Troubleshoot Common Cellular Interface Issues | Troubleshooting Tools and Methods | Cisco Catalyst SD-WAN Troubleshooting Guide

This topic describes the most common issues and error messages that occur with cellular connections from the router to the cellular network, and the steps to resolve them.

Insufficient Radio Signal Strength

Problem statement: The cellular module in the router cannot detect a radio signal from the service provider network.

Identify the problem: The signal strength displayed in the Cisco SD-WAN Manager Cellular Status screen or with the show cellular status CLI command, or in the Cellular Radio screen or with the show cellular radio command is no signal, poor, or good. It should be excellent. The following table lists the ranges of signal strengths:

Table 1.
Signal	Excellent	Good	Fair	Poor
Received signal strength indicator (RSSI)	>= -65 dBm	-65 to -75 dBm	-75 to -85 dBm	<= -85 dBm
Reference signal receive power (RSRP)	>= -80 dBm	–80 to -90 dBm	–90 to -100 dBm	<= -100 dBm
Reference signal receive quality (RSRQ)	>= -10 dBm	-10 to -15 dB	-15 to -20 dB	< –20 dB
Signal-to-noise ratio (SNR)	>= 20 dB	13 to 20 dB	0 to 13 dB	<= 0 dB

Note

All parameters must be considered together and not in isolation. For example, a strong RSSI does not mean signal quality is good if RSRP is bad.

The wireless LED on the router is lit (solid or blinking) and is red, orange or yellow, or it is blinking green. It should be solid green.

Resolve the Problem

Examine the router to verify that both basic antennas are correctly installed.
Contact the service provider to verify that the location has coverage.
Move the router to a new location within the building.
Procure an additional external cabled antenna and connect it to the router.

Modem Status Remains in Low-Power Mode

Problem Statement: End users cannot connect to the cellular network, and the modem status remains in low-power mode.

Identify the Problem:

End users cannot connect to the cellular network.
The error message "Missing or unknown APN" is generated.
The signal strength is less than excellent.

Resolve the Problem

Verify that there is sufficient radio signal strength. If there is not, follow the instructions in the Insufficient Radio Signal Strength section.
Verify that the cellular0 interface is operational. When the cellular interface is shut down, the modem status is set to Low Power mode. To do this, from the Cisco SD-WAN Manager menu, choose Monitor > Devices .

Cisco vManage Release 20.6.1 and earlier: To do this, from the Cisco SD-WAN Manager menu, choose Monitor > Network .

Then click Real Time , and from the Device Options drop-down list, choose Interface Detail .

To do this from the CLI, use the show interface command. Check that the Admin Status and Oper Status values are both Up.
Verify that the modem temperature is not above or below the threshold temperatures. To view the modem temperature, from the Cisco SD-WAN Manager menu, choose Monitor > Devices and select the router.

Cisco vManage Release 20.6.1 and earlier: To do this, from the Cisco SD-WAN Manager menu, choose Monitor > Network .

Then click Real Time , and from the Device Options drop-down list, choose Cellular Modem .

From the CLI, use the show cellular modem command.
Check that the access point name (APN) in the profile for the cellular0 interface matches the name expected by your service provider. Some service provides required that you configure the APN, and they include configuration instructions in the SIM card package.
1. To check which APN name is configured, from the Cisco SD-WAN Manager menu, choose Monitor > Devices and select the router.
  
  Cisco vManage Release 20.6.1 and earlier: To do this, from the Cisco SD-WAN Manager menu, choose Monitor > Network .
  
  Then click Real Time , and from the Device Options drop-down list, choose Cellular Profiles .
  
  From the CLI, use the show cellular profiles command. The APN column shows the name of the APN. Each profile specifies an access point name (APN), which is used by the service provider to determine the correct IP address and connect to the correct secure gateway. For some profiles, you must configure the APN.
2. If the APN is not the one required by the service provider, configure the correct APN. From the Cisco SD-WAN Manager menu, choose Configuration > Templates and use the Cellular Profile feature template.
  
  To configure this from the CLI, use the cellular cellular0 profile apn command.
If none of the previous steps works, reset the cellular interface.

Error Messages

The following table list the most common error messages that are displayed regarding cellular interfaces:

Table 2.
Error Message	Problem Statement	How Do I Fix the Problem
Authentication failed	End user authentication failed, because the service provider cannot authenticate either the user's SIM card or the edge device SIM card.	Contact the cellular service provider.
Illegal MS	The service provider denied access to an end user, because the end user is blocked from the network.	Contact the cellular service provider.
Operator has barred the UE	The service provider denied access to an end user, because the end user failed the authentication check.	Contact the cellular service provider.
MS has no subscription for this service	The service provided denied access to an end user, because the operator has barred the end user.	Contact the cellular service provider.
Illegal ME	The service provided denied access to an end user, because the end user has no subscription.	Contact the cellular service provider.
Insufficient resources	The service provider network is experiencing congestion because of insufficient resources and cannot provide the requested service to an end user.	The device automatically tries to reconnect. (The duration between retries depends on the service provider.) If the issue does not resolve itself, contact the cellular service provider.
IPV4 data call throttled	The SIM card being used in the device requires that you configure static APN.	Verify whether the data plan associated with the SIM card requires a static APN. If so, change the APN to the name specified the SIM card instructions, as described in Modem Status Remains in Low-Power Mode , above.
Missing or unknown APN	End users cannot connect to the cellular network, either because an APN is required and is not included in the cellular profile or because the APN could not be resolved by the service provider.	See the profile's APN, as described in Modem Status Remains in Low-Power Mode , above.
Network failure	The service provider network is experiencing difficulties.	The device automatically tries to reconnect. (The duration between retries depends on the service provider.) If the issue does not resolve itself, contact the cellular service provider.
Network is temporarily out of resources	The service provider network is experiencing congestion because of insufficient resources and cannot provide the requested service to an end user.	The edge device automatically tries to reconnect. (The duration between retries depends on the service provider.) If the issue does not resolve itself, contact the cellular service provider.
Requested service option not subscribed	The SIM card being used in the edge device requires that you configure a static APN entry.	Verify whether the data plan associated with the SIM card requires a static APN. If so, change the APN to the name specified the SIM card instructions, as described in Modem Status Remains in Low-Power Mode , above.
Service not supported by the PLMN	The Public Land Mobile Network (PLMN) does not support data service.	Contact the cellular service provider.