Configure SureLink active recovery to detect modem failures

Problems can occur beyond the immediate modem connection that prevent some IP traffic from reaching its destination. Normally this kind of problem does not cause the IX14 device to detect that the modem has failed, because the connection continues to work while the core problem exists somewhere else in the network.

Using Digi SureLink, you can configure the IX14 device to regularly probe connections through the modem to determine if the modem connection has failed.

Required configuration items

Enable SureLink.
SureLink can be enabled for both IPv4 and IPv6 configurations. By default, SureLink is enabled for IPv4 for the preconfigured Modem interface. It is disabled for IPv6.
When SureLink is configured for Wireless WANs, SureLink tests are only run if the cellular modem is connected and has an IP address. Use the SIM failover options to configure the IX14 device to automatically recover the modem in the event that it cannot obtain an IP address. See Configure a Wireless Wide Area Network (WWAN) for details about SIM failover.
The type of probe test to be performed, one of:
- Test another interface's status: Used to create a failover or coupled relationship between two interfaces. Requires the name of the alternate interface, the IP version to be tested, and the expected status of the alternate interface (either up or down).
- Ping: Requires the hostname or IP address of the host to be pinged.
- DNS query: You can perform a DNS query to a named DNS server, or to the DNS servers configured for the WAN.
- HTTP test: Requires the URL of the host to be tested.
- Test DNS servers configured for this interface: Tests communication with this interface's DNS servers that are either provided by DHCP, or statically configured.
- Interface status: Determines if the interface has an IP address assigned to it, that the physical link is up, and that a route is present to send traffic out of the network interface.
The preconfigured Modem interface is configured by default to use SureLink to both test the interface status and perform a test DNS query.

Additional configuration items

The behavior of the IX14 device upon test failure:
- The default behavior, which is to restart the Modem interface.
- SIM switching (also enabled by default).
- Reset the modem.
- Reboot the device.
The interval between connectivity tests.
The number of probe attempts before the Modem interface is considered to have failed.
The amount of time that the device should wait for a response to a probe attempt before considering it to have failed.
If the type of probe test is:
- Ping: Configure the number of bytes in the ping packet.
- Interface status: Configure the amount of time that the interface is down before it is considered to have failed, and the amount of time it takes to make an initial connection before it is considered down.
Additional test targets.
If more than one test target is configured, determine whether the interface should fail over based on the failure of one of the test targets, or all of the test targets.

Order of precedence for SureLink actions

If multiple SureLink actions, such as restarting the interface and rebooting the device, are enabled, the following order of precedence is used:

Restart interface
Switch to the alternate SIM
Reset the modem
Reboot the device

For example, if SureLink is configured as follows:

Restart interface:
- Enabled
- Restart fail count: 2
Reset modem:
- Enabled
- Reset mode fail count: 3
Switch SIM:
- Enabled
- Switch SIM fail count: 5
Reboot device:
- Enabled
- Reboot fail count: 7

SureLink will: The device will:

First SureLink failure: Nothing will happen.
Second SureLink failure: The interface will restart.
Third SureLink failure: The modem will reset.
Fourth SureLink failure: The interface will restart again.
Fifth SureLink failure: The device will switch to the alternate SIM.

Note The Switch SIM behavior only applies if the modem is connected, but SureLink tests are failing. If the modem is not connected, SIM failover applies. See Configure a Wireless Wide Area Network (WWAN) for more information about the SIM failover option.
Sixth SureLink failure: The interface will restart again.
Seventh Surelink failure: The device will reboot.

To configure the IX14 device to regularly probe connections through the WWAN:

 Web

SureLink can be configured for both IPv4 and IPv6.

Log into Digi Remote Manager, or log into the local Web UI as a user with full Admin access rights.
Access the device configuration:
Remote Manager:
1. Locate your device as described in Use Digi Remote Manager to view and manage your device.
2. Click the Device ID.
3. Click Settings.
4. Click to expand Config.
Web UI:
1. On the menu, click System. Under Configuration, click Device Configuration.
  The Configuration window is displayed.
Click Network > Interfaces.
Create a new WWAN or select an existing one:
- To create a new WWAN, see Configure a Wireless Wide Area Network (WWAN).
- To edit an existing WWAN, click to expand the appropriate WWAN.
After creating or selecting the WWAN, click IPv4 (or IPv6) > SureLink.
Enable SureLink.

