I have a problem with the isolation level of my DECO network.

The setup: 

• 3x DECO running in AP mode 
• Router : ER605 
• Windows Server 2025 running as DNS

The Deco's are configured to have

• Main network 2,4ghz + 5ghz
• Guest Network with LAN Disabled (2,4ghz) 
• IOT network 2,4ghz

This creates a proble for all GUESTS , since they cant access the DNS server 

so all im asking for is one of 3 solutions:

A: Allow port 53 on TCP/UDP to the DNS server from GUEST network. 

or

B: Override DHCP 006 DNS or DHCP setting for Guests and specify a public DNS server like 1.1.1.1 or 8.8.8.8

or 

C: Use Router / NAT features in the DECO x55 but only for Guest network , simply create it's own subnet with a totally different ip range than the Main and IOT network. 

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B would be prefered if possible then C and then A