[Dnsmasq-discuss] dnsmasq DHCP timing?

Gordon Croft Gordon.Croft@TELUS.COM
Tue, 14 Dec 2004 11:00:42 -0800


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Hello List...
We have a small LAN connected to the rest of the corporate network =
through a single router and have just got dnsmasq running on an Alpha =
box with Debian.  It seems to work great except for one thing.  When we =
enable the DHCP part and a client sends a DHCP Discover, the offers come =
back from other
DHCP servers past our router before the offer comes from dnsmasq.  We =
would prefer the offer came from the Alpha box first so we could take =
advantage of the dnsmasq's ability to cache DNS queries and lookup host =
names in the /etc/hosts file, ETC.  The offer from dnsmasq seems to take =
about one
second whereas the offer from the other servers is seen in milliseconds.

Is there some sort of configuration that tells dnsmasq to wait before it =
sends the offer?  We could, of course, go into the router and turn off =
the DHCP 'helper' function which is sending the DHCP offer to the other =
servers, but I'd rather not do that - I'd like to have the 'insurance' =
that comes
from multiple DHCP servers.

Any help appreciated.

Thanks,
Gord



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<P DIR=3DLTR><SPAN LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT =
SIZE=3D2 FACE=3D"Arial">Hello List</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">&#8230;</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"></SPAN></P>

<P DIR=3DLTR><SPAN LANG=3D"en-us"><FONT SIZE=3D2 FACE=3D"Arial">We have =
a small LAN connected to the rest of the corporate network through a =
single router and have</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"> <FONT SIZE=3D2 FACE=3D"Arial">just =
got</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> <FONT =
SIZE=3D2 FACE=3D"Arial">dnsmasq</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> <FONT SIZE=3D2 =
FACE=3D"Arial">running on an Alpha box with</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> <FONT SIZE=3D2 =
FACE=3D"Arial">Debian</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"><FONT SIZE=3D2 FACE=3D"Arial">.&nbsp; =
I</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT =
SIZE=3D2 FACE=3D"Arial">t seems to work great except for one =
thing.&nbsp; When we enable the DHCP part and a client sends a DHCP =
Discover,</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> =
<FONT SIZE=3D2 FACE=3D"Arial">the offers come back from other DHCP =
servers past our router before the offer comes from =
dnsmasq.</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us">&nbsp;<FONT SIZE=3D2 FACE=3D"Arial"></FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> <FONT SIZE=3D2 =
FACE=3D"Arial">We would prefer the offer came from the Alpha box first =
so we could take advantage of the dnsmasq</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">&#8217;</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"><FONT SIZE=3D2 FACE=3D"Arial">s ability to cache DNS =
queries and lookup host names in the /etc/host</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">s file, ETC.&nbsp; T</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">he offer from dnsmasq seems to take about one =
second</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> =
<FONT SIZE=3D2 FACE=3D"Arial">whereas</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial"> the offer from the other servers is seen in =
milliseconds.</FONT></SPAN></P>

<P DIR=3DLTR><SPAN LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT =
SIZE=3D2 FACE=3D"Arial">Is there some sort of configuration that tells =
dnsmasq to wait before it sends the offer?&nbsp; We could, of course, go =
into the router and turn off the DHCP</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> <FONT SIZE=3D2 =
FACE=3D"Arial">&#8216;</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"><FONT SIZE=3D2 FACE=3D"Arial">helper</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">&#8217;</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"><FONT SIZE=3D2 FACE=3D"Arial"> function which is sending =
the DHCP offer to the other servers, but I</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">&#8217;</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"><FONT SIZE=3D2 FACE=3D"Arial">d rather not do =
that</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> =
<FONT SIZE=3D2 FACE=3D"Arial">&#8211;</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial"> I</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"><FONT SIZE=3D2 FACE=3D"Arial">&#8217;</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">d like to have the</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"> <FONT SIZE=3D2 =
FACE=3D"Arial">&#8216;</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">insurance</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"><FONT SIZE=3D2 FACE=3D"Arial">&#8217;</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial"> that comes from multiple DHCP servers.</FONT></SPAN></P>

<P DIR=3DLTR><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"></SPAN></P>

<P DIR=3DLTR><SPAN LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT =
SIZE=3D2 FACE=3D"Arial">Any help appreciated</FONT></SPAN><SPAN =
LANG=3D"en-us"></SPAN><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">.</FONT></SPAN></P>

<P DIR=3DLTR><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">Thanks,</FONT></SPAN><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"></SPAN></P>

<P DIR=3DLTR><SPAN LANG=3D"en-us"><FONT SIZE=3D2 =
FACE=3D"Arial">Gord</FONT></SPAN></P>

<P DIR=3DLTR><SPAN LANG=3D"en-us"></SPAN><SPAN =
LANG=3D"en-us"></SPAN></P>

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