ACI N7K VPC configuration

[Luke Poskitt]

Hi Guys,

I've connected my test UCS to my test ACI fabric using a vPC per fabric interconnect on my two leaf nodes, and I've connected my test ACI fabric to my N7K pair core using a double-sided vPC to my leaf nodes.

I've created a single BD containing a single EPG and a single VLAN and have deployed the EPG onto the three vPCs (UCS-A-vPC, UCS-B-vPC, and N7K-vPC) using the single VLAN ID as the primary encapsulation.

Unfortunately, the single VLAN trunked on the N7K vPC is entering a blocking state almost immediately on enabling the vPC - I can only assume that BPDUs by the ACI fabric on the N7K vPC are being re-broadcast back out the same vPC.

What is the correct spanning-tree port type and bpduguard/bpdufilter configuration that should be used on an N7K layer 2 vPC to the ACI fabric.

Apologies if this is a stupid question, but I can't seem to find this information documented in any white paper, guide, or best practice.

Cheers,

-Luke

[Nik Noltenius · Accepted solution]

Hi Luke,

we have this working on an N7k vPC pair connecting to an ACI fabric:

interface port-channel1
  switchport
  switchport mode trunk
  switchport trunk allowed vlan <x,y,z>
  spanning-tree port type edge trunk
  spanning-tree bpdufilter enable
  mtu 9216
  vpc 1

Hope this helps

Nik

[Luke Poskitt]

Thanks Nik, that solved the problem of the N7K vPC entering a blocking state.

However, I found it was also necessary to enable legacy mode on my bridge domain specifying the single VLAN - on checking, I found that the VLAN wasn't being programmed onto the interfaces/vPCs on which the EPG had been statically deployed, although I'm not sure why.

Cheers,

-Luke

[Luke Poskitt]

As a follow-up; I disabled legacy mode on the BD and selected the "Enable Infrastructure VLAN" checkbox in the "default" AAEP (accidentally - I was meaning to enable it in the AAEP associated with the physical domain being used), and surprisingly this seems to have now programmed the VLAN onto the leaves (e.g. sh vlan extended).

I'm not sure how or why this worked - it continued working after I unselected the "enable Infrastructure VLAN" checkbox and I wasn't able to re-produce the issue seen.

[Shahid Raza]

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