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Getting Started with Cellular Modems

This document describes how to connect, provision, and configure the Lantronix Local Manager for use with external or embedded cellular modems for out-of-band (Outband) operations.  

This guide answers the necessary pre-configuration questions chronologically and should be followed as written.

Which type of modem do I have?

The Lantronix Local Manager supports different types of cellular modems, with two major hardware distinctions (TDMA, CDMA) and two main service providers (AT&T, Verizon).

Your modem should be clearly labeled both on the packaging and the modem itself.

HSPA+, 1XRTT, GPRS Modem - 1 Antenna

HSPA Modem

LTE Modem - 2 Antennas

LTE Modem

LTE Modem

Which service provider does my modem require?

The required service provider will typically depend on the cellular technology being used (TDMA vs CDMA). Since these technologies are incompatible, you'll want to make sure you order service from the correct provider.

In the United States, the biggest providers for CDMA are Verizon and Sprint. For TDMA, you can use AT&T and T-Mobile. To determine which technology your modem is using, reference the model number on its white sticker.

HSPA+ Modems

HSPA+ modems are only available on TDMA networks, but they are certified in most countries, so you can use any service provider that supports TDMA such as AT&T and T-Mobile.

LTE Modems

AT&T LTE modems have a model number of MTSMC-LAT1-U.

Verizon CDMA modems have a model number of MTSMC-LVW2-U.

European modems have a model number of MTSMC-LEU1-U.

What kind of service plan should I order?

For most setups, you'll want to purchase a data plan with at least 15MB of data per month. Generally, service plans will allow you to pool the data usage among multiple SIM cards.

Although the Local Manager will not be using the OOB connection all the time, you should consider the typical bandwidth usage of the heartbeat service.

  • Minimal Heartbeat: 4KB approximately every 30 seconds, or 480KB/hr
  • Full Heartbeat: approximately 10KB every 30 seconds, or 1.2MB/hr
  • CLI Interaction: variable low
  • WAN Traffic Failover: variable high, tested as high as 50mbit/s

If you want to use SMS-initiated PPP, you will need both a voice and data plan.

How should I provision my SIM card?

Lantronix LTE modems require a SIM card provisioned from an LTE carrier. The SIM card can be provisioned several ways based on flexibility, geographic location, protocol and security. Here is a summary of options (easiest to most secure) to begin the selection process:

  • Direct internet SSH - The SIM should be provisioned with a static IP address that is world-routable. The provider should provision the SIM for inbound SSH on port 22 (or the port your company has chosen for these protocols).

  • Dedicated APN - If a private APN that will restrict usage to an approved list of SIM ICCIDs is configured, the SIM addressing can be public OR private and has options to attach to customer MPLS or VPN. Cost is usually a one time fee of $500-$2000 USD.

  • Reverse SSH - The SIM should be provisioned for static IP address OR dynamic addressing with a carrier NAT address. TCP port 8443 and 2222 (or the ports your company has chosen for these protocols) should be exposed from the CC's configured DNS or IP address so that a reverse SSH tunnel can be formed and used to connect end users. The management IP or DNS address the Local Manager uses for TLS (Heartbeat) must be resolve-able externally.

  • IPSEC Remote Access VPN - The SIM should be provisioned for static IP address OR dynamic addressing with a carrier NAT address. After the IP layer is established an IKEv2 IPSEC VPN is applied to force all traffic to the VPN endpoint, usually on the Customer DMZ. Lantronix has reference designs for Cisco ASA and IOS VPNs for this purpose.

What is an APN anyway?

An Access Point Name (APN) is the name of a gateway between the cellular network and another private or public network, for example, a VPN or the public Internet. It is required to get data from the Local Manager back to the Control Center or User.

It will also be required later in the Local Manager configuration as part of the modem's initialization string.

How do I install the SIM card?

An improperly installed SIM card will prevent the modem from working, so make sure it is installed correctly before installing the modem in the Local Manager.

Cellular modems require a mini-SIM (2FF) size SIM card. See for more information on SIM card sizes.

To install the SIM card, follow the white marking around the SIM card slot on the modem.


Modem cards are not hot-swappable. Shut down the Lantronix 5000 using the front panel or with the shutdown command from the system resource. For an Lantronix 500, use the shutdown command from the CLI.

LTE Modem

Note the notched corner on the upper left side of the white marking. This will coincide with the notch on your SIM card. On the slot itself, you'll notice six metal contacts; we need these to make contact with the chip on the SIM card (on reverse side of card shown in Picture.

Slide the card into the slot as shown below and make sure it is secure.

LTE Modem

How do I install the modem card in the Lantronix 500/5000?

Before installing the modem card, ensure the Local Manager is powered off. You will need a small Philips screwdriver.

The instructions below apply to both the 500 and 5000 Local Managers

LTE Modem

Step 1: Remove the blank face plate from the front of the 5000 by removing the screws in the upper-right and lower-left corner.

LTE Modem

Note the gray plastic rails that will hold the modem card and ensure proper alignment with the connector in the back.

LTE Modem

Step 2: Slide the blue part of the modem card partway into the rails.

LTE Modem

**Step 3: ** Route the gray antenna wires into the free space above the card. Make sure the wires don't get trapped inside the rails or around any edges of the green riser card.

LTE Modem

**Step 4: ** Push the modem card into the slot until it stops. It should not take any extra pressure to engage the connector in the back.

LTE Modem

**Step 5: ** Attach the faceplate to the Local Manager using the two screws from Step 1.

LTE Modem

Step 6: Attach your antenna(s) to the faceplate.


The MAIN antenna connection is REQUIRED. The AUX connection is optional but recommended for optimal performance. Your antenna(s) may differ from the ones shown in the picture.

LTE Modem

You may want to wait to attach the antennas until after the Local Manager is racked and installed in its final location.

What's the best way to mount the antennas?

For best results, position the antennas at right angles and at least two feet apart.

The shipped Local Manager LTE antennas are magnetic mounts with 5db gain that provides a higher level of performance than the "internal-antenna-carrier-coverage check" (i.e. iPhone test of signal at the site). It provides a RSRQ metric which is significantly better than RSSI since it includes a "quality" score in addition to strength.

The Lantronix CAT-M1 modem provides 100k of bandwidth and only needs 1 MHZ of spectrum to operate. It is ideal for datacenter and basement locations where signal quality is a challenge.

The Lantronix CAT-3 and above modems operate at 50-100mbit but need 15 MHZ and up to acquire a connection. These modems should use both antennas to provide optimal signal quality. All antennas need a ground plane with at least a 4 sq inch metal base for the antenna to mount to.

The 5db antennas come with 3 meters of cable attached. If it is possible to run a cable from the Local Manager to an outdoor location (or perhaps an indoor one with less RF interference), a coaxial extension cable can be added to move the antenna to a location with increased signal quality. Lightwave Research manufactures a variety of cables to support minimal signal loss over distance. LMR 200, 400, and 600 are the most commonly utilized for LTE.

Should LTE not be available, Lantronix provides an outdoor, roof-mounted satellite solution with an Iridium wireless modem. It can be cabled up to 500 feet over CAT5.

What do I next?

Now that you've purchased and activated a SIM card, installed the SIM card, and installed the modem card, you're now ready to proceed with the software configuration of the Local Manager.