VMware NSX-T : Basics about Gateway Router and Segment/Logical Switch

Earlier we talked about the Gateway Firewall in VMware NSX-T environment, Now we are going to discuss about the Gateway Router, Segment and Logical Switch in VMware NSX-T 2.5. 

Gateway Router
NSX-T routing entity that provides distributed East-West routing. A gateway router also  links a Tier-1 router with a Tier-0 router.

Logical Router Port
Logical network port which can attach to either a logical switch segment port or a  physical network uplink port. Logical Router Ports are also used to connect the LR to SR  services such as Network Address Translation (NAT), Load Balancing, Gateway Firewall,  VPN etc.

Fig 1.1- Logical router components

Tier-0 (T0) Logical Router
Provider gateway router is also known as Tier-0 gateway router, and interfaces with the  physical network. Tier-0 gateway router is a top-tier router and can be configured as an  active-active or active-standby cluster of service routers. 

The gateway router runs BGP  and peers with physical routers via the service router. In active-standby mode, the  gateway router can also provide stateful services.

Fig 1.2- Tier 0 Logical router in VMware NSX-T

Tier-1 (T1) Gateway Router
Tier-1 gateway router is the second tier router that connects to one Tier-0 gateway  router for northbound connectivity, and one or more overlay networks for southbound  connectivity. 

Tier-1 gateway router can also be configured in an active-standby cluster of  services when the router is configured to provide stateful services.

Segment / Logical Switch
Segments, called logical switches in previous versions of NSX, are API entities that  provide virtual Layer 2 switching for both VM and router interfaces. 

A segment gives  tenant network administrators the logical equivalent of a physical Layer 2 switch,  allowing a group of VMs to communicate on a common broadcast domain. 

A segment is  a logical entity that exists independent of the underlying infrastructure and spans many  hypervisors. It provides network connectivity to VMs regardless of their physical  location, allowing them to migrate between locations without requiring any  reconfiguration.

Logical Switch Port
Logical switch attachment point to establish a connection to a virtual machine network  interface or a logical router interface. The logical switch port reports applied switching  profile, port state, and link status.