ACI L3Out L3 interface concept of VLAN

[hamed1900]

Hi Guys,

Need to configure point to point L3 interface between ACI and Cisco router's interface.

Based on the documentation, on ACI, I need to configure L3DOMAIN -->  which contains VLAN/s.

I do not understand why we have configured VLAN for this scenario, the other end is a routed interface, and I cannot leave the VLAN section blank on the ACI though, what that VLAN does??

Can someone explain the reason for it?

Thanks,

Hamed

[RedNectar · Accepted solution]

It's an anomaly in the process.  Yes, you will get an error if you don't link your Tenant's External Routed Network (aka L3 Out) to an External Routed Domain but, as you say, if you are configuring a routed interface, you don't need any VLANs!

However, you need the link between your Tenant's L3 Out to the External Routed Domain because the External Routed Domain links to an Attachable Access Entity Profile that links to the Access Port Policy Group (or V/PC Interface Policy Group) that contains the policies that you need applied to your routed port (CDP, LLDP etc).  Then of course, the Access Port Policy Group (or V/PC Interface Policy Group) needs to be linked to the Interface Selector/Interface Profile/Leaf Profile combination that defines the port that you are defining as your Routed Interface so the polices (CDP, LLDP etc) are applied to the correct port.

It's only the VLAN association that is not strictly required, and (last time I check which was a couple of releases ago) you could actually get away with not having a VLAN Pool linked to the External Routed Domain and the L3 Out would still work OK, even though it left an annoying error agains the L3 Out.

HTH

RedNectar
aka Chris Welsh

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[hamed1900]

Thanks Chris,

Hamed