Why do the switches need a public DNS Server to show up as green on the portal?

[RH6379]

We're installing 12 MS-120 switches in a remote office and the switches are showing a DNS misconfigured error when we use the IP of the mgmt vlan as the DNS Server.  That is configured on an MX84.  If I enter a secondary DNS Server IP of 75.75.75.75, they go from Yellow to Green on the portal.  What does having a public DNS IP on each switch buy me?  I can still get to the switches without it.

[jdsilva]

They don't need a public DNS server. I have lots that point to the private IP of my MX (that's also the DHCP server) and they work just fine. It's more likely that something is failing resolution using that DNS server.

[Adam]

They just need a valid DNS IP.  Whether internal or external.  Best practice is to just use an external IP since it is really only for the switches to check-in to the cloud.  

[JohnM]

---

@RH6379 wrote:

We're installing 12 MS-120 switches in a remote office and the switches are showing a DNS misconfigured error when we use the IP of the mgmt vlan as the DNS Server.  That is configured on an MX84. 

---

Is your MX84 not configured as a DNS proxy perhaps? If it's not relaying and returning DNS queries and responses for clients, then the switch isn't going to connect either.