Impact of reducing dynamic Vlan Pool - used for VMM

[Stefan Engel]

Hi Community,

We currently have the following dynamic vlan pool assigned VMM domain: vlan 1000-1999.

As the assignment is dynamic, we see port-encap for EPG's assigned to VMM all over. 

We are planning to reducing the pool to 1000-1100. 

Question:

will each EPG assigned to the VMM domain, automatically/seamless just assign a new vlan out of the new pool (some are currently using valn-encap above 1100)? 

should we expect any interruption or is this seamless? 

Thanks,

Stefan

[ashok_boin]

Hi Stefan,

I am not sure whether there would be any complications but it's not actually a recommended approach to reduce VLAN Pool.

The following link may help...

Solved: VLAN Pool sizing - Cisco Community

[Stefan Engel]

Thanks a lot @RedNectar for taking the time & sharing this. All clear now.

[ashok_boin]

Excellent. Thanks a lot, @RedNectar 

[Sergiu.Daniluk]

Chris, wow! You just opened the door to a new way of answering on cisco community.

Bravo!

Sergiu

[Robert Burns]

To add to Chris' excellent video (video is worth a thousand words) - I did one additional test by "changing" the VLAN range completely.  I know in the OP's case they wanted to reduce the existing range, in my case it was moving the VMM domain to an entirely different range.  It's not as involved as reducing an existing range.  If you have an existing VLAN pool assigned to a VMM domain, you can't change that VLAN pool assigned while it's in use, but you can however add another VLAN range block to the existing pool in use, then remove the original one.  This will cause a very briefly disruption, but the APIC will re-assign all bound EPGs automatically to the new VLAN range, without having to migrate the endpoints out of the Port Groups (to quarantine) and back.  

Summary:

1) Adding/Expanding Existing VLAN Pool: Easy, no impact

2) Reducing Existing Range: Moderate Effort, with moderate impact

3) Changing Existing Pool to different VLAN Range: Easy, brief impact

Robert

[Stefan Engel]

Thanks for the additional information @Robert Burns, very helpful!