how to change isc-dhcp3-server replies? (was: isc-dhcp3-server
issues with windows 2000 client)
fbsd.questions at rachie.is-a-geek.net
Sat Sep 1 14:52:19 PDT 2007
On Saturday 01 September 2007 23:30:27 Peter Boosten wrote:
> Joe wrote:
> > Hello, after running tcpdump for a while I discoverd what is going on
> > with my dhcpd server and why some clients are not able to get an IP
> > address from it, in particular windows clients. It turns out it is not
> > just win2k but any windows.
> > It seems that the dhcpd server is replying to the subnet and not the
> > broadcast net. So the reply that should be sent to 255.255.255.255:68 is
> > sent to 192.168.0.255:68. Then, because the client has no IP address or
> > has defaulted it to a 169.x.x.x(MS defaults) it does not seem to be
> > getting the reply and thus never gets an address assigned.
> I have no problems running dhcp3 with windows clients at all... As far
> as I can tell the broadcast address of a subnet *never* is 255.255.255.255.
It is for DHCPDISCOVER, since there is no subnet yet:
# dhclient -d fxp0
DHCPDISCOVER on fxp0 to 255.255.255.255 port 67 interval 4
As for the option you're looking for, man dhcpd.conf showed me this:
The DHCP and BOOTP protocols both require DHCP and BOOTP clients to
set the broadcast bit in the flags field of the BOOTP message header.
Unfortunately, some DHCP and BOOTP clients do not do this, and there-
fore may not receive responses from the DHCP server. The DHCP
server can be made to always broadcast its responses to clients by
setting this flag to 'on' for the relevant scope; relevant scopes
would be inside a conditional statement, as a parameter for a class,
or as a parameter for a host declaration. To avoid creating excess
broadcast traffic on your network, we recommend that you restrict the
use of this option to as few clients as possible. For example, the
Microsoft DHCP client is known not to have this problem, as are the
OpenTransport and ISC DHCP clients.
Worth a shot :)
People using reply to all on lists, must think I need 2 copies.
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