NSX Advanced Load Balancer uses virtual services and virtual IP addresses (VIPs). These are related but separate things. This section discusses the differences between VIP and a virtual service.
Virtual IP (VIP): A single IP address owned and advertised by a SE.
Virtual Service: A VIP plus layer 4 protocol ports used to proxy an application. A single VIP can have multiple virtual services. For example, all the following virtual services can exist on a single VIP:
192.168.1.1:80,443 (HTTP/S)
192.168.1.1:20,21 (FTP)
192.168.1.1:53 (DNS)
The VIP in this example is 192.168.1.1. The services are HTTP/S, FTP, and DNS. Thus, VS HTTPS is advertised with address 192.168.1.1:80,443, which is the VIP plus protocol port 443.
The VIP concept is essential in NSX Advanced Load Balancer because a given IP address can be advertised (ARPed) from only a single SE. If the SE that owns a VIP is busy and needs to migrate a virtual service’s traffic to a less active SE, then all the virtual services are moved from the busy SE to the same new (less busy) SE. If an SE fails, all of its virtual services would be moved to a single SE. This is true even if multiple idle SEs are available in the SE group.
