STP and ACI

[Jaya_tv]

Hello,

We have DC1 and DC2(ACI fabric).

DC1 and DC2 are connected through 2 x 10gig Dark fiber links.

I have connected L2 switch(remote Location) in ACI fabric and running PVST for VLAN 90,91 and 200,

Any STP configuration should be considered for this design?

As per the Cisco white paper only for MST, we need to make a special configuration in ACI.

If you see y diagram I have some L2 switch in DC2 which is connected to ACI fabric as L2 through VPC.

L2 switch is on a remote location and 2 links are 10 gig dark fiber from different ISP.
The main purpose of using STP here is for utilizing both ISP 1 and ISP 2 links as active.

Example Vlan 10 will be FWD in ISP 1 and BLK in ISP2
Vlan 20 will be FWD in ISP 2 and BLK in ISP1

Odd VLANs - ISP 1

Even Vlans - ISP 2

In this case, I cannot disable BDPDU filtering in the L2 link otherwise whole above scenario will not work.

Using as L3 is ruled out and also VPC is also ruled out due to different carriers.

Attached topology diagram
Questions

1. How STP link type to be configured (P2P or shared)
Note, I am using only ONE l2 switch running STP.

2. Do I need to worry about TCN ?

[Sergiu.Daniluk]

Hi @Jaya_tv 

I think a better solution would be to configure the two links (red and blue) into a vPC port-channel. This way, you will have both links in FW for both vlans, and you will not have to worry about STP BPDUs.

Regards,

Sergiu

[Jaya_tv]

Blue and red links are from the different carrier so the customer is not preferring VPC so they are using STP for redundancy.

They are using the ODD and EVEN clan concept for utilizing both links as active.

[Sergiu.Daniluk]

Hello,

In that case if you want to use individual links with active Odd/Even vlan pairs, you will need to consider the following:

+ the L2 switch connected in vPC needs to be the STP root

+ all the switch interfaces facing the ACI should be stp link type shared.

+ the vlans allocated to both switches (L2 sw and Core branch sw) should be part of the same VLAN pool on ACI side (to make sure BPDUs will be forwarded between them)

+ If TCNs will be received from either of the switches, ACI will flush the endpoints from EPG in which TCNs are received, but that is expected mechanism so no need to worry about it. It is same as flushing MAC table when TCNs are received.

Stay safe,

Sergiu

[00unsv8e5cJnFPrmC5d6]

I even have an trouble with the xCommand calls, with a bit of luck you can help. If I run the macros from the WebUI then the TC10 layout changes, all proper review. If I call the macro from xCommand then despite the fact that the WebUI indicates the macros as going for walks, the TC10 layout does now not exchange, any thoughts?