Glenn Satchell glenn.satchell at uniq.com.au
Fri Mar 19 10:59:43 UTC 2010

Make sure you spell it correctly in the conf file. Due to the way the 
parser works a spelling mistake on a single keyword can be parsed as a 
variable :) This is not in the documentation, but if you search the mail 
archives you will find this mentioned...

So, in this example there are no relays, only directly connected 
clients? Check the always-broadcast on; statement in the dhcpd.conf man 
page. It may (or may not) help.

What is shown in the logs of the dhcpd server?

Try using a packet sniffer (eg ethereal, snoop, tcpdump) to look at the 
traffic to see what flags and settings are in the actual request packets.


On 03/19/10 21:46, kalyan Alle wrote:
> Ya i have kept authoritative; at the top of the conf file. Still iam
> facing the same issue.
> Plz let mw know if i have to do something else .
> -kalyan
> On Fri, Mar 19, 2010 at 3:46 PM, kalyan Alle <kalyan.alle at gmail.com
> <mailto:kalyan.alle at gmail.com>> wrote:
>     I did not try it.
>     I will try  putting authoritative at the beginning of the conf file.
>     thanks glenn.....
>     On Fri, Mar 19, 2010 at 3:40 PM, Glenn Satchell
>     <glenn.satchell at uniq.com.au <mailto:glenn.satchell at uniq.com.au>> wrote:
>         Have you included the  authoritative  statement? by default ISC
>         dhcpd is not authoritative. See dhcpd.conf man page, following
>         on from the earlier section already posted:
>              ...
>                          If the server knows nothing about  the  address,
>              it  will  remain silent, unless the address is incorrect for
>              the network segment to which the client  has  been  attached
>              and the server is authoritative for that network segment, in
>              which case the server will send a  DHCPNAK  even  though  it
>              doesn't know about the address.
>              ...
>              The authoritative statement
>                authoritative;
>                not authoritative;
>                The DHCP server will normally assume that  the  configura-
>                tion  information  about  a  given  network segment is not
>                known to be correct and is not authoritative.  This is  so
>                that  if  a  naive  user  installs a DHCP server not fully
>                understanding how to configure it, it does not send spuri-
>                ous   DHCPNAK  messages  to  clients  that  have  obtained
>                addresses from a legitimate DHCP server on the network.
>                Network  administrators  setting  up  authoritative   DHCP
>                servers  for their networks should always write authorita-
>                tive; at the top of their configuration file  to  indicate
>                that  the DHCP server should send DHCPNAK messages to mis-
>                configured clients.   If this is not done, clients will be
>                unable  to get a correct IP address after changing subnets
>                until their old lease has expired, which could take  quite
>                a long time.
>         regards,
>         -glenn
>         On 03/19/10 21:00, kalyan Alle wrote:
>             The DHCPNAK is sent by the windows DHCP server configured
>             but my device
>             with ISC dhcp-4.1.0 is unable to send the DHCPNAK.
>             Plz suggest if this is the expected behaviour or not.
>             -kalyan
>             On Fri, Mar 19, 2010 at 3:20 PM, kalyan Alle
>             <kalyan.alle at gmail.com <mailto:kalyan.alle at gmail.com>
>             <mailto:kalyan.alle at gmail.com
>             <mailto:kalyan.alle at gmail.com>>> wrote:
>                 I have got the issue with the setup as below
>                   *           (
>                    1) DUT(SU)(DHCP Server)----Ethernet0-----Win XP PC
>             (DHCP Client)
>                    2) Windows 2003 Server ( ----Eth----WIN
>             XP (DHCP Client)*
>                 *
>                 *
>                 *4) Enable the DHCP Server on DUT
>                 5) Make WinXP PC as Client and get the ip address (say
>                 6) Disconnect the DHCP Client PC and connect to windows
>             2003 Server i.e another
>                 DHCP Server configured on subnet.
>                 7) DHCP Client sends the DHCP request message with the
>             old ip address, DHCP
>                 server ( windows 2003 server) responds with DHCPNAK
>             message and after receiving
>                 DHCPNAK the client restarts the allocation procedure
>             with DHCPDISCOVER message.
>                 8) Clients gets ip address from Win server as
>                 9) Disconnect the DHCP Client and reconnect to Mumbai
>             SU/DUT.
>                 10)Again DHCP client sends the DHCP request message to
>             the DHCP server with
>                 assigned ip address which is in subnet to
>             DUT DHCP server.
>                 The DUT DHCP server is silent and doesn't send any
>             DHCPNAK message.
>                 Can any one comment or let me know the solution for this
>             scenario.
>                 thanks
>                 kalyan*

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