SureLink can be enabled for both IPv4 and IPv6 configurations. By default, SureLink is enabled for IPv4 for the preconfigured WWAN (Modem). It is disabled for IPv6.

Restart interface is enabled by default.
- (Optional) For Restart fail count, type or select the number of times that the Surelink test must fail before the interface is restarted. The default is 1.
(Optional) Reset modem is enabled by default. To disable, toggle off Enable.
- (Optional) For Reset modem fail count, type or select the number of times that the Surelink test must fail before the modem is reset. The default is 3.
Switch SIM is enabled by default. Click to disable.
- If Switch SIM is enabled, for Switch SIM fail count, type or select the number of times that the Surelink test must fail before the modem switches to the alternate SIM. The default is 5.
Note The SureLink Switch SIM option differs from the SIM failover option, which is set during WWAN configuration. SIM failover applies when the modem is unable to connect to a cellular network, whereas Switch SIM applies when the WWAN interface is failing SureLink tests even though the modem is connected. See Configure a Wireless Wide Area Network (WWAN) for more information about the SIM failover option.
(Optional) Enable Reboot device.
If Reboot device is enabled at the same time as either Restart interface or Reset modem, Reboot device takes precedence.
- For Reboot fail count, type or select the number of times that the Surelink test must fail before the device is rebooted. The default is 1.
Click to expand Test targets.
For Add Test Target, click .
Select the Test type:
- Test another interface's status: Allows you to test another interface's status, to create a failover or coupled relationship between interfaces. If Test another interface's status is selected:
  - For Test Interface, select the alternate interface to be tested.
  - For IP version, select the alternate interface's IP version. This allows you to determine the alternate interface's status for a particular IP version.
  - For Expected status, select whether the expected status of the alternate interface is Up or Down. For example, if Expected status is set to Down, but the alternate interface is determined to be up, then this test will fail.
- Ping test: Tests connectivity by sending an ICMP echo request to the hostname or IP address specified in Ping host. You can also optionally change the number of bytes in the Ping payload size.
- DNS test: Tests connectivity by sending a DNS query to the specified DNS server.
- HTTP test: Tests connectivity by sending an HTTP or HTTPS GET request to the URL specified in Web servers. The URL should take the format of http[s]://hostname/[path].
- Test DNS servers configured for this interface: Tests connectivity by sending a DNS query to the DNS servers configured for this interface.
- Test the interface status: The interface is considered to be down based on:
  - Down time: The amount of time that the interface can be down before this test is considered to have failed.
    Allowed values are any number of weeks, days, hours, minutes, or seconds, and take the format number{w|d|h|m|s}.
    For example, to set Down time to ten minutes, enter 10m or 600s.
    The default is 60 seconds.
  - Initial connection time: The amount of time to wait for an initial connection to the interface before this test is considered to have failed.
    Allowed values are any number of weeks, days, hours, minutes, or seconds, and take the format number{w|d|h|m|s}.
    For example, to set Initial connection time to ten minutes, enter 10m or 600s.
    The default is 60 seconds.
Optional active recovery configuration parameters:
1. Change the Interval between connectivity tests.
  Allowed values are any number of weeks, days, hours, minutes, or seconds, and take the format number{w|d|h|m|s}.
  For example, to set Interval to ten minutes, enter 10m or 600s.
  The default is 15 minutes.
2. If more than one test target is configured, for Success condition, determine whether the interface should fail over based on the failure of one of the test targets, or all of the test targets.
3. For Pass threshold, type or select the number of times that the test must pass after failure, before the interface is determined to be working and is reinstated.
4. For Failed attempts, type the number of probe attempts before the WAN is considered to have failed.
5. For Response timeout, type the amount of time that the device should wait for a response to a probe attempt before considering it to have failed.
  Allowed values are any number of weeks, days, hours, minutes, or seconds, and take the format number{w|d|h|m|s}.
  For example, to set Response timeout to ten minutes, enter 10m or 600s.
  The default is 15 seconds.
(Optional) Repeat this procedure for IPv6.
Click Apply to save the configuration and apply the change.

