Issue:
How to monitor Cisco Cellular LTE 4G backup Session when used as a backup link (ie. only becomes active when Primary link fails)?
I will detail the minimal solution to capture all scenarios to make sure your cellular backup will work when required.
- Alert when router is running on Cellular Backup?
- Alert when Cellular backup has no Service?
- Alert when Cellular Module is offline?
Background
Cisco Cellular modules either internal or modular usually run with Interface up up even though the session is not active. This doesn’t help alerting on cellular interfaces as there is no way to tell if Session is active or not by the interface status.
Some primary link interfaces also do not go into down down state to indicate an outage on Primary interface, so this also doesn’t help capturing there is an issue with primary link.
Ideally alerting on protocol is down (like BGP) on a primary link is a better option, but some WAN interfaces are running static routing which again rules out protocol alerts to indicate an issue with Primary link in all scenarios.
To avoid duplicate alerts for the same issue (ie, interface down, Protocol down) as well as the new alerts I will explain below I turned off interface and protocol alerting for any router running a Primary link and a Cellular backup.
Alert when router is running on cellular backup
Set up a custom poller to poll results from OID below. This has 3 responses as per table. We want to know when the Cellular Session becomes Active indicating that the primary link is down, router is up and running on backup connection. If the router is powered down then SolarWinds or your alerting system will have device as offline
| Name | OID | RESULTS |
| c3gGsmPacketSessionStatus | 1.3.6.1.4.1.9.9.661.1.3.3.2.1.1 | unknown(1) Active(2) Inactive(3) |
Set up an alert trigger to alert when: Node is up and the response is Active(2) for more than 5 mins.
Alert when Cellular backup has no service
The next 2 sections will make sure the Cellular backup is in the best state to make sure it will work when required.
Set up customer poller for OID below to capture if the module can see a valid service. So this will cover the scenarios where the Sim card is not inserted or become dislodged, Sim card has been disconnected by the carrier or just no signal in location to get service.
| Name | OID | RESULTS |
| c3gGsmCurrentServiceStatus | 1.3.6.1.4.1.9.9.661.1.3.2.1.2 | unknown(1) noService(2) normal(3) emergencyOnly(4) |
Set Alert Trigger to alert when: Node is up and the response is not equal to normal(3) for more than 5 minutes
Alert when cellular module is offline
Like above to capture when the whole Cellular module is offline state. Might require a reload of the module, check out earlier post on how to reboot Cellular Module without rebooting the router.
Set up a customer poller for OID below to capture if Module is in offline state.
| Name | OID | RESULTS |
| c3gModemStatus | 1.3.6.1.4.1.9.9.661.1.3.1.1.6 | unknown(1) offLine(2) onLine(3) lowPowerMode(4) |
Set Alert Trigger to alert when: Node is up and response is not equal to OnLine(3) for more than 5 minutes