Cisco ACI Multi-Site spines back-to-back

[m1xed0s]

I guess the whitepage below for the ACI multisite is not clear.

https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-739609.html

I am trying to understand if MSO is still required for the ACI multisite architecture using spines back-to-back connectivity?

[Timothy Rothenberg]

Yes, each site needs it's own APIC cluster and then the deployment needs a MSO cluster to manage both fabrics.

[m1xed0s]

Okey. So what if I do not purchase license for MSO, can I still use the spines back-to-back architecture to interconnect two ACI fabric sites (say using a L2 DCI as transport between)? I am okey to apply configuration using independent APIC in the site though...

So what would be the down sides OR this would not even work? ODD scenario for sure...

[Marcel Zehnder]

Yes MSO is still required. With the spine backt-to-back architecture you won't need a ISN (inter site network). However, this is only supported for two sites. As soon as you want do deploy a 3rd site you need an ISN.

[m1xed0s]

So without MSO, this spine back-to-back architecture won’t work? Even I just do manual setup to connect the two and manual configure in each site? Only two sites.

[Marcel Zehnder]

Hmmm, I've never tried that... ...well it should work from my point of view because the MSO is not involved in either forwarding nor endpoint learning...I recommend you lab it up.

[m1xed0s]

Okey, I think it is possible and that’s why the white paper was not stating the MSO role for back-to-back...

but MSO typically help build the inter site connection automatically so how to setup that connection manually...Hope someone from Cisco could share some.

[Hector Gustavo Serrano Gutierrez · Accepted solution]

Greetings!

Indeed, the ACI Multi-Site solution requires of the MSO controller. There's no way around it. Even if go to the APICs on both sites and manually configure the back-to-back links on the Spines in the "infra" tenant, you need to use the MSO controller to push the policies to the APICs for the correct programming of VNI and Class-ID translations on Spine Switches so traffic can be forwarded smoothly site to site.

[m1xed0s]

Thanks! I am clear now.