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deepak21bhandari
Beginner

What is the use of separate Vtep Pool in Multipod scenarios in ACI.

Hi All,

 

Can some one please explain me what is the use of different VTEP Pool (IP) in each multipod site.

as i know leaf and spine get tep IP addresses in each pod from Seed pod (Primary POD) then what is the use of different TEP pool in all multipod sites.

 

Thanks in advance

Dheerander Singh

3 REPLIES 3
Sergiu.Daniluk
VIP Advocate

What you mentioned  - "as i know leaf and spine get tep IP addresses in each pod from Seed pod (Primary POD)"  - it's partially inaccurate.

It's true that one of the APICs from Primary POD is the one which assigned the TEP address for nodes in Pod2 (when the new pod is initialized), however, the IP address assigned is from the VTEP Pool configured for Pod2.

Read more about it in the ACI Multi-Pod whitepaper - section IPN control plane (Figure 8):

https://www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/application-centric-infrastructure/white-paper-c11-737855.html#InterPodConnectivityDeploymentConsiderations

 

Stay safe,

Sergiu

 

Hi Sergiu,

Thanks for you reply but still i am bit confused as you said (however, the IP address assigned is from the VTEP Pool configured for Pod2) you mean to say that leaf and spine in another pods get IP addresses from Pod 2 Tep pool?

 

Can you please explain little more about it?

 

Regards

Dheerander 

RedNectar
Engager

Hi Dheerander,

To answer you question: "what is the use of different VTEP Pool (IP) in each multipod site?" - look at this diagram from the paper @Sergiu.Daniluk referred to:

image.png

As you can see, the IPN routing table requires a different summary range for each pod. 

I suppose the designers COULD have used /32 routes throughout the routing table and allocated the IP addresses for the 2nd (3rd, 4th..) pod from the same pool, but this would have beed a VERY BAD idea, because when you initially set up your first pod, you (presumably) assigned a VTEP Pool sized on pod1 - so trying to squeeze more IP addresses out of this pool is a design for disaster - especially since the only way to re-assign the VTEP pool is to re-initialise the WHOLE pod.

 

 

RedNectar
aka Chris Welsh


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