Choosing Symmetrical vs. Asyymetrical IRB (eVPN) with VXLAN underlay & NSX

[Alex Tanner]

Hi

I was wondering if anyone had any opinions, viewpoints, experience around the use of NSX-T integrating it into an environment configured with either an Asymmetrical IRB (for reference https://www.networkworld.com/article/2344468/how-does-vlan-routing-and-bridging-work-when-using-irb-.html) or Symmetrical IRB configured underlay and whether there were any specific considerations for NSX-T northbound traffic via the Tier 0s (and / or VRFs).

This is not an area of expertise for me - so please excuse any idiot statements

As I understand it the choice of Symmetrical or Asymmetrical IRB is about scale, automation, ease of deployment and consistency of configuration. (https://www.nullzero.co.uk/evpn-vxlan-symmetrical-irb-versus-asymmetrical-irb/)

My question is not really designed as an ask around the respective merits of Symmetrical vs Asymmetrical IRB, but more around whether the choice of one or the other versions of IRB has an impact on how one would deploy and interact with NSX-T (such as I assume the fact that NSX support EVPN Type-5 and not Type-2 or Type-3 AFAIK)

Any experience or thoughts very much appreciated as Dr Google has not exposed much in the way of collateral of discussion

Many thanks

[Sree]

Symmetric is ideally preferred as we have a much better control plane scaling. That being said, whether we have EVPN VXLAN Control plane session or traditional routing peering if control plane scalability is a concern for the physical fabric, symmetric IRB is better in my opinion because we need VNI and SVI mapping on all leaf in the fabric if the choice is Asymmetric IRB.