Does RBSXTR&R11e-LTE6 support passthrough?

RouterOS Wireless Networking
1

The documentation here https://wiki.mikrotik.com/wiki/Manual:Interface/LTE#Passthrough_Example says that

Warning: Passthrough is not supported by all chipsets.

But chipsets are not specified. The product home page https://mikrotik.com/product/sxt_lte6_kit#fndtn-specifications does not tell if this feature is available or not.

I have tried to do LTE passthrough with SXT LTE6 with a VLAN interface, but I couldn’t.

This is what I did:

/interface bridge vlan
add bridge=BR1 tagged=BR1,ether1-trunk  vlan-ids=100 comment="LTE"
/interface vlan
add interface=BR1 name=LTE_VLAN vlan-id=100
/interface lte apn
set 0 apn=net passthrough-interface=LTE_VLAN passthrough-mac=B8:69:F4:09:BE:F5
/interface lte
set 0 pin=1234

These are my vlan interfaces:

[admin@lte] /interface vlan> print detail
Flags: X - disabled, R - running
 0 R name="BASE_VLAN" mtu=1500 l2mtu=1594 mac-address=2C:C8:1B:79:49:1F arp=enabled arp-timeout=auto loop-protect=default
     loop-protect-status=off loop-protect-send-interval=5s loop-protect-disable-time=5m vlan-id=99 interface=BR1
     use-service-tag=no

 1 R name="LTE_VLAN" mtu=1500 l2mtu=1594 mac-address=2C:C8:1B:79:49:1F arp=enabled arp-timeout=auto loop-protect=default
     loop-protect-status=off loop-protect-send-interval=5s loop-protect-disable-time=5m vlan-id=100 interface=BR1
     use-service-tag=no

You can see that the mac address is 2C:C8:1B:79:49:1F. It certainly does not match passthrough-mac=B8:69:F4:09:BE:F5.

Nevertheless, the public IP is assigned to it:

[admin@lte] /ip address> print detail
Flags: X - disabled, I - invalid, D - dynamic
 0   address=192.168.14.251/24 network=192.168.14.0 interface=BASE_VLAN actual-interface=BASE_VLAN

 1 D address=5.204.180.93/30 network=5.204.180.92 interface=LTE_VLAN actual-interface=LTE_VLAN

The documentation also says, this:

In this configuration the router will not get IP configuration from the modem.

But it does. So maybe passthrough mode is not supported by this device?

2

Whew, this is strange. I can see that both devices have that public IP!

The local vlan interface on the LTE kit is assigned to the public ip. But also the vlan interface on the passthrough client is assigned to the same ip.

Is this normal? It contradicts the documentation (“In this configuration the router will not get IP configuration from the modem.”)

3

I am also experiencing the same behavior on both an R11e-LTE-US and R11e-LTE6-US. The work around I’ve done is add an additional default route in routing table with a higher priority than the primary default route. Then NAT all traffic the egresses the LTE interface.

4

I’ve used passthrough on LTAP, on LHGG, on WAP R, on WAP R with LTE6 on WAP AC with success…
Passthrough is a feature of the modem… Am not really sure why some chipsets do not support it and what is meant by that…

If you take a look here https://help.mikrotik.com/docs/display/ROS/Peripherals you will see that passthrough is a modem feature…

When you use passthrough, the modem just assigns an IP address to its eth or vlan interface ( depends on config )and creates a DHCP server for the client device to get an address… nothing more than that… There is no address to the LTE assigned, there is no access to the internet unless properly configured with a Route to the actual Router etc…

5

I can confirm that passthrough work on that device & lte module.
I setup it on SXTR passthrough often on ether2 bcs I use 2 ethernet cables to this unit and it’s not problem to use them both.
When customer have very good speed then only then I setup a bonding on eth1+eth2 with vlan passthrough, but second device must support bonding and vpn at WAN level, means any MikroTIk. We can receive more then 100Mbps with internet speed and have Public IP on second router who is always in my example hAP ac².

Of course a one Public IP can be hold at one device, network basics info.

BTW, MikroTik lte modules works in ECM mode without additional NAT, other vendors in this mode use NAT and even if ISP give you public IP you not see it and that’s why on some module the passthrough is no sense feature. Move lte module into MBIM (only ros7) bring a Public IP on lte card and we can passthrough it to next device.