3G/4G LTE PPP vs. Direct IP: A noticeable difference in speed

[boomer]

Hello fellow Billionaires. It was while testing my new Huawei E3372s modem on my 8900X R3 router that I noticed the pronounced difference in speed between running the modem on stick vs. HiLink firmware (PPP vs. Direct IP under the Type column in Status > WAN). Download speed is particularly affected, dropping from an average of 55-60 mbps to a mere 15-17 mbps in PPP mode. Upload speed is comparable for both connection methods at about 20-25 mbps. Interestingly, running the modem as a PPP dialup connection vs. cellular connection (via network card) in Windows does not seem to affect speed and both connection methods provide comparable download speeds in excess of 60 mbps during low congestion hours.

I ran my tests on the 8900X using the patched UK f/w 2.52.d14_0323 since this is the most up-to-date version which supports this modem. The results are identical on original firmware.

I would like to run the modem in stick (PPP) mode since this allows port forwarding, which is unfortunately not possible in Hilink (Direct IP) mode since this activates the modem's NAT. Does anybody know if it's possible to tweak the router's PPP client so it will provide a download speed closer to the modem's capacity? Many thanks in advance.

[boomer]

Hi guys. I was able to work around the problem of maintaining full LTE speeds by running the modem in routed mode (Direct IP) while still performing port forwarding: The solution was to set up port forwarding rules twice - once on the modem and once on the router, forwarding traffic to the router in the former and to the client in the latter case. It's a somewhat cumbersome method which precludes UPnP port forwarding since UPnP requests are not propagated across interfaces. Furthermore, the router appears to disable UPnP port forwarding altogether when the connection type is Direct IP.

Note that implementing this solution on this particular modem required replacing the modem's factory original web interface with a more advanced version which provides port forwarding. Fortunately I was able to find such an interface on the web.

I would prefer running the modem in serial (PPP) mode despite this workaround since this would simplify the port forwarding procedure dramatically, so I'm still looking for a solution to the speed problem in PPP mode. Any ideas are welcome. Cheers.

Edit: The modem's web interface turns out to provide a DMZ option which simplifies the port forwarding procedure somewhat. Still, UPnP port forwarding is not possible in Direct IP mode.