>Regarding the use of DHCP to grab WINS info...
>Can't we form a DHCP request that asks for only the netbios-name-servers
>field?  We would need to do the dhcp discover to find the dhcp server.
Yes, we do do a DHCPinform request asking only for the nbns list. This is
a newer request, and older DHCP servers drop it. If DHCPinform fails, we
fall back to doing a DHCPdiscover again requesting the nbns list. In response to the
discover request, we get a DHCPoffer offering us an IP address and the
other config info we requested (in our case, the nbns list). We grab the
list of wins servers and drop the offer.

>This is where Windows integration of NBT into the kernel is an advantage. 
>They can (and probably do, but I haven't checked) include the request for 
>the netbios-name-serevers in the initial DHCP exchange.
There might be a way to include such a request even for Unix systems. I
haven't really played with dhcp configuration on Unix.

>Question: If we do a DHCPdiscover and request the netbios-name-servers
>option, will that mess up the system's IP address lease?  I don't think so
>(shouldn't) but it's worth checking.  Also, is it possible to query the 
>lease time for a system so we know when the host system will be doing a 
>"real" DHCP update?
I don't think so, because nmbd would get the offer, not the system. And
we don't negotiate any further after we have a DHCPoffer, so we are never
assigned a new IP lease.

- Shirish

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