Protocols and Ports

Frontend Protocols and Ports

Frontend protocols and ports are used by load balancers to receive requests from clients. Load balancers use TCP or UDP at Layer 4, and HTTP or HTTPS at Layer 7. Select a protocol and a port that best suit your needs.

Protocol	Port
TCP	For one load balancer: The port numbers of different protocols must be unique except UDP. Specifically, the port numbers used by UDP can be the same as those of other protocols. For example, if you have a UDP listener that uses port 88, you can add a TCP, HTTP, or HTTPS listener that also uses port 88. However, if you already have an HTTP listener that uses port 443, you cannot add an HTTPS or TCP listener with the same port. The port numbers of the same protocol must be unique. For example, if you have a TCP listener that uses port 80, you cannot add another listener with the same port. The port numbers range from 1 to 65535. The following are some commonly-used protocols and port numbers: TCP/80 HTTPS/443
UDP
HTTP
HTTPS

Backend Protocols and Ports

Backend protocols and ports are used by backend servers to receive requests from load balancers. If Windows servers have Internet Information Services (IIS) installed, the default backend protocol and port are HTTP and 80.

**Table 1** Backend protocols and ports
Protocol	Port
TCP	Backend ports of the same load balancer can also be the same. The port numbers range from 1 to 65535. The following are some commonly-used protocols and port numbers: TCP/80 HTTP/443
UDP
HTTP