[Dnsmasq-discuss] Further thoughts/questions on failover

Michael michael at kmaclub.com
Thu Sep 2 17:44:48 UTC 2021


On 9/2/21 6:58 AM, Kevin Tedder wrote:
> Chris
> You just need to update the /etc/resolv.conf file on each of your clients to
> point them at both DNS's.
>
> e.g
> nameserver 192.168.1.2
> nameserver 192.168.1.3
>
> The client will now ask both DNS servers. It will get a response even if one
> of them is off-line.


This is generally platform specific.   Not all resolvers treat things 
equally.    Some will only query one and if it times out, then will go 
to the other.   This can cause big delays in DNS resolution and ends up 
feeling like your whole network is slow. Others query both and take the 
fastest response, so it is hit or miss based on your client platforms.


Additionally, if the dnsmasq instance is ONLY doing DNS service, this 
can work fairly well.   Keep the hosts file replicated and either server 
can hand out the same data.  Obviously the cache will be different for 
each so you loose some effectiveness, but the client never really knows.


However, if you are running DHCP and dnsmasq is updating/maintaining a 
list of host names of your local clients in the leases file, then only 
one of the dnsmasq instances is going to know about those.    In this 
instance, I think makes more sense to ensure you have one really robust 
dnsmasq system than having two that don't respond the same.


I think both have valid use cases and it just depends on what works best 
for your scenario.


Michael






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