CA Spectrum alarm for WA_Link - Three or more devices connected by WA_Segment

Products

• CA Spectrum

Issue/Introduction

We're seeing the event and alarm 0x10d57 in Spectrum:

An invalid Wide Area Segment association has been created for device <IP_ADDRESS>. The problem is Too-Many-Connections-To-WA_Segment-(>2).
THREE OR MORE DEVICES CONNECTED BY WA_SEGMENT

Symptoms:  SpectroSERVER may exhibit unpredictable behavior and instability.

Environment

Release: Any
Component: SPCAEM

Cause

The modelling scenario contains a Wide Area Link with a Wide Area Segment that is connecting more than 2 devices. Even though Spectrum allows such an association, this is not the intention of the design of the Wide Area Segment.

Resolution

Spectrum uses WA_Link models to represent a one to one (single port to single port) connection.  When you see this event/alarm, it is because the WA_Link is connected to more than 2 devices.  When the WA_Link is connected to more than 2 devices, this confuses Spectrum's internal Fault Isolation logic, and will cause undesirable alarming issues (for instance, you may not receive a proper alarm when the link goes down).  This could potentially happen in an environment running DMVPN.  Spectrum does not support DMVPN and therefore is confused when trying to model devices with many connections from the same port.  

Spectrum has two other models that are meant for a "One -> many" connection, these being:

1. The Fanout model : You can use this to replace the Wide Area Link and Wide Area Segment models. Generally it is recommended to destroy the WA_Link and use a Fanout if the modeling connectivity is needed as the Fanout model is designed for this task and will not cause instability in the SpectroSERVER.
2. The SharedMediaLink model :    If there are 25 or more connections, you should use the SharedMediaLink modeltype instead.  These will need to be manually created and connected to the devices in question. 

Additional Information

If you are unable to destroy the WA_Link due to DMVPN functionality, you can set the WA_Link fault isolation mode to Transparent which will remove the WA_Link from the fault isolation configuration.  You will still receive alarms on the connected interfaces, but not on the WA_Link itself. You can do this under;

Spectrum OneClick ->  VNM model -> Component Detail -> Fault isolation

Change the WA Link Fault Isolation Mode from Normal to Transparent.

A SpectroSERVER restart might be needed to free up the threads if it is already consumed with fault isolation WA_Links.