LTE passthrough with MBIM modems

RouterOS General
1

Hey there,

I’m testing ROS 7.13.1 with an Alcatel IK41VE (MBIM mode). Works great with default settings, but I can’t get passthrough to work properly. I did set the passthrough interface to ether1. The device connected to that interface does indeed get public IPv4 (DHCP) and IPv6 (SLAAC) addresses, gateways and DNS servers, but the router won’t route any traffic. For IPv4, the gateway responds with ICMP destination network unreachable. For IPv6, the advertised gateway doesn’t even respond to Neighbor Solicitations.

Am I doing something wrong, might this be an issue with this specific modem or is MBIM passthrough just broken? The docs say “passthrough is not supported by all chipsets”, but I can’t find any official information about supported driver types (PPP / MBIM / RNDIS / …).

Cheers
Maurice

2

This turned out to be neither a configuration error nor an issue with MBIM or this specific modem. Originally, I evaluated RouterOS x86 (which I probably should have mentioned), ether1 is an Intel 82567LM NIC. This works fine for routing, but not for LTE passthrough (issues see above).

Now I bought a hEX S (RB760iGS) and repeated the test. Same LTE modem, same RouterOS version, same configuration - and it works!

So to answer my own question: LTE passthrough with generic MBIM modems is supported, but apparently broken in the x86 build of RouterOS.