Hi my isp doesn't provide bridge mode on the ONT+router combo, because of this i have to use my asus ax58u on ap mode and it works fine my only problem is that a lot of the features like vpn don't show up on ap mode. Is there any firmware or hack to be able to use this features on ap mode? I wanted to avoid using a raspberry pi for vpn server when my router is capable of doing it
Double NAT works fine where you run VPN clients on the second router. No need for DMZ. I have even experimented and gone as deep as QUAD NAT with no problems. Double NAT only creates problems/challenges if you need or want to run some type of server on the second router.
Also being double NAT will not increase the latency by a amount that SOHO users can measure.
The biggest issue when running double NAT and you have a network problem the support people will blame in on the double NAT and stop looking for what is the real problem.
If you have the ISP modem/router in Bridge Mode though the support people will blame your equipment instantly and ask you to revert the ISP equipment to Router mode for further diagnostics. Many Asus router users called the ISP for no reason after their Asus router fail to obtain WAN IP from DHCP.
This is exactly an option for people who have to run the ISP provided equipment in Router mode for VoIP, IPTV or whatever other reason.
Connect your own router's WAN port to a LAN port of the ISP router. The ISP router's DHCP will assign an IP for your own router. This IP becomes WAN IP for your own router. This IP has to be placed in ISP router's DMZ. It's only needed if you run some services accessible from Internet on your own router. You either forward specific ports manually or use DMZ for convenience. If nothing needs port forwarding you can skip this part and it will still work.