[Dnsmasq-discuss] Active-passive failover for dnsmasq with ldirectord

Tom Fernandes anyaddress at gmx.net
Wed Jan 29 21:32:28 GMT 2020


Hi again,

are there some points in my description that are unclear?

Feedback concerning this setup is very much appreciated!

Warm regards,


Tom

On 23/01/2020 15:08, Tom Fernandes wrote:
> Hi,
>
> I read the old threads regarding dnsmasq and high availability and would
> like to know if the following setup is possible or if I'm missing something.
>
> Master: dnsmasq A (192.168.1.10)
> Slave: dnsmasq B (192.168.1.20)
>
> Loadbalancer virtual IP in ldirectord 192.168.1.30
>
> The clients use the virtual IP 192.168.1.30 as their nameserver.
>
> Host A is a "normally" configured dnsmasq server which also offers DHCP.
>
> Host B is configured the same way like server A with addition of an
> iptables rule which blocks incoming DHCP-Requests.
>
> The configuration files + the DHCP leases file are on a shared
> (active-active) Cluster-FS available to A and B.
>
> ldirectord is configured with with one realserver (A) and one fallback
> server (B). In this configuration a connection to 192.168.1.30 will only
> lookup records from host A (as long as A is alive).
>
> When A goes down, the following will happen:
> 1) The fallback server B will be used when clients lookup records from
> 192.168.1.30
> 2) The loadbalancer will connect (through ldirectords "fallbackcommand"
> with the "start" parameter) via SSH to server B and remove the iptables
> rule which blocks incoming DHCP requests and will restart dnsmasq.
>
> Now server B is offering DHCP and DNS requests in the same way like
> server A was doing before.
>
> When server A gets online again the "fallbackcommand" on the
> loadbalancer is called again (this time with the "stop" parameter). It
> will now connect to server A and restart dnsmasq and to server B and set
> the iptables rule again to block incoming DHCP requests. Server B will
> become the fallback server again.
>
> What do you think?
>
> Warm regards,
>
>
> Tom
>
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