Complete Guide: Configuring 5G Enterprise WAN Failover on Teltonika RUTX50 with Dual SIM

Introduction to Enterprise WAN Redundancy on the RUTX50

In modern enterprise environments, uninterrupted network connectivity is non-negotiable. The Teltonika RUTX50, with its 5G capabilities and dual SIM slots, provides a robust platform for building highly available WAN solutions. The core feature enabling this resilience is Failover. This function allows the router to maintain a primary WAN connection (e.g., SIM 1) and automatically switch to a secondary, or backup, connection (e.g., SIM 2 or a wired WAN) in the event the primary link fails.

The failover logic is governed by a simple yet effective priority system based on interface metrics. As per Teltonika's official documentation, interfaces with a higher metric value are given higher priority. The RUTX50 will exclusively use the highest-metric, active interface for all traffic. Should this interface go offline, the router seamlessly transitions to the interface with the next-highest metric. This mechanism is distinct from Load Balancing, which distributes traffic across multiple WANs simultaneously. It is critical to note that Failover and Load Balancing cannot be used at the same time.

Prerequisites

• A Teltonika RUTX50 router with administrative access to the WebUI.
• Firmware version RUTX_R_00.07.24.2 or a more recent release.
• At least two active WAN sources. For this guide, we assume two active 5G/4G SIM cards from different carriers inserted into the router. The same principles apply to a SIM and a wired WAN configuration.
• The Failover package must be installed. Verify this under System → Package Manager. If it is not listed, find and install it from the available packages list.

Step-by-Step Configuration for Dual SIM Failover

This guide details the process of configuring the RUTX50 to use a primary SIM card and automatically fail over to a secondary SIM card upon connection loss.

1. Navigate to the Failover Menu

   Log in to your RUTX50's WebUI. In the main navigation menu, go to Network → Failover. This is the central hub for managing all WAN redundancy settings.

2. Set Interface Priorities (Metrics)

   In the Interfaces section, you will see a list of all potential WAN interfaces (e.g., Mobile, Wired WAN). Your two mobile SIM interfaces will be listed here. To establish a primary/backup relationship:

   • Identify your primary SIM interface (e.g., mob1s1a1). Set its Metric to a high value, such as 100.
   • Identify your secondary SIM interface (e.g., mob1s2a1). Set its Metric to a lower value, such as 90.

   With this configuration, the router will always prefer the interface with metric 100. It will only use the interface with metric 90 if the primary is determined to be offline. Click Save & Apply.

   Note: The exact interface names for your SIMs may vary. They typically follow a pattern like mob[modem_number]s[sim_slot]a[apn_profile].

3. Configure Primary Interface Health Checks

   The router needs a reliable method to determine if an interface is "offline". This is achieved through active health checks. In the Interfaces list, find your primary SIM interface (the one with metric 100) and click the Edit button next to it.

   Configure the following parameters based on the official documentation:

   • Enable: Set to on.
   • Method: Select Ping. This is the most common and reliable method.
   • Track IP: Enter at least two highly-available public IP addresses, separated by commas. For example: 1.1.1.1,8.8.8.8. The interface will be considered offline if it cannot reach any of these hosts.
   • Reliability: Set to 1. This means the test is successful if at least one of the tracked IPs responds.
   • Count: Set to 1. This is the number of pings sent to each host per test interval.
   • Down: Set to 3. This is a critical value; it defines the number of consecutive failed tests required to mark the interface as 'Offline' and trigger the failover.
   • Up: Set to 3. This defines the number of consecutive successful tests required to mark a previously offline interface as 'Online', triggering a failback to the primary connection.
   • Interval: Set to 3 (seconds). This is the time between each health check test.

   Click Save & Apply. Your primary interface is now being actively monitored.

4. Configure Secondary Interface Health Checks

   Repeat the exact same health check configuration for your secondary SIM interface (the one with metric 90). This is important so the router knows if the backup link is viable before and during a failover event. Click Save & Apply.

5. Verify Policy and Rule Configuration

   Navigate to the Rule tab within the Failover menu. By default, there is a rule named default. Click Edit to inspect it.

   • Destination address: Should be 0.0.0.0/0 to match all outbound traffic.
   • Policy: Should be set to default (Failover).

   This default rule ensures that all traffic from your LAN is subject to the failover logic you configured. For most enterprise scenarios, this default rule is sufficient and requires no changes.

Interface Health Check Parameter Reference

Fine-tuning these parameters is key to balancing rapid failover with stability. A more aggressive configuration (lower `Interval` and `Down` values) will fail over faster but may be susceptible to false positives from transient network flaps.

Frequently Asked Questions (FAQ)

What is the difference between Failover and Load Balancing on the RUTX50?

Failover is a high-availability feature that provides a backup WAN connection. It uses only one connection at a time, based on a priority (metric) system. Load Balancing is a performance feature that distributes traffic across multiple WAN connections simultaneously to increase aggregate bandwidth. They are mutually exclusive and cannot be enabled at the same time.

How quickly will the RUTX50 failover to the secondary SIM?

The failover time is a direct function of the health check parameters. The minimum time to detect an outage is calculated as Interval × Down. With the recommended settings (3 seconds × 3 retries), the router will detect a failure in approximately 9 seconds, after which it will switch to the backup interface.

Will the RUTX50 automatically switch back (failback) to the primary SIM when it's available again?

Yes. The failback mechanism is automatic and is controlled by the Up parameter in the interface health check settings. Once the primary interface passes the required number of consecutive successful tests (e.g., 3), the router will mark it as 'Online' and, because it has a higher metric, will switch all traffic back to it.

Can I use a wired WAN connection as my primary and a 5G SIM as the backup?

Absolutely. The logic is identical. Simply navigate to Network → Failover and assign a higher metric (e.g., 100) to your Wired WAN interface and a lower metric (e.g., 90) to your Mobile interface. The router will then prioritize the wired connection and use the 5G SIM only as a backup.

What IP addresses should I use for the 'Track IP' setting?

It is critical to use highly reliable and geographically diverse IP addresses that are not part of your primary ISP's network. Using your ISP's DNS servers can lead to a situation where the local link is up but the ISP's core network is down, preventing a failover. Best practice is to use public DNS resolvers like Cloudflare (1.1.1.1, 1.0.0.1), Google (8.8.8.8, 8.8.4.4), or Quad9 (9.9.9.9). Using multiple IPs increases the reliability of the health check itself.