bilinmiyor

it shows open nat however using traceroute gives me both local ips. first netduma then main router

yes open and single nat

yes r2 wan ip in my router's DMZ. ISP modem is in bridge mode.

I disabled ipv6 until an ipv6 relay feature. However, I got double NAT despite DMZ on my main router.

Yes exactly, only ipv6 dhcp relay solves the problem

for ex: main router subnet 192.168.3.x and netduma subnet 192.168.4.x main router get /64 prefix (3.x) itself and assign an ipv6 to netduma, however netduma cannot get a prefix ipv6. In this situation, netduma cannot assign ipv6 to its subnet (4.x) as well as PC. I need /56 prefix or something for more subnet prefixes but my ISP provides only /64

Yes definitely, but main router cannot delegate ipv6 prefix because of /64 which supports only 1 subnet. Is there any option like dhcp relay for LAN devices?

yes 2 different internet service providers both connected to main router's different wan ports.

I have 2 ISPs connected to main router. Some devices use ISP1 and some use ISP2. Running fully configured QoS, bandwidth control, load balancing between ISPs etc. Also running pihole dns server with conditional forwarding over subnet. But most important thing is my ISP provides /64 prefix ipv6. So it supports only 1 subnet.

Yes exactly what I want.

Hello, I just got my Netduma R2. My setup: Modem --- Main Router(192.168.3.x subnet) ---- Other Devices, APs ---- Netduma R2 --- Only my gaming PC I want my gaming PC stay in main router subnet and netduma control only my PC. What do I need to do? Thanks in advance