Azure VMware Solution: NSX-T Active/Active T0 Edges...but
Azure VMware Solution (AVS) delivers by default w/ a pair of redundant Large NSX-T Edge VM's each running a T0 in active/active mode. So why is my traffic only going out one Edge VM?
The default T1 that is delivered w/ AVS is an active/passive T1 where you connect your workloads to. So while it could technically take either T0, it's always going to go out the closest T0 to the active "SR" T1. Where do the SR's live? You guessed it, on the Edge VM's. As you can imagine, this can lead to a bottleneck if you try to shove all your traffic through a single Edge VM.
The return path could come back via any T0, but guess what, the T0 that receives the packet will pass the traffic to the active "SR" T1 to be processed. Meaning by default, a single EVM will process all in and outbound traffic. It wasn't always this way. AVS used to deploy w/ an active/active T1. So what changed? We needed a way for customers to resolve internal DNS addresses for their vCenter/NSX-T, etc. So was the birth of the NSX-T DNS forwarder on the default T1.
This meant the default T1 transformed into an active/passive one. I highlight by default because, you don't have to use the default T1. It can be simply left alone. You can create as many T1's as is supported by NSX-T. It would be recommended to create T1's for your own workloads.
You have choices when it comes to T1's. You can deploy an active/active or active/passive T1. The basic difference between the two, is whether you attach and Edge Cluster to the T1 or not. Attaching an Edge Cluster enables that T1 to run services like DHCP, DNS, stateful firewall, etc.
|Example of ways T1's can be deployed along the existing default AVS T1.|
- The implementation of ECMP on NSX Edge is based on the 5-tuple of the protocol number, source address, destination address, source port, and destination port.
SR = Service Router
DR = Distributed Router
T0 = Tier-0 Router
T1 = Tier-1 Router
EVM = Edge VM
AVS = Azure VMware Solution