Good day everyone,

I am trying to understand what the ECMP option under the various routing protocols accomplishes in NSX-T e.g. under BGP when deploying an active-active Tier 0 SR and documentation is not particularly clear on this. Configuration-wise active-active HA for a T0 gateway and ECMP under BGP are completely different configuration options, yet the difference is not particularly clear to me and I feel like these two concepts get used interchangeably (incorrectly) in the documentation.

Does the ECMP option allow a given active edge instance of a T0 SR to load-balance across multiple (local) upstream paths (e.g. one of the active edges has 4 upstream peers and load-balances traffic across all 4 peers) or does this ECMP option somehow influence the traffic pattern from the Tier 0/Tier 1 DR towards the Tier 0 SR edges?

I've managed to disable ECMP and inter-SR routing on an active-active T0 SR edge but I do not see any change in traffic patterns (note that both active edges have a single upstream peer i.e. same upstream physical router peering from the two active edges in this sample topology). What should be happening in such a scenario?

Any clarifications on this would be much appreciated.