Meraki MX DNS

[HiroNg]

I curious how DNS work in Meraki. 

When configure Uplink in Meraki MX, i have configured dns provided by local telco. 

The MX is having vpn to our central office. 

I have configured internal DNS in user DHCP subnet. 

Question is here, how come telco DNS problem can cause user experience outlook office365 disconnected? 

Thank you. 

[kordm]

The MX DNS is a forwarder. If you point clients to use the MX as the internal DNS, it'll forward those requests to the DNS you have set on your WAN interface, unless you specify something else in the DHCP configuration.

Do you have a separate DNS server? Where is that server configured to forward DNS requests? If they all go to the telco DNS and if they're having an issue, connections will drop once the TTL of the domain name expires. For example, office365.com has a TTL of 5 minutes.

[HiroNg]

Hi, 

I have defined something else in the DHCP for the vlan i created. 

That is our internal DNS server, so i expect the client will query offce365 dns through our internal DNS instead of MX DNS. 

i just curious why the MX DNS problem will affect client connection to office365. 

Thank you. 

[kordm]

Where does your internal DNS server forward requests? It doesn't matter if clients are querying an internal DNS server if it is not authoritative for that zone, it will still forward the DNS lookup once the TTL of the A record expires.