[Dnsmasq-discuss] using dnsmasq with 4 upstream servers

Daniel Steglich daniel at steglich.bz
Fri Sep 2 12:23:44 BST 2016


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Hi,

I've got 4 upstream DNS Servers from my ISP (2 IPv4, 2 IPv6) and use 
all of them in /etc/resolv.conf.
I start sending DNS SRV querys from a client to dnsmasq DNS relay every 
5 seconds.

Each request is sent to four DNS upstream servers (primary DNS v4, 
secondary DNS v4, primary DNS v6, secondary DNS v6). The answer from the 
fastest server is used.
As the requests are DNS SRV records, the reply is not cached by 
dnsmasq.

During my tests the first IPv6 DNS server was always the fastest 
replying server and for this reason the answer from this server is 
passed to the client always,
After some time the dnsmasq relay is not forwarding the requests to the 
four known DNS servers any more but only sends out the requests to 
either the first IPv4 DNS server or the first IPv6 DNS server. So only 
one server is used. After about 20 seconds (4 requests later) the 
dnsmasq process falls back to the expected behaviour of sending the 
request to all known DNS Servers.

does anybody knows the reason for this?

- ---
Mit freundlichen Grüßen

Daniel Steglich
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