Hi .. I have now managed to pass the LHG LTE management interface to the USG .. Many thanks to Sabastia for all the hints and guidance!!


My setup for reference

Internet -----> LHG 4G (ether1 VLAN100)----->Ubiquiti USG WAN (eth0.100) - DHCP client enabled
LHG 4G Mgt (10.0.0.1) -----> Ubiquiti USG WAN (eth0 10.0.0.2) - DHCP client enabled

USG config.gateway.json

{
"interfaces": {
"ethernet": {
"eth0": {
"address": ["dhcp"],
"description": "LTE Modem",
"duplex": "auto",
"speed": "auto",
"vif": {
"100": {
"address": [
"dhcp"
],
"description": "WAN",
"dhcp-options": {
"client-option": [
"retry 60;"
],
"default-route": "update",
"default-route-distance": "1",
"name-server": "no-update"
}
}
}
}
}
},
"service": {
"nat": {
"rule": {
"5000": {
"destination": {
"address": ["10.0.0.1"]
},
"outbound-interface": ["eth0"],
"type": "masquerade"
}
}
}
}
}

Just to give my two cents on this subject as I had been struggling with this too. Also, I needed the LHG device for my rural estate and this will be just for home/home office.

This is purposely kept very basic and aimed to help people to get LTE passthrough and the management working while using Mikrotik and Ubiquiti devices.

To keep things simple I have sticked to the 192.168.1.0/24 (255.255.255.0) addressing.

Anyway, I have the following devices:
LHG LTE6
Ubiquiti USG 3P
Ubiquiti USW Flex Mini (any simple switch should do as long as it supports basic VLAN traffic).

I have set them up so:
LHG LTE6 eth1 to eth1 of USW Flex Mini (a simple switch)
USW Flex Mini eth2 to USG 3P WAN
USW Flex Mini eth3 to USG 3P LAN1


I also have some more Ubiquiti gear that I will add later when I actually get around to it. Then use LAN1 on the USG as management network and LAN2 on the USG for else.
Also, I am quite sure that on the UDM Pro you can do a more elegant solution - the USG 3P and Flex Mini have some hardware restrictions.


On the Ubiquiti UI side

Under Internet -> WAN Networks you have:
IPv4 Connection Type: Using DHCP (so that the LTE IP can be passed to it)
Use VLAN ID 30 (or whatever number you want to use) and have it Enabled.

Under Networks -> Local Networks
Gateway IP/Subnet 192.168.1.1/24
DHCP Mode: DHCP Server

You can play with the Port Profiles, but just make sure everything works before and leave them to All for the time being.



On the Mikrotik
I removed the entire default config after a reset.
The Quick Set view of the working setup can be seen like this:

I use the 192.168.1.3 as a fixed IP to manage the Mikrotik LHG.

In ther Interfaces menu you have to create a VLAN for LTE passthrough (I have it VLAN already created but you should only have LTE and eth1 there):




I use VLAN 30 for that:


Interface List tab:



Under IP and Addresses you should assign a static IP as your management (or you can set up a DHCP client for eth1):

If you have done things correctly on the Ubiquiti side then you might get disconnected but you should be able to use the 192.168.1.3 IP or Winbox to reconnect directly using your computer.

This should be created automatically once you assign the LTE to pass traffic through the VLAN, but just to check later if you are having problems. The VLAN interface should act as a DHCP server to the USG WAN interface:



After that you should be ready to change the LTE APN to passthrough over the VLAN interface:



Hopefully this will help someone in the right direction.

Just to give my two cents on this subject as I had been struggling with this too. Also, I needed the LHG device for my rural estate and this will be just for home/home office.

This is purposely kept very basic and aimed to help people to get LTE passthrough and the management working while using Mikrotik and Ubiquiti devices.

To keep things simple I have sticked to the 192.168.1.0/24 (255.255.255.0) addressing.

Anyway, I have the following devices:
LHG LTE6
Ubiquiti USG 3P
Ubiquiti USW Flex Mini (any simple switch should do as long as it supports basic VLAN traffic).

I have set them up so:
LHG LTE6 eth1 to eth1 of USW Flex Mini (a simple switch)
USW Flex Mini eth2 to USG 3P WAN
USW Flex Mini eth3 to USG 3P LAN1


I also have some more Ubiquiti gear that I will add later when I actually get around to it. Then use LAN1 on the USG as management network and LAN2 on the USG for else.
Also, I am quite sure that on the UDM Pro you can do a more elegant solution - the USG 3P and Flex Mini have some hardware restrictions.


On the Ubiquiti UI side

Under Internet -> WAN Networks you have:
IPv4 Connection Type: Using DHCP (so that the LTE IP can be passed to it)
Use VLAN ID 30 (or whatever number you want to use) and have it Enabled.

Under Networks -> Local Networks
Gateway IP/Subnet 192.168.1.1/24
DHCP Mode: DHCP Server

You can play with the Port Profiles, but just make sure everything works before and leave them to All for the time being.



On the Mikrotik
I removed the entire default config after a reset.
The Quick Set view of the working setup can be seen like this:

I use the 192.168.1.3 as a fixed IP to manage the Mikrotik LHG.

In ther Interfaces menu you have to create a VLAN for LTE passthrough (I have it VLAN already created but you should only have LTE and eth1 there):




I use VLAN 30 for that:


Interface List tab:



Under IP and Addresses you should assign a static IP as your management (or you can set up a DHCP client for eth1):

If you have done things correctly on the Ubiquiti side then you might get disconnected but you should be able to use the 192.168.1.3 IP or Winbox to reconnect directly using your computer.

This should be created automatically once you assign the LTE to pass traffic through the VLAN, but just to check later if you are having problems. The VLAN interface should act as a DHCP server to the USG WAN interface:



After that you should be ready to change the LTE APN to passthrough over the VLAN interface:



Hopefully this will help someone in the right direction.

Just to give my two cents on this subject as I had been struggling with this too. Also, I needed the LHG device for my rural estate and this will be just for home/home office.

This is purposely kept very basic and aimed to help people to get LTE passthrough and the management working while using Mikrotik and Ubiquiti devices.

To keep things simple I have sticked to the 192.168.1.0/24 (255.255.255.0) addressing.

Anyway, I have the following devices:
LHG LTE6
Ubiquiti USG 3P
Ubiquiti USW Flex Mini (any simple switch should do as long as it supports basic VLAN traffic).

I have set them up so:
LHG LTE6 eth1 to eth1 of USW Flex Mini (a simple switch)
USW Flex Mini eth2 to USG 3P WAN
USW Flex Mini eth3 to USG 3P LAN1


I also have some more Ubiquiti gear that I will add later when I actually get around to it. Then use LAN1 on the USG as management network and LAN2 on the USG for else.
Also, I am quite sure that on the UDM Pro you can do a more elegant solution - the USG 3P and Flex Mini have some hardware restrictions.


On the Ubiquiti UI side

Under Internet -> WAN Networks you have:
IPv4 Connection Type: Using DHCP (so that the LTE IP can be passed to it)
Use VLAN ID 30 (or whatever number you want to use) and have it Enabled.

Under Networks -> Local Networks
Gateway IP/Subnet 192.168.1.1/24
DHCP Mode: DHCP Server

You can play with the Port Profiles, but just make sure everything works before and leave them to All for the time being.



On the Mikrotik
I removed the entire default config after a reset.
The Quick Set view of the working setup can be seen like this:

I use the 192.168.1.3 as a fixed IP to manage the Mikrotik LHG.

In ther Interfaces menu you have to create a VLAN for LTE passthrough (I have it VLAN already created but you should only have LTE and eth1 there):




I use VLAN 30 for that:


Interface List tab:



Under IP and Addresses you should assign a static IP as your management (or you can set up a DHCP client for eth1):

If you have done things correctly on the Ubiquiti side then you might get disconnected but you should be able to use the 192.168.1.3 IP or Winbox to reconnect directly using your computer.

This should be created automatically once you assign the LTE to pass traffic through the VLAN, but just to check later if you are having problems. The VLAN interface should act as a DHCP server to the USG WAN interface:



After that you should be ready to change the LTE APN to passthrough over the VLAN interface:



Hopefully this will help someone in the right direction.

Just to give my two cents on this subject as I had been struggling with this too. Also, I needed the LHG device for my rural estate and this will be just for home/home office.
----
Hopefully this will help someone in the right direction.

I would post one small update to the guide - if you will ever plan to put switch aware of vlans (Flex mini doesn't care about them), between LHG and USG you will need to add network in ubiquiti with matching VLAN ID - it can be even one host only like 192.168.2.1/30 disable DHCP on network and you are done.

Zrzut ekranu_20230123_172314.png

Verification on switch.

Zrzut ekranu_20230123_172602.png

I had a massive headache with adding USW-8 without VLANS it won't work