How can clients use different dns servers

[Peter-DG]

Hi,

If I have 2 vlans on MX with DNS settings in DHCP are all set to proxy to upstream DNS, and 2 wan ports with internet connections (different ISPs), could I make the clients who connecting to wan2 using WAN2's DNS servers, not the primary uplink (wan1) DNS.

sorry maybe I'm not clear enough because I don't know how to describe it.

thanks,

Peter

[Shubh3738]

Which DNS are you using?

Is any AD DNS ?

If not you can use google dns for both isps 8.8.8.8

[jimmyt234]

Documentation states the following: "Clients will send DNS requests to the LAN interface of the MX, which will then proxy those requests to the DNS server(s) configured for its primary Internet uplink."

So, unless you set WAN 2 as the primary uplink then clients using a flow preference to use WAN 2 will actually be using WAN 1 DNS.

Alternatively, you can change DHCP settings and set your own preferred DNS servers to the clients (e.g. Google or Umbrella), rather than using the configured uplink ones.

[Peter-DG]

Thanks @jimmyt234 ! 

Yes I've changed the DHCP settings now, and I can see the DNS requests are sending to the DNS server I set in DHCP DNS settings. But a weird thing is: I can open Google now-before I changed the DNS settings I can not-but all my pings to Google failed. So why does this happened?

THanks,

[Peter-DG]

OK I called MEraki support and their engineer told me all icmp request are directing to primary uplink, so even I added the flow preferece to forward vlan 20 traffics to WAN 2, the icmp packages are sent to WAN 1 since WAN1 is my primary uplink. that's why I can't ping google but I can open google.

[jimmyt234]

Weird. Can they link to some documentation that describes this behaviour? Having ignoring the flow preference rule?

[Caleb-Engle]

Hi @jimmyt234,

This is documented as expected behavior in the MX Load Balancing and Flow Preferences KB:

"Note: ICMP traffic is not subject to traffic shaping rules. As a result, Flow Preference will have no impact on ICMP traffic."

[jimmyt234]

Thank you @Caleb-Engle! 😀