So again, my requirement is to send a router value (default gateway) in response to ALL DCHP client DHCPDISCOVER requests coming in off interface vl20-ovsbr0 EXCEPT the one tagged "wanem-20" which should get NO (i.e. null) router option sent to it.
Empirically, the line I have (dhcp-option=tag:vl20-ovsbr0,tag:wanem-20,3) is working for me and does exactly the above. I suppose it is because that line means any machine (MACaddr) sending the DHCPDISCOVER message which is tagged both "vl20-ovsbr0" and "wanem-20" (which will be met by the WANem MAC addr alone) therefore meets the criteria of a null option 3 being sent. All other machines on that network (off the vl20-ovsbr0 interface) do not meet the criteria of this line (they are tagged "vl20-ovsbr0" alone) and therefore they get the default, which is to send the interface IP address that dnsmasq is listening on as DHCP option 3 (the default gateway.) Do I have this logic correct? Just trying to understand. The stanza dhcp-option=tag:vl20-ovsbr0,tag:!wanem-20,3 which says send an empty option 3 for hosts when "vl20-ovsbr0" is set AND "wanem-20" is NOT set, would do just the opposite, correct? (i.e. only the one machine with both tags set would recv a option 3 value, and the rest would NOT.) That would be the opposite of what I want to happen... Thanks again for your kind assistance and your replies... Will -----Original Message----- From: Simon Kelley [mailto:[email protected]] Sent: Wednesday, April 24, 2013 11:55 AM To: Will Dennis (Live.com) Cc: [email protected]; [email protected] Subject: Re: [Dnsmasq-discuss] Restrict DHCP providing default gateway to *one* host on one network On 24/04/13 15:52, Will Dennis (Live.com) wrote: > OK, this works - thanks TJ& Simon! > > So as I understand it, the line: > dhcp-option=tag:vl20-ovsbr0,tag:wanem-20,3 > means: for the machines tagged "vl20-ovsbr0" (which includes the WANem > machine's 2nd NIC), just use whatever the default option would be for > the router; but on machines tagged "wanem-20" (which matches ONLY the > WANem machine's 2nd NIC), set a NULL router option. > Correct? And, does order of application matter, or how else does > dnsmasq resolve the two options that match for the WANem VM's 2nd NIC? > dhcp-option=tag:vl20-ovsbr0,tag:wanem-20,3 says, send an empty option 3 for hosts when vl20-ovsbr0 AND wanem-20 are set. What you should have is dhcp-option=tag:vl20-ovsbr0,tag:!wanem-20,3 which says send an empty option 3 for hosts when vl20-ovsbr0 is set AND wanem-20 is NOT set. Since option 3 is in the set of options which dnsmasq sends by default, the meaning of "send an empty option 3" is subtly altered to "don't send option 3" Cheers, Simon. > Thanks again to everyone for their help in this! > > Best, > Will > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of > Simon Kelley > Sent: Wednesday, April 24, 2013 5:01 AM > To: [email protected] > Subject: Re: [Dnsmasq-discuss] Restrict DHCP providing default gateway > to > *one* host on one network > > On 24/04/13 08:58, TJ wrote: >> On 23/04/13 15:33, Will Dennis (Live.com) wrote: >>> interface=vl10-ovsbr0 >>> interface=vl20-ovsbr0 >>> bind-interfaces >>> dhcp-range=vl10-ovsbr0,192.168.10.50,192.168.10.150,4h >>> dhcp-range=vl20-ovsbr0,192.168.20.50,192.168.20.150,4h >>> dhcp-host=52:54:00:d5:ee:4d,id:*,192.168.10.1 >>> dhcp-mac=set:wanem-20,52:54:00:45:8c:6a >>> dhcp-option=vl10-ovsbr0,3,192.168.10.254 >>> dhcp-option=tag:vl20-ovsbr0,tag:!wanem-20,3,192.168.20.254 >>> log-dhcp >> >> I may be mis-reading the manual but as I understood it dnsmasq will >> issue a default set of options for each range. >> >> dhcp-range=vl20-ovsbr0 will get a default option 3 which will be the >> IP of the host running dnsmasq >> >> dhcp-mac=set:wanem-20 sets a tag for the exceptional client >> >> dhcp-option=tag:vl20-ovsbr0,tag:!wanem-20 will set a (possibly >> different) > gateway for non-exceptional clients. >> >> At this point the exceptional client will have the default option 3 >> for > the range. I think what you need is to not send any default route at > all when the exceptional client makes a request: >> >> dhcp-option=tag:vl20-ovsbr0,tag:wanem-20,3 > > I concur. Will, you've just omitted the empty option 3 from the last > dhcp-option. > > (Wanders off to teach dnsmasq to complain in this situation.......) > > > Cheers, > > Simon. > > _______________________________________________ > Dnsmasq-discuss mailing list > [email protected] > http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss > > _______________________________________________ Dnsmasq-discuss mailing list [email protected] http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
