# Detecting Spoke Failure from Hub using System Tag

**URL:** <https://forum.inductiveautomation.com/t/detecting-spoke-failure-from-hub-using-system-tag/41527>\
**Category:** Ignition\
**Tags:** ignition80\
**Created:** [December 15, 2020, 3:32pm UTC](https://forum.inductiveautomation.com/t/detecting-spoke-failure-from-hub-using-system-tag/41527 "2020-12-15T15:32:05Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![prashanta.shrestha](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/prashanta.shrestha/32/20575_2.png) [@prashanta.shrestha](https://forum.inductiveautomation.com/u/prashanta.shrestha)\
**Post date:** [December 15, 2020, 3:32pm UTC](https://forum.inductiveautomation.com/t/detecting-spoke-failure-from-hub-using-system-tag/41527/1 "2020-12-15T15:32:05Z")

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Hub Ignition Version: 8.0.15 (64-bit) (Running in Azure Ubuntu VM)  
Spoke Ignition Version: 8.1.1 (64-bit) (Running in Docker)

Trying to implement an alarm notification on Hub when there is no communication from Spoke. Particularly interested in utilizing IsAvailable System Tag:

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/2/7/278107ec9baf56f8f074977c4cc1075da639268d.png)

I have an alarm setup to send notification when IsAvailable tag transitions to false.

Here are the tests done to generate the alarm:

**1. Shutting down Spoke Ignition Gateway (worked as expected)**

Spoke Ignition Gateway was shutdown (stopped the docker container), the alarm was triggered and worked as expected.

**2. Disrupt network connection between Hub and Spoke (Did not work as expected)**

When connection was disrupted between Hub and Spoke either by disconnecting VPN connection or by blocking port 8060 to Hub - spoke gateway logs show web socket errors but the alarm never gets triggered.

Any thoughts on this and how to utilize IsAvailable Tag?

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**Author:** ![JordanCClark](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jordancclark/32/83362_2.png) [@JordanCClark](https://forum.inductiveautomation.com/u/JordanCClark)\
**Post date:** [December 15, 2020, 5:28pm UTC](https://forum.inductiveautomation.com/t/detecting-spoke-failure-from-hub-using-system-tag/41527/2 "2020-12-15T17:28:44Z")

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Does the LastComm tag update when it’s disrupted? Monitoring that may be more effective.

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**Author:** ![prashanta.shrestha](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/prashanta.shrestha/32/20575_2.png) [@prashanta.shrestha](https://forum.inductiveautomation.com/u/prashanta.shrestha)\
**Post date:** [January 10, 2021, 4:22pm UTC](https://forum.inductiveautomation.com/t/detecting-spoke-failure-from-hub-using-system-tag/41527/3 "2021-01-10T16:22:43Z")

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It seems like the IsAvailable System Tag is working, it takes about 12 mins for the Hub to mark the Spoke Ignition as unavailable after the fact. I ended up using Spoke’s system uptime tag as a derived tag on Hub to generate the alarm on stale tag value.