[Dnsmasq-discuss] Intermittent DNSMASQ resolution failures

[Stuart Wilson]

Noticed after sending the original email, the version I am using is 
2.57. Could an upgrade fix this issue?

/*Regards,
Stuart

*/
On 02/15/2013 01:32 AM, Stuart Wilson wrote:
> Hi,
>
> I have noticed lately on several machines using the local cable ISP in 
> my neck of the woods, that using the DHCP supplied DNS servers from my 
> ISP is significantly slower than using a global DNS service like 
> OpenDNS. With that in mind I configured the Linux box I use at home to 
> use OpenDNS. It was working great, until I decided to fix it by adding 
> DNSMASQ as a local caching server to lighten the load. It works fine 
> most of the time, but sometimes I get intermittent failures to resolve 
> names. At first I just noticed delays getting to some websites, and 
> occasionally it would fail entirely. At times though it became 
> unacceptable and failed a lot. So, I started testing name resolution 
> in a shell using the "host" command, and found that it did indeed 
> sometimes give me a ";; connection timed out; no servers could be 
> reached" error. When I specifically ask the host command to query the 
> OpenDNS server directly, bypassing DNSMASQ, it never fails and is 
> always very fast.
>
> I got really curious about this and captured some packets with 
> Wireshark. First of a host query going through DNSMASQ that failed, 
> and then one going directly to the DNS server. I did indeed get no 
> reply back on the query that failed. The only difference I could find 
> between the packets being sent to OpenDNS by DNSMASQ, and those going 
> direclty from the OS to OpenDNS, is that the queries that failed from 
> DNSMASQ had the DF (don't fragment) bit set. Now it is quite possible 
> I'm missing something here, but it occurs to me that my using DNS 
> servers half way across the internet, rather than right down the 
> street at the local ISP, could be causing packets with the DF bit set 
> to get dropped. Is there any way to tell DNSMASQ to not set the DF 
> bit? Can anyone think of another reason why this is failing for me?
> -- 
>
> /*Regards,
> Stuart
>
>
> */
>
>
> _______________________________________________
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss at lists.thekelleys.org.uk
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/attachments/20130215/e778f494/attachment.html>