Where does the IP address in the " Inherit IPv4 DNS Settings Dynamically from WAN Zone" come from?

AvacadoToastK12

Hello All

I am a new systems administrator for a k12 school and we have been having some DNS issues lately. I have found in the sonicwall settings, it is pointing to a DNS server that we no longer have (see picture). As I was left with no documentation, I was wondering where the firewall gets this IP from? Thank you for the help!

I have an NSa 2650

BWC

@AvacadoToastK12 they should usually match with the DNS settings from your first WAN interface, which is usually X1.

This might cause trouble if you're having multiple WAN connections from different providers and the firewall is using a provider specific DNS resolver which is not accessible from other networks and the primary WAN is failing.

It's probably best to have a provider independant setting on the Firewall, like 8.8.8.8, 8.8.4.4, 9.9.9.9, 1.1.1.1 etc. ... the usual suspects or run your own resolver.

--Michael@BWC

AvacadoToastK12

Ahhhh. I see! But that poses another question (and forgive me if this is outside realm of the forum): Why have a local DNS IP for a WAN interface? Is that the problem you are referring to?

BWC

@AvacadoToastK12 the DNS on the WAN Interface makes sense if we're talking dynamic assignment, like through DHCP or PPPoE. With a single WAN Interface this might be fine and the Firewall is getting the DNS information from the provider.

But the problem arises if your X1 is connected to German Telekom and X2 is connected to Vodafone (god forbid) for example. X1 might be your primary interface and the Firewall is using therefore the DNS assigned from X1, but when X1 fails all requests getting routed via X2 and the German Telekom might now allow DNS requests from other networks.

This is where statically configured open DNS resolvers like from the data hog Google etc. come in handy.

--Michael@BWC