Iif you have some managed switches and routers on this network, just cross check the ip name-server command has got the right DNS ip address. Possibly these switches or routers have a different DNS ip assigned as the ip name-server. You could start by disabling the command using *no ip name-server* in global config mode.
On Tue, Feb 9, 2010 at 8:18 PM, Mike Barnard <[email protected]>wrote: > On Mon, Feb 8, 2010 at 5:19 PM, Emmanuel Sekyewa <[email protected]> > wrote: > > Mike, the DHCP server is running on Windows server 2003, will tcpdump > still > > apply in this case? I also changed the scope with reference to the new > > addressing scheme. > > Dan, it's a windows domain :-( > > There are a number of unmanaged switches on the network, if at all there > is > > any possibility that one of them could be supplying client machines with > a > > wrong entry, before the DHCP server does, how is it that this only > started > > happening after changing the addressing scheme? > > > > If you are using a Windows DHCP server, you *MUST* delete and recreate > a scope to suit your current setup. Of course this would not cause a > rouge DHCP server. ipconfig /all will show you the IP address of the > rouge DHCP server and then you can take it down. The other option is > to use group policies down to your computers to respond to DHCP > servers with a given option string in their DHCP offer. This way, you > make sure that they get IP addresses from the correct server only. > > tcpdump would still work, but you need to run it off a UNIX/Linux > installation. Im not sure whether there is a windows installation of > tcpdump. > > > > > > > > On 8 February 2010 16:38, Mike Barnard <[email protected]> wrote: > >> > >> On Mon, Feb 8, 2010 at 3:36 PM, Emmanuel Sekyewa <[email protected]> > >> wrote: > >> > Good afternoon, > >> > > >> > I'm in a situation in which after changing the IP addressing scheme on > a > >> > network, certain machines obtain a wrong entry for DNS at startup, but > >> > when > >> > I run an ipconfig /release and subsequently /renew, they pick up the > >> > correct > >> > settings/configuration for the DNS server. I have gone through my DHCP > >> > configuration a number of times to ensure that the correct IP > addresses > >> > are > >> > specified for the primary and secondary DNS servers, but this still > >> > keeps > >> > coming up. > >> > This even happens after flushing the DNS cache on a client machine and > >> > rebooting. > >> > Any ideas of what could be causing this? Or a viable work around? > >> > > >> > >> 1 -- what platform are you running you DHCP server? > >> 2 -- The quickest way to check whether you have another DHCP server on > >> the LAN is to run tcpdump and listen out for any bootp traffic. A > >> quick run of tcpdump -i <interface> -n port 67 or port 68 will show > >> you all bootp traffic on your LAN. > >> 3 -- If you did not change the scope on your DHCP server, you may end > >> up with some wrong info. > >> > >> > >> > >> -- > >> Mike > >> > >> Of course, you might discount this possibility, but remember that one in > >> a million chances happen 99% of the time. > >> ------------------------------------------------------------ > >> _______________________________________________ > >> LUG mailing list > >> [email protected] > >> http://kym.net/mailman/listinfo/lug > >> %LUG is generously hosted by INFOCOM http://www.infocom.co.ug/ > >> > >> The above comments and data are owned by whoever posted them (including > >> attachments if any). The List's Host is not responsible for them in any > way. > >> --------------------------------------- > >> > > > > > > > > -- > > Emmanuel C. Sekyewa > > > > +256 782 199 202 > > > > _______________________________________________ > > LUG mailing list > > [email protected] > > http://kym.net/mailman/listinfo/lug > > %LUG is generously hosted by INFOCOM http://www.infocom.co.ug/ > > > > The above comments and data are owned by whoever posted them (including > > attachments if any). The List's Host is not responsible for them in any > way. > > --------------------------------------- > > > > > > > > > > -- > Mike > > Of course, you might discount this possibility, but remember that one in > a million chances happen 99% of the time. > ------------------------------------------------------------ > _______________________________________________ > LUG mailing list > [email protected] > http://kym.net/mailman/listinfo/lug > %LUG is generously hosted by INFOCOM http://www.infocom.co.ug/ > > The above comments and data are owned by whoever posted them (including > attachments if any). The List's Host is not responsible for them in any way. > --------------------------------------- > >
_______________________________________________ LUG mailing list [email protected] http://kym.net/mailman/listinfo/lug %LUG is generously hosted by INFOCOM http://www.infocom.co.ug/ The above comments and data are owned by whoever posted them (including attachments if any). The List's Host is not responsible for them in any way. ---------------------------------------
