Using Redundant / Dual SIM Slots


Some models of the Peplink Balance and Pepwave MAX routers contain redundant SIM slots for each embedded 4G LTE/3G modem. These SIM slots provide redundancy and data overage protection. Both SIM slots can be filled, though the Balance/MAX uses only one at a time for each modem.

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For example, the MAX HD2 Mini has 2 cellular modems. Each cellular modem has an active and a redundant SIM slot. That is, the Cellular 1 modem can choose between connecting to Carrier A or Carrier B, and likewise the Cellular 2 modem can choose between Carrier C or Carrier D.


Here are two scenarios in which taking advantage of both SIM slots can result in greater reliability and cost savings:

  1. Installing SIMs from two carriers If the signal from one carrier fails, the device can automatically connect to an alternate carrier using the second installed SIM.
  2. Installing two SIMs with independent monthly data allowances. If the cellular account associated with one installed SIM reaches its data allowance, the device can automatically switch to a second installed SIM associated with a separate data plan, helping you avoid expensive data overages.

Redundant SIM card prioritization

With two SIM cards inserted, you can choose whether to use SIM card A or SIM card B, or both.
First, head to WAN Connections and click Details on your Cellular WAN connection

For the purpose of this article, we will go ahead and enable both SIMs.

It’s also possible to pick a preferred SIM card so that you can prioritize which gets used first, and the conditions for which the router falls back onto the preferred SIM card.

Controlling cellular data usage

You can use the built-in bandwidth allowance monitor to control the amount of cellular data used to help prevent data overage charges.

To do so, under Cellular Settings, look for Bandwidth Allowance Monitor and then tick the Enable check box for the chosen SIM card.

Note that data reported may differ from your network provider’s meter.

Once enabled, further options open up. The first things to set is the billing cycle date. Set the start day of each month so that the allowance counter resets and then enter cellular data you’re allowed in Monthly Allowance.

Next, you can choose what actions the router would take once the cellular data limit is reached, such as the ability to receive email notifications (if already set up previously), or to have the router stop using the selected SIM card altogether by ticking “Disconnect when usage hits 100%”.

The same can be configured for SIM B.