Data Center Spine-Leaf Topologies

October 30, 2018 at 7:19 pm

Many things have changed in the data center over the last decade or so. In fact, so much has changed that the “old” three-layer model of access, aggregation, and core is no longer ideal. This model focused on a “south to north” flow of data. Thanks to virtualization technologies of data, there is much more of an “east to west” flow of data between virtualized workloads in an expanded layer 2 domain.

spine and leaf

In this new two tier architecture, every leaf layer switch connects to each of the spine switches in a full mesh topology. Of course, the leaf devices connect directly to your servers (hosting God knows how many containers and VMs) and the spine layer forms the high speed core of your network. With each leaf switch connecting to every spine device, traffic is randomly load balanced across the multiple paths that exist, and a failure of a spine device has a very minimal disruption on the overall data center.

Oversubscription issues are handled with ease. New leaf switches are added when ports are in short supply for your servers, and new spine devices can be added when overall bandwidth begins to suffer.

Notice also that this design provides much more predictable latency. This is because server to server communication always involves the same number of devices in the path (unless you get lucky and the servers are connected to the same leaf device).

Spine and leaf topologies lend themselves beautifully to overlay technologies in order to solve many data center challenges. Specific Cisco overlay, spine and leaf architectures include:

  • Cisco FabricPath Spine and Leaf
  • Cisco VXLAN Flood-and-Learn Spine and Leaf
  • Cisco VXLAN MP-BGP Ethernet VPN Spine and Leaf
  • Cisco Massively Scalable Data Center (MSDC) Layer 3 Spine and Leaf

I hope this has been informative for you, and I would like to thank you for reading!

Configuring FabricPath

August 30, 2018 at 11:44 pm

Enjoy this sample Nugget from my latest CCNA Data Center course (200-155) at CBT Nuggets!


Cisco CCNA Data Center 200-155 DCICT Arrives at CBT Nuggets

August 29, 2018 at 6:07 pm


It is here! So many of you have asked about this course and it is now live on the CBT Nuggets site!

Cisco CCNA Data Center 200-155 DCICT

Jeremy Cioara is still hard at work on the other CCNA Data Center course (200-150 DCICN), but keep in mind if you are a CCNA R&S, much of that course (80% or so) will be review.

This course was an incredible amount of fun to create as it covers the very latest technologies found in the modern data center. The Nuggets are as follows:

1. Introduction: The CCNA Data Center
2. Introduction: Getting Your Hands on Equipment
3. Network Virtualization: Module Introduction
4. Network Virtualization: Functional Planes
5. Network Virtualization: CoPP
6. Network Virtualization: Stateful Fault Recovery
7. Network Virtualization: Virtual Routing and Forwarding
8. Network Virtualization: Default and Mgmt VRFs
9. Network Virtualization: Virtual Device Contexts
10. Network Virtualization: VDC Resources
11. Network Virtualization: VDC Context Types
12. Network Virtualization: VDC Resource Allocation
13. Network Virtualization: Managing VDCs
14. Network Virtualization: A VDC STP Example
15. Network Virtualization: Introducing Overlay Networks
16. Network Virtualization: VXLAN
17. Network Virtualization: NVGRE
18. Network Virtualization: You Down with OTV?
19. Network Virtualization: OTV Basic Operations
20. Cisco DC Networking: FEX
21. Cisco DC Networking: FEX Options
22. Cisco DC Networking: vPC
23. Cisco DC Networking: Configuring a vPC
24. Cisco DC Networking: FabricPath
25. Cisco DC Networking: Configuring FabricPath
26. Cisco DC Networking: Unified Switch Ports
27. Cisco DC Networking: Unified Fabric
28. Cisco DC Networking: FCoE
29. Unified Computing: Virtual Machines
30. Unified Computing: Hypervisors
31. Unified Computing: Installing the ESXi Hypervisor
32. Unified Computing: Using Hyper-V
33. Unified Computing: Virtual Machine Manager
34. Unified Computing: Virtual Switches
35. Unified Computing: Creating a Standard vSwitch
36. Unified Computing: Cisco 1000V
37. Unified Computing: 1000V Operations
38. Unified Computing: Shared Storage
39. Unified Computing: Configuring Shared Storage
40. Unified Computing: vMotion and Migration
41. Unified Computing: Server Types
42. Unified Computing: UCS Components
43. Unified Computing: Hardware Abstraction
44. Unified Computing: RBAC
45. Unified Computing: Basic UCS Config
46. Unified Computing: Service Profiles
47. Orchestration: Cloud Concepts
48. Orchestration: APIs
49. Orchestration: UCS Director
50. Orchestration: UCS Director Workflows
51. ACI: Architecture
52. ACI: Fabric Discovery
53. ACI: Policy Driven Model
54. ACI: The Logical Model
55. ACI: Programmability
56. ACI: Orchestration Options

Cisco ACI Introduction – Part 3 – The Logical Components

August 18, 2018 at 6:19 pm

Cisco ACI

It is critical that you understand the physical components and protocols discussed in Part 2, but it is also critical that you understand the logical constructs used within the ACI system. You might need to create some Flash Cards on these until they are second nature.

  • Tenant: Contains policies that enable qualified users to have domain-based access control. Qualified users can access privileges such as tenant administration and networking administration.
  • Context: A context is a unique Layer 3 forwarding and application policy domain. A tenant can have multiple contexts. A context is often defined with VRFs.
  • Bridge domain: A bridge domain represents a Layer 2 forwarding construct within the fabric. A bridge domain must link to a context and have at least one subnet associated with it. The bridge domain defines the unique Layer 2 MAC address space and a Layer 2 flood domain if such flooding is enabled.
  • EPG: The EPG is a managed object that contains a collection of endpoints (devices that are connected to the network directly or indirectly) that have common policy requirements such as security, virtual machine mobility, QoS, or Layer 4 to Layer 7 services. Endpoints have an address (identity), a location, attributes (such as version or patch level), and a physical or virtual status. Rather than configure and manage endpoints individually, they are placed in an EPG and are managed as a group. EPGs are fully decoupled from the physical and logical topology, and endpoint membership in an EPG can be dynamic or static.
  • Application network profile: An application profile models the application requirements, and it is a convenient logical container for grouping EPGs.
  • Contract: The contract governs the types of endpoint group traffic that can pass between EPGs, including the protocols and ports that are allowed. If there is no contract, inter-EPG communication is disabled by default. No contract is required for intra-EPG communication. EPGs can only communicate with other EPGs according to the contract rules.
  • Filter: The filter sorts Layer 2 to Layer 4 fields, TCP/IP header fields such as Layer 3 protocol type, Layer 4 ports, and so on.
  • Subject: Within a contract, subjects use filters to specify the type of traffic that can be communicated, and how it occurs. Subjects determine whether filters are unidirectional or bidirectional. Contract subjects contain associations to the filters (and their directions) that are applied between EPGs that produce and consume the contract.

Wrapping Up 200-155 CCNA Data Center Today!

August 17, 2018 at 1:14 pm


I wanted to make this post because so many of you have asked me about a completion date for this exciting new CBT Nuggets content. I am indeed wrapping up the final videos today! This makes it very close to release on the CBT Nuggets website. Woohoo!

I will be sure to follow up with another post in the next couple of business days on the exact date of availability on the CBT Nuggets site. By the way, the final Nugget count looks like it is going to come in about 55! They cover the following:

  • NX-OS
  • Orchestration
  • ACI
  • UCS
  • Virtualization

and many more topics critical for the modern, Cisco-centric data center. And of course, many topics are not JUST Cisco focused. Enjoy!