 Command line

Active recovery can be configured for both IPv4 and IPv6. These instructions are for IPv4; to configure IPv6 active recovery, replace ipv4 in the command line with ipv6.

Select the device in Remote Manager and click Actions > Open Console, or log into the IX14 local command line as a user with full Admin access rights.
Depending on your device configuration, you may be presented with an Access selection menu. Type admin to access the Admin CLI.
At the command line, type config to enter configuration mode:
```
> config
(config)>
```
Create a new WWAN, or edit an existing one:
- To create a new WWAN, see Configure a Wireless Wide Area Network (WWAN).
- To edit an existing WWAN, change to the WWAN's node in the configuration schema. For example, for a WWAN named my_wwan, change to the my_wwan node in the configuration schema:
```
(config)> network interface my_wwan
(config network interface my_wwan)>
```
Enable SureLink.
SureLink can be enabled for both IPv4 and IPv6 configurations. By default, SureLink is enabled for IPv4 for the preconfigured WWAN (modem). It is disabled for IPv6.
```
(config network interface my_wwan> ipv4 surelink enable true
(config network interface my_wwan)>
```
By default, the device is configured to restart the interface when its connection is considered to have failed.
To disable:
```
(config network interface my_wwan ipv4 surelink)> restart false
(config network interface my_wwan ipv4 surelink> 
```
- (Optional) Set the number of times that the Surelink test must fail before the interface is restarted:
```
(config network interface my_wwan ipv4 surelink)> restart_attempts int
(config network interface my_wwan ipv4 surelink> 
```
  where int is any number greater than 0. The default is 1.
(Optional) By default, the device is configured to reset the modem when its connection is considered to have failed.
To disable:
```
(config network interface my_wwan ipv4 surelink)> reset_modem false
(config network interface my_wwan ipv4 surelink> 
```
- If reset_modem is enabled, set the number of times that Surelink tests must fail prior to resetting the modem:
```
(config network interface my_wwan ipv4 surelink)> reset_modem_attempts int
(config network interface my_wwan ipv4 surelink> 
```
  where int is an integer between 1 through 5. The default is 3.
SIM switching is enabled by default. To disable:
```
(config network interface my_wwan ipv4 surelink)> switch_sim false
(config network interface my_wwan ipv4 surelink> 
```
Note The SureLink switch_sim option differs from the sim_failover option, which is set during WWAN configuration. sim_failover applies when the modem is unable to connect to a cellular network, whereas switch_sim applies when the WWAN interface is failing SureLink tests even though the modem is connected. See Configure a Wireless Wide Area Network (WWAN) for more information about the sim_failover option.

If switch_sim is enabled, set the number of times that Surelink tests must fail prior to switching SIMS:
```
(config network interface my_wwan ipv4 surelink)> switch_sim_attempts int
(config network interface my_wwan ipv4 surelink> 
```
where int is an integer between 1 through 5. The default is 5.

(Optional) Set the device to reboot when the interface is considered to have failed:
```
(config network interface my_wwan ipv4 surelink)> reboot true
(config network interface my_wwan ipv4 surelink> 
```
Note If the reboot parameter is enabled at the same time as either the restart or reset_modem parameters, the reboot parameter takes precedence.
- (Optional) Set the number of times that the Surelink test must fail before the device is rebooted:
```
(config network interface my_wwan ipv4 surelink)> reboot_attempts int
(config network interface my_wwan ipv4 surelink> 
```
  where int is any number greater than 0. The default is 1.

Add a test target:

(config network interface my_wwan)> add ipv4 surelink target end
(config network interface my_wwan ipv4 surelink target 0)>

Set the test type:

(config network interface my_wwan ipv4 surelink target 0)> test value
(config network interface my_wwan ipv4 surelink target 0)>

where value is one of:

ping: Tests connectivity by sending an ICMP echo request to a specified hostname or IP address.

