Overview - Getting Traffic into a Cluster | Developer Guide

OpenShift Container Platform provides multiple methods for communicating from outside the cluster with services running in the cluster.

The procedures in this section require prerequisites performed by the cluster administrator.

Administrators can expose a service endpoint that external traffic can reach, by assigning a unique external IP address to that service from a range of external IP addresses. Administrators can designate a range of addresses using a CIDR notation, which allows an application user to make a request against the cluster for an external IP address.

Each IP address should be assigned to only one service to ensure that each