Issues with the "change DNS if Pi-hole is no longer working" script

broderick · Thu Feb 10, 2022 11:58 am

Hi ,
I use the script which automatically changes DNS if Pi-hole is no longer working"

:local currentDNS [/ip dns get server]
:local piholeDNS "192.168.3.12"
:local backupDNS "1.1.1.1,1.1.1.2"
:local testDomain "www.google.com"

:if ($currentDNS = $piholeDNS) do={
    :do {
        :resolve $testDomain server $piholeDNS
    } on-error={
        /ip dns set servers=$backupDNS
        /ip dhcp-server network set [find] dns-server=$backupDNS;
    }
} else={
    :do {
        :resolve $testDomain server $piholeDNS
        /ip dns set servers=$piholeDNS
        /ip dhcp-server network set [find] dns-server=$piholeDNS;
    } on-error={}
}

More details here:

viewtopic.php?t=161785

It works flawlessly, but I'd like it not to change also DNS IPs in " /ip dns>" which should always be set as 1.1.1.1 and 1.1.1.2.
I need that only the DNS server in

/ip dhcp-server network

should switch between 192.168.3.1 (my router Ip) and 192.168.3.12 (my pihole ip address) when the server in which pihole is installed is down.
Could you help me change it..if possible?
Thanks

Sob · Thu Feb 10, 2022 2:08 pm

Just remove the lines starting with "/ip dns set servers=".

But relying on DHCP is not very good solution. Let's say that client first gets Pi-hole as resolver. Then it goes down, so you change DHCP settings, but that won't change client's config immediatelly, it will only happen when it renews DHCP lease. It can take several minutes or even hours, depending on configured lease time. And same thing will happen when client has backup server and Pi-hole becomes available again.

broderick · Thu Feb 10, 2022 3:20 pm

Just remove the lines starting with "/ip dns set servers=".

But relying on DHCP is not very good solution. Let's say that client first gets Pi-hole as resolver. Then it goes down, so you change DHCP settings, but that won't change client's config immediatelly, it will only happen when it renews DHCP lease. It can take several minutes or even hours, depending on configured lease time. And same thing will happen when client has backup server and Pi-hole becomes available again.

ok, I'm going to test it either way, and see what is going to happen exactly.
I wanted DNS-SERVER in ip dhcp-server network to switch to my router IP 192.168.3.1 (while dns set back to 1.1.1.1 and 1.1.1.2) when pihole is down, just to enable my mikrotik device to use the cache.

Thanks

Issues with the "change DNS if Pi-hole is no longer working" script

Issues with the "change DNS if Pi-hole is no longer working" script

Re: Issues with the "change DNS if Pi-hole is no longer working" script

Re: Issues with the "change DNS if Pi-hole is no longer working" script

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