Specify the hostname or IP address:

(config network interface my_wwan ipv4 surelink target 0)> ping_host host
(config network interface my_wwan ipv4 surelink target 0)>

(Optional) Set the size, in bytes, of the ping packet:

(config network interface my_wwan ipv4 surelink target 0)> ping_size [num]
(config network interface my_wwan ipv4 surelink target 0)>

dns: Tests connectivity by sending a DNS query to the specified DNS server.
- Specify the DNS server. Allowed value is the IP address of the DNS server.
```
(config network interface my_wwan ipv4 surelink target 0)> dns_server ip_address
(config network interface my_wwan ipv4 surelink target 0)>
```
dns_configured: Tests connectivity by sending a DNS query to the DNS servers configured for this interface.
http: Tests connectivity by sending an HTTP or HTTPS GET request to the specified URL.
- Specify the url:
```
(config network interface my_wwan ipv4 surelink target 0)> http_url value
(config network interface my_wwan ipv4 surelink target 0)> 
```
  where value uses the format http[s]://hostname/[path]

interface_up: The interface is considered to be down based on the interfaces down time, and the amount of time an initial connection to the interface takes before this test is considered to have failed.

(Optional) Set the amount of time that the interface can be down before this test is considered to have failed:

(config network interface my_wwan ipv4 surelink target 0)> interface_down_time value
(config network interface my_wwan ipv4 surelink target 0)>

The default is 60 seconds.

(Optional) Set the amount of time to wait for an initial connection to the interface before this test is considered to have failed:
```
(config network interface my_wwan ipv4 surelink target 0)> interface_timeout value
(config network interface my_wwan ipv4 surelink target 0)> 
```
The default is 60 seconds.

other: Allows you to test another interface's status, to create a failover or coupled relationship between interfaces:

(config network interface my_wwan ipv4 surelink target 0)> other value
(config network interface my_wwan ipv4 surelink target 0)>

If other is set:

Set the alternate interface to be tested:

Set the interface. For example:

(config network interface my_wan ipv4 surelink target 0)> other_interface /network/interface/lan
(config network interface my_wan ipv4 surelink target 0)>

Set the alternate interface's IP version. This allows you to determine the alternate interface's status for a particular IP version.
```
(config network interface my_wwan ipv4 surelink target 0)> other_ip_version value
(config network interface my_wwan ipv4 surelink target 0)> 
```
where value is one of: any, both, ipv4, or ipv6.
Set the expected status of the alternate interface:
```
(config network interface my_wwan ipv4 surelink target 0)> other_status value
(config network interface my_wwan ipv4 surelink target 0)> 
```
where value is either up or down. For example, if other_status is set to down, but the alternate interface is determined to be up, then this test will fail.

(Optional) Repeat to add additional test targets.

Optional active recovery configuration parameters:
1. Move back two levels in the configuration by typing .. ..:
```
(config network interface my_wwan ipv4 surelink target 0)> .. ..
(config network interface my_wwan ipv4 surelink> 
```
2. Set the Interval between connectivity tests:
```
(config network interface my_wwan ipv4 surelink)> interval value
(config network interface my_wwan ipv4 surelink> 
```
  The default is 15 minutes.
3. If more than one test target is configured, determine whether the interface should fail over based on the failure of one of the test targets, or all of the test targets:
```
(config network interface my_wwan ipv4 surelink)> success_condition value
(config network interface my_wwan ipv4 surelink> 
```
  Where value is either one or all.
4. Set the number of probe attempts before the WAN is considered to have failed:
```
(config network interface my_wwan ipv4 surelink)> attempts num
(config network interface my_wwan ipv4 surelink> 
```
  The default is 3.
5. Set the amount of time that the device should wait for a response to a probe attempt before considering it to have failed:
```
(config network interface my_wwan ipv4 surelink)> timeout value
(config network interface my_wwan ipv4 surelink> 
```
  The default is 15 seconds.
(Optional) Repeat this procedure for IPv6.

Save the configuration and apply the change:

(config network interface my_wwan ipv4 surelink)> save
Configuration saved.
>

Type exit to exit the Admin CLI.
Depending on your device configuration, you may be presented with an Access selection menu. Type quit to disconnect from the device.