LTE Failover with External LTE Modem Through PoE Switch

Hi everyone,

I hope to find some help around here even though I am planning a “not-Turris-only” setup. Also - hopefully - this topic may be interesting to others.

Current setup:

  • Turris Omnia connected through WAN interface (ethernet, not SFP) to modem provided by my ISP
  • a few devices connected to the LAN ports

Future :

  • a Cisco CBS250-24P-4G (PoE capable, passive cooling, VLAN capable) switch between the Turris Omnia and many more devices (server, TV, multiple access points, etc.) (switch to be purchased)
  • LTE failover :warning:

Using an LTE modem within the Turris Omnia is not an option, as the Turris Omnia will be placed “elsewhere” and therefore I want to place a LTE modem in a location with good reception and possibly no power outlet.

After a bit of research a Teltonika RUT240 LTE modem appears to be a good option.

Combined with the intention to purchase a PoE switch, I like to also power the LTE modem through the switch.

This is how I imagine the future setup:

Currently my questions focus on “what to research” for …

Questions:

  • Is this setup feasible?
  • Does anyone have experience with the Cisco CBS250-24P-4G and/or Teltonika RUT240?
  • One LAN port (lan4 in the image) needs to be reassigned to be a WAN interface, correct?
  • Is mwan3 (https://doc.turris.cz/doc/en/howto/multiwan) the correct tool?
  • What (e.g. key words) should I research, to enable the connection to/from the modem through the switch (probably I need another VLAN and some sort of routing…)
  • in short: what to I need. :slight_smile:

Notes:

  • The PoE splitter may not be necessary, not sure yet.
  • The switch should be connected to the Turris Omnia on lan0 acting as a VLAN trunk port
  • While in “failover mode” it is ok, if services offered by my network are not available to the outside world.
  • The key requirement is an (almost) uninterrupted connection from my network to the internet (for work/business purposes)
  • I also want the Turris Omnia to detect that no connection is available through WAN(1) for n seconds and then tell the LTE modem to establish a connection. One the connection through WAN(1) is available again, the Turris Omnia should tell the LTE modem to disconnect.

Thank you very much in advance!

I am using a similar setup with a DSL and a cable connection. I use MWAN3 for load balancing. I have no problems with that setup. Both providers ar up all the time (unless a problem occurs, of course).

If you run to different segments over one switch, as you do, you must separate the segments via VLAN. Otherwse you will have problems. Your CISCO-switch should support VLAN, but I am not familiar with the configuration of CISCO-switches. I am using ZYXEL-switches most of the time.

Hope this helps.

Hi @rwg,

thanks for your reply.

Good to know, that mwan3 is the tool to look for.

Do I understand correctly, that “simply” another VLAN needs to be set up (besides the assignment of a LAN port as a WAN port) - in my case - between the Turris Omnia router, the switch (which passes through the VLAN) and the RUT240?

Do you connect your cable and DSL line directly to the Turris Omnia or to the switch first?

In my “normal” setup I have one of the LAN-Ports changed to WAN2. So the DSL-Router is directly connected to the WAN-Port. The cable-router is directly conneted to the new WAN2-Port. I use the segments between router and Omnia as two seperate DMZ.

The Setup with a switch which is used for two different networks is used in a teachind environment. I seperate the two networks using port-based VLANs in the switch. Actually the router there is a Turris Mox. The VLAN config is only in the switch. The switch with 10 Ports is “split” in two switches with two ports and 8 ports using VLANs.

I will try to amke some sketches tomorrow. and post it here.

Ok, great, I’ll figure out, how to do that. (I saw the relevant topic a while ago.)

Could you elaborate on that? I don’t see yet, how DMZs play a role.

Understood!

That would be great! Thank you in advance.

Here is (simplified) my setup. I need two connections to the world because I do a lot of teaching from home.
Here is the rough setup (just using blocks).


Works fine for me.
The other setup is like this:
Turris2
This is a setup for teaching in a lab. The switch supplies Power to the Mox via PoE. The two VLANs separate The internet-side of the Mox from the LAN-Side. I made the setup to play with VLANs und to use the PoE.
You basically need a combination of the both setups.
Hope this helps.

Hi there,

@rwg thanks so much for the images. That explained a lot.

Definitely.

Conclusion for me regarding my questions from the first post:

Is this setup feasible?

Yes. :slight_smile:

One LAN port (lan4 in the image) needs to be reassigned to be a WAN interface, correct?

Yes.

Is mwan3 (https://doc.turris.cz/doc/en/howto/multiwan) the correct tool?

Yes.

Does anyone have experience with the Cisco CBS250-24P-4G and/or Teltonika RUT240?

Kind of open, but not in the scope of this forum.
It appears that (according to geizhals.at) at the time of writing the Cisco CBS250-24P-4G is not available. Well, I need to wait until it becomes available again … May be I’ll even go for the CBS250-24P-4X to have 10GBit/s on the SFP ports.

I also want the Turris Omnia to detect that no connection is available through WAN(1) for n seconds and then tell the LTE modem to establish a connection. One the connection through WAN(1) is available again, the Turris Omnia should tell the LTE modem to disconnect.

That is still open to me. Does anyone know, whether that’s feasible?

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