Cisco ACI Multi-Pod vs Multi-Site: Detailed Comparison

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Application centric architectures are core of networking which help to derive maximum value from data centre networks powered by them. Application centric architectures (ACIs) provide flexibility to leverage ACIs policy model in single data centre, multiple data centres or in public cloud environments. They let organizations expand, secure and interconnect data centres located all over the world.

Today we look more in detail about two most powerful and distinct architectures Cisco ACI Multi Pod vs Multi-site, major differences between the two, purpose for which they are deployed and use cases.

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About Cisco ACI Multi-Pod

Before we deep dive into these two distinct architectures we need to understand two terminologies commonly used or associated with them. A ‘Fabric’ is a spine leaf topology of Nexus 9000 series switches with a single cluster of application policy infrastructure controllers (APIC); it is a single point of management for ACI fabric. A ‘Pod’ is a set of interconnected ACI leaf and spine switches that are under the control of a specific APIC cluster.

ACI fabric could have multiple Pods and all these Pods are part of the same fabric and are under the control of the same APIC cluster. If you have multiple fabrics, each with its own APIC cluster then independent ACI clusters are referred to as ‘Sites’. A ‘Site’ is a single fabric in the ACI world.

The ACI multi-Pod architecture is an extension of pre-existing ACI fabric without the need to set up new fabric from the start. ACI Multi-pod fabric comprises two to twelve ACI Pods which are connected via an inter Pod network and managed under a single APIC cluster. It is an evaluation of what was earlier called as ‘stretched fabric’.

Features of Cisco ACI Multi-Pod

  • Multi-Pod offers resiliency at network level across Pods and rest of the functionality remains with Single ACI fabric. Administrative overhead is minimal while extending data centre network
  • Connectivity and control – all Pods within topology are interconnected using an IP routed inter-Pod network (IPN) which is not managed by APIC but user can configure it separately. All inter-Pod traffic is encapsulated with VXLAN. Control plane between Pod leverages MP-BGP EVPN so endpoint information is propagated in one Pod to an endpoint to another Pod in a seamless manner.
  • Ease of administration – All leaf and Spine switches deployed across Pod come under one Single APIC cluster which means they are considered a single administrative domain.

 

Use cases for Cisco ACI Multi-Pod

  • Enhanced scalability for a large data centre footprint
  • Campus data centre deployments
  • Setting up disaster recovery sites

 

About Cisco ACI Multi-Site

ACI Multi-site is two or more fabrics (having its own APIC cluster) that are managed as a unit using ACI multi-site orchestrator. Each ACI site has a single APIC cluster managing spine leaf fabric. This is ideal where complete isolation is a requirement both at network and tenant change domain levels across ACI network setups.

Features of Cisco ACI Multi-Site

  • Each fabric considered a separate availability zone to ensure business continuance
  • Multi-site utilizes VXLAN for data plane communication between sites and MP-BGP EVPN as the inter site control plane
  • ACI Multi-site extends a layer 2 domain across data centre boundaries in simpler manner
  • Multi-site orchestrator (MSO) serves as a central point to monitor health of ACI sites and application of configurations to multiple sites in one go.

Use cases for Cisco ACI Multi-Site

  • Interconnecting multiple independent, geographically dispersed data centres
  • Disaster recovery scenarios support
  • Highly scalable active active data centres

 

Comparison Table: Cisco ACI Multi-Pod vs Multi-Site

Below able summarizes the difference between the two:

PARAMETER

CISCO ACI MULTI-POD

CISCO ACI MULTI-SITE

ACI Functionality Full ACI functionality across Multi-Pod fabric Multi-sites have tenants, Applications, VREs, BDs, Subnets, EPGs, policies pushed across ACI fabrics
Availability Single availability zone with one APIC cluster Multiple availability zones , each fabric with its separate APIC cluster
VM Migration Supports live VM migration within and across Pods Supports live VM migration within and across sites (vSphere 6 and above) with support of IP mobility across sites
Redundancy Redundant nodes, interfaces and devices within a fabric Full site active / active or active/standby deployment
Configuration Changes APIC cluster pushes configuration changes to Pods fabric (Preserving tenant isolation) Selectively pushing configuration changes to specific sites enable staging/validation (preserving tenant isolation)
Node Count Node count scales as per limits of a single fabric Node count scales as per number of connected sites
Interconnects Uses lower latency IP networks It can deploy policies across continents
Authentication And Role-based Access Control Authentication and RBAC enforced within all Pods of fabric Authentication and RBAC enforced across sites

Download the comparison table: Multi-pod vs Multi-site

Continue Reading:

Cisco ACI vs Cisco DNA

What is Cisco ACI Tenant?

Cisco ACI Network Centric vs Application Centric approach

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