ACI Fabric Policies Monitoring Common Policy vs default?

[SIMMN]

First of all, I have been design and implementing ACI for a number of years now and I still find the overall monitoring setup is totally confusing within APIC...

I have this simple question: Under Fabric -> Fabric Policies -> Policies -> Monitoring, there are two sub-menus: Common Policy and default... What are the difference between the two and when to use each for monitoring configuration?

According to help guide, the Common Policy is the monitoring policy model for the common semantic scope, which is used when there is no corresponding policy under the more specific infra or tenant scopes. In such cases, these policies are used throughout the fabric except for objects attached to their own specific policies. 

But honestly, this sounds like what the default is supposed to be for me...

Any advices?

[Robert Burns · Accepted solution]

There are three heirarchies you can apply policies to in ACI: Access Policies, Fabric Policies & Tenant Policies.  

Within each of these heirachies (Access, Fabric, Tenant) there is a default monitoring policy which as you know contains the initial values for any policies created within that respective heirarchy.   This would be used if/when you wanted to create a monitoring policy for ONLY Access Policies OR Fabric Policies OR Tenant level.

If instead you want a fabric-wide monitoring policy, that applies across ALL heirarchies, this is where the "Common" monitoring policies comes in.  Think of this askin to the "common" tenant logic, but applies for monitoring policies across the entire fabric (access/fabric policies & tenant)

• Fabric Wide: includes both fabric and access objects   <<< Fabric Policies - Monitoring - Common Policy
  monCommonPol (uni/fabric/moncommon): applies to all fabric, access, and tenant hierarchies

• Access (also known as infrastructure): access ports, FEX, VM controllers, and so on  <<< Access Policies - Monitoring - default
monFabricPol(uni/fabric/monfab-default): applies to fabric hierarchies
  

• Fabric: fabric ports, cards, chassis, fans, and so on <<< Fabric Policies - Monitoring - default
monInfraPol (uni/infra/monifra-default): applies to the access infrastructure hierarchy

• Tenant: EPGs, application profiles, services, and so on <<< TenantX - Monitoring - default
  monEPGPol (uni/tn-common/monepg-default): applies to tenant hierarchies
  
  Hope this helps,
  Robert

[SIMMN]

Thanks @Robert Burns! Appreciated! Wish all ACI documents are this easy to read

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