I spent a lot of hours solving that issue so here goes (firmware version: 3.0.0.4.382_50010).
I have an RT-AC87U connected to an ISP through a modem in bridge mode. I then have a Windows 10 client on the 5 GHz interface.
Then problem I had is that UPNP IGD (that is used to automatically open ports in the NAT) was very unreliable. It would work fine after the router was booted then stop working after a couple of minutes (ie. the clients would not be able to punch holes in the NAT anymore...
ASUS RT-AC87U UPNP IGD not working because of IGMP problems
I have an RT-AC87U connected to an ISP through a modem in bridge mode. I then have a Windows 10 client on the 5 GHz interface.
Then problem I had is that UPNP IGD (that is used to automatically open ports in the NAT) was very unreliable. It would work fine after the router was booted then stop working after a couple of minutes (ie. the clients would not be able to punch holes in the NAT anymore...
ASUS RT-AC87U UPNP IGD not working because of IGMP problems