Possible bug when configuring multiple DNS servers with same IP address

[Bagpuss]

Hi All,

Just come across what I think might be a bug when configuring multiple DNS servers with same IP address.

If my case, I have multiple WAN/VPN interfaces available on my router.
In the past, I've configured pfSense to connect to the same DNS IPs using multiple different interfaces.

e.g.

208.67.222.222 - WAN1
208.67.222.222 - WAN2
208.67.220.220 - VPN1
208.67.220.220 - VPN2

Under previous versions of pfSense, the WebGUI would allow this with no problem.
However, I've just updated to 2.4.3, and when I try to save the DNS configuration after adding a new DNS server (in this case, I'm experimenting with Cloudflare), then I get "The following input errors were detected: Each configured DNS server must have a unique IP address. Remove the duplicated IP.".

I can understand this if the DNS servers were all configured to use the same outbound interface, but I'm not doing this.
I'm using different interfaces, so that DNS is still reachable if one of the interfaces goes down.

Is my thinking broken, or is this a bug?

Thanks,

Andy.

[johnpoz]

You only need to call out a specific dns if that dns is only available via that IP… Say an ISP dns that is only available when your connected to that ISP network.  Or a vpn dns that is only available via vpn connection.

Just using public dns there is no reason to call out specific interface that needs to be used.  Pfsense will use the connection it has that is working to get there.. Based upon your setup of which gateways to use depending on failure, etc etc..