[Dnsmasq-discuss] Dnsmasq switching to using secondary DNS exclusively

[JD]

On 08/17/2009 08:47 AM, Simon Kelley wrote:
> Michael Kraft wrote:
>    
>> I have a WRT54GLv1 with Tomato 1.25 on it.  Tomato uses Dnsmasq 2.47 for
>> DNS.  I realize the latest Dnsmasq is 2.49, but I don't see anything in
>> the change log related to what I'm seeing.   I have tomato set up to
>> cache DNS (150 entries) and handle the DNS queries itself.  This results
>> in a dnsmasq.conf of:
>>
>> pid-file=/var/run/dnsmasq.pid
>> interface=br0
>> resolv-file=/etc/resolv.dnsmasq
>> addn-hosts=/etc/hosts.dnsmasq
>> expand-hosts
>> min-port=4096
>> dhcp-range=192.168.1.100,192.168.1.149,255.255.255.0,10080m
>> dhcp-option=3,192.168.1.1
>> dhcp-lease-max=255
>> dhcp-authoritative
>> dhcp-host=00:13:CE:2A:1E:82,192.168.1.6,10080m
>>
>> The resolv.dnsmasq is:
>> nameserver 68.87.64.146
>> nameserver 68.87.75.194
>>
>> resolv.conf is:
>> nameserver 127.0.0.1
>>
>> So my primary DNS is 68.87.64.146 and my secondary DNS is 68.87.75.194.
>>
>> Every now and then the router starts using the secondary DNS
>> exclusively.  During this time the dnsmasq.conf and resolv.dnsmasq don't
>> change.  I can get the router to start using the primary DNS again by
>> killing and restarting Dnsmasq (or refreshing the DHCP release from my
>> ISP).
>>
>> It's my understanding that the secondary DNS should only be used if the
>> primary DNS doesn't answer the DNS query, but at the times I'm
>> experiencing the problem the primary DNS is responding to queries so
>> Dnsmasq should be using that.  There is nothing in the logs that seem to
>> indicate any kind of problem as far as I can tell.  The only log entries
>> I ever see relating to nameservers look like the following with the
>> secondary listed first and the primary listed second:
>>
>> Aug 11 23:55:55 ? daemon.info dnsmasq[23367]: using nameserver
>> 68.87.75.194#53
>> Aug 11 23:55:55 ? daemon.info dnsmasq[23367]: using nameserver
>> 68.87.64.146#53
>>
>>
>> Since my ISP's secondary DNS is a lot farther away geographically from
>> me than the primary, this not only slows down DNS queries, but causes
>> performance issues with Limelight, Akamai and any other server that
>> determines the server farm, by the DNS location.
>>
>> My question is why would Dnsmasq be switching to using the secondary DNS
>> exclusively and how (short of removing the secondary DNS server
>> manually) can I stop it from doing this?
>>      
>
> Dnsmasq doesn't treat these servers as primary and secondary - it
> considers them equal. The reason that the server in use changes is that
> dnsmasq sometimes sends a query to both servers, to see which one is
> fastest. Whichever replies first gets used until the next time the
> "race" gets run.
>
> You can change this behaviour with "strict-order", but be aware that
> will make performance much worse if the first server ever does fail.
>
>
> Cheers,
>
> Simon.
>
>    

That still does not explain why dnsmasq sticks with a nameserver that is 
slow???
Is it possible to have a config option that will force dnsmasq to switch 
server if no
response comes within a user-settable timeout?

JD