An NSX-T logical router reproduces routing functionality in a virtual environment completely decoupled from underlying hardware. The tier-0 logical router provides an on and off gateway service between the logical and physical network.
An NSX Edge cluster can back multiple tier-0 logical routers. Tier-0 routers support the BGP dynamic routing protocol and ECMP.
When you add a tier-0 logical router, it is important that you map out the networking topology you are building.
For simplicity, the sample topology shows a single tier-1 logical router connected to a single tier-0 logical router hosted on a single NSX Edge node. Keep in mind that this is not a recommended topology. Ideally, you should have a minimum of two NSX Edge nodes to take full advantage of the logical router design.
The tier-1 logical router has a web logical switch and an app logical switch with respective VMs attached. The router-link switch between the tier-1 router and the tier-0 router is created automatically when you attach the tier-1 router to the tier-0 router. Thus, this switch is labeled as system generated.