ACI architecture without spine swicth

[marine253]

Hello ,

I am getting a bit confused with the Leaf-spine architecture for ACI.

As per cisco website the Cisco Nexus 93180YC-EX Switch is considered as a ACI-leaf switch.

Let's say that i have only 2 leaf switches (Cisco Nexus 93180YC-EX Switch) connected to each other via fiber and I want to deploy ACI. Will this architecture work without an official "Spine switch" ( such as the Cisco Nexus 9364C Switches or  Cisco Nexus 9500 platform switches with -EX or -FX line cards and -E or -E2 fabric modules)

Based on what i've read so far , all the ACI architecture requires a leaf-spine architecture.

In terms of buget a spine switch seems to be an overkill and it does not make sense to me to purchase an additional hardware if it is not required.

Multi-site ACI is also being considered here.

[RedNectar]

Hi marine253,

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Let's say that i have only 2 leaf switches (Cisco Nexus 93180YC-EX Switch) connected to each other via fiber and I want to deploy ACI. 

STOP THERE - you can't do that - end of story. You can't connect leaf switches to leaf switches - the whole idea that Mr Charles Clos came up with in 1952 of a Leaf and Spine topology is only scalable because of this rule.

However, you CAN deploy the Cisco Nexus 93180YC-EX Switch in NX-OS mode, and then you can quite happily connect them todether.

Now back to your question

In terms of buget a spine switch seems to be an overkill and it does not make sense to me to purchase an additional hardware if it is not required.

Absolutely - if all you need is two Cisco Nexus 93180YC-EX Switches then I would recommend that you DO NOT CONSIDER ACI.  That is unless you plan to scale to something bigger in the future or want to start taking advantage of other ACI features right away.  Having said that, I have seen many installations of ACI with as few as 4 or 6 leaf switches where the plan is to scale to something larger, and/or the company wants to start taking advantage of centralised management or application profiles immediately.

So the bottom line is that you have to ask yourself what you are trying to achieve.  If you want the ACI features, you must implement a leaf/spine topology - which means you need two spines at least, not one. (It WILL work with one spine, but not supported by Cisco except in the case of a failure of one spine)

On the other hand, if all you want is port density, at a scale of two switches, ACI does not make sense.

[marine253]

Hello Chris,

Thanks a lot for your expert advise.

The customer is going full fledge NX-OS at first , then in the near future will be moving towards ACI. They just want to know their options.

1 more question , the 93180YC-EX as an ACI leaf is okay right? Assuming they go the recommended way ( Leaf-Spine).

I've heard the Cisco 9k has some kind of reduced NX-OS funtionalities...

[RedNectar · Accepted solution]

Hi marine253,

Thanks a lot for your expert advise.

My pleaseure. Thanks for the accolade

The customer is going full fledge NX-OS at first , then in the near future will be moving towards ACI. They just want to know their options.

Moving from NX-OS to ACI later IS an option, but not without problems. If ACI is definately their final goal (maybe the abilty to manage two sites from a single point is good enough reason - I missed that point from your original post)

1 more question , the 93180YC-EX as an ACI leaf is okay right? Assuming they go the recommended way ( Leaf-Spine).

The 93180YC-EX is a very fine ACI leaf switch. And the Nexus 9332C is a very fine Spine switch. Both models support NX-OS and ACI modes - but of course the ACI licence is an additional cost if you want to migrate later.

I've heard the Cisco 9k has some kind of reduced NX-OS funtionalities...

Reduced compared to what? If you compare the Nexus 9K with say the Nexus 7K, then there are certain things that the 7K can do that are just not what the 9K was designed to do - OTV, Fabric Path, MPLS... I'm not aware of any differences that would matter in the scenario you describe. 

[patrick.morin]

The 93180YC-EX is a very fine ACI leaf switch. And the Nexus 9332C is a very fine Spine switch. Both models support NX-OS and ACI modes - but of course the ACI licence is an additional cost if you want to migrate later.

The APIC servers (plural) are also an additional cost.