Best Configuration for a Mesh Network Connected to the T-Mobile Internet Device?

I have the same problem as cjb4 plus the xt8 drops the connection frequently; after researching it on the internet, found these possible causes.

1. Double NAT: Since T-Mobile's Home Internet likely uses its own router, connecting your ZenWifi XT8 to it creates a double NAT (Network Address Translation) scenario which can cause connectivity problems. This can be mitigated by putting the T-Mobile device in bridge mode (if supported) or disabling its wifi entirely.
2. MTU mismatch: T-Mobile's network might have a different maximum MTU (Maximum Transmission Unit) size than the default setting on your ZenWifi XT8. Try lowering the MTU on your ZenWifi XT8 to match T-Mobile's network (reported to be 1420). MTU: The Maximum Transmission Unit(MTU) of PPPoE packet. The default value is 1492
3. IPv6 issues: There have been reports of trouble with the ZenWifi XT8 getting an IPv6 address from T-Mobile's network. Asuswrt-Merlin firmware may offer more configuration options for IPv6 than the stock Asus firmware.  

I tried disabling the WiFi on the gateway, it did not fix the issue.  I think the issue is #2.  Asus software does not have the ability to change the MTU value.  Asuswrt-Merlin firmware does but I couldn't find a version specific to the XT8.

#3 I turned off IP V6 in the adapter settings there is still significant performance drop 170Dn 16Up.  When I connect to the XT8 router using ethernet cable the performance is terrific 360Dn 15Up

Thank you for the reply.

To be honest I gave up.  While the T-Mobile internet provides decent speeds it isn't as stable as I would like for a mesh system.  I went back to comcast with a one year contract on 1 gig service while T-Mobile stabilizes their systems.  My nesh network is arrayed across 4 levels in my house.  My TV room is in the bottom level and that's the problem.  T-Mobile would go down almost daily for 20 or 30 seconds, while not a problem with direct connections it takes upwards of 7-10 minutes to come back up with my mesh network.  Too annoying! Will tty again in a year. 

cjb4 wrote:

I have a Asus mesh network with a Asus GT-AX11000 and two Asus ZenWiFi xt8s connected to the TM Internet device.  I am getting good speeds from the TM modem (250-350 Mbps) which then translates to 150-250 Mbps from the mesh network.  I had the mesh network connected to a cable modem with Comcast service which I discontinued when I found I could get decent speed from TM internet.  

Did you ever get this fix? I am thinking about buying the  Asus ZenWiFi xt8 2 pack if they work with the T-Mobile Home Internet Gateway. I have the "trash can"