Category: Software Defined Datacenters

It’s one of those articles aimed at the people with Cisco ACI experience who don’t bother with reading all the install and other guides again while going through n’th time of building and ACI fabric, like me. When it comes to Cisco ACI, you really should.

There’s a small change with the physical build of the third generation of APIC server where 10G SFP interfaces from APIC towards the Leaf switches (used for fabric discovery and later for the in-band controller to fabric communication) where 4x10G card is built in the server and not like 2x10G on M2/L2 and other first and second generation of APICs.

When you see those 4x10G ports on the server, the logical thing to do will be to use the first two ports on each APIC and connect them to two Leafs (for redundancy and stuff). It ended up being that is not really how Cisco intended those interfaces to be used and it will end up blowing your fabric stability and management. I was able to discover the fabric and register the fabric leaf and spines. It was even possible to configure the whole thing up to the functional fabric and L2-L3 functions but the APIC cluster was always unstable and going in and out of configuration stale and data diverged statuses on cluster view.

SDDC – Software-Defined Data Centers

Times of Software Defined everything has long since arrived, the need to implement many appliances, two or more for each network function, is not so popular anymore. The possibility to manage packet forwarding, load balancing and security of network traffic inside the datacenter from one simple web console is showing finally that things can be managed in a simpler way after all. All vendors in the networking world tried to come up with their own way of centralizing data center management, as it ends up, all of them did it, some better than the others. As always, it’s not a surprise that some vendors are better in creating hardware-based forwarding solutions and some others in software solutions (in this case, software for packet forwarding).

Requirements

It seems that we have basically only a few good options when wanting to select a complete SDDC solution. The data center needs to provide a large number of server access ports in the form of networking devices that are configured and managed as simply and promptly as possible. Datacenter network needs to be configured in a way to provide robustness and stability of packet forwarding at almost line rate and all that at 10-100, even 400Gbps speeds.

API Calls method

The fancy way of configuring Cisco ACI Fabric is by using Python script for generating API calls. Those API calls are then used to configure Cisco ACI by pushing those calls to APIC controller using POSTMAN (or similar tool). Configuration changes done this way are those that you are doing often and without much chance of making mistakes.

You write a Python script and that script will take your configuration variables and generate API call that will configure the system quickly and correctly every time.

The thing is that you need to take the API call example and use Python to write a script that will recreate that API calls with your variables of configuration and do that correctly. You need to know to code in Python and you will need a certain amount of time to write that script.

POST JSON file method

If you are configuring Cisco ACI datacenter fabric it will sooner or later get to the point that you need to configure multiple objects inside the GUI which will, by using the click-n-click method, take a huge amount of time.

While using POSTMAN to create multiple objects of the same type is the preferred method that everybody is speaking about (because you can generate REST API calls using Python or something similar), the quickest way to do it is using POST of JSON configuration file directly through the GUI.

POSTing JSON config example

As described above, the POST of JSON for some simple yet repetitive configuration is the way to go. Let’s see how it’s done:

Creating multiple BDs inside a tenant in Cisco ACI:

Sometimes you will have some L2 domains (Bridge Domains – BD) in your datacenter that will be used with hardware appliances like F5 NLB or something like an additional firewall, WAF or something similar. That is the case where ACI will not route or bridge but the only L3 point of exit from that kind of segment would be on actual hardware appliance outside ACI Fabric – connected to the Leaf port.

We will take an example here and use it throughout the article where BIG IP F5 NLB is used as an L3 termination of L2 BD 10.10.10.0/24.

F5 is directly connected to ACI Leaf and routing from 10.10.10.0/24 subnet (L2 BD) is done directly on F5 device which is default gateway for that subnet endpoints.

In those cases for some particular implementations when you decide not to use PBR or Service graphs, it will happen that appliances like our F5 would become L3 termination for some ACI L2 BD like the 10.10.10.0/24 from my beautiful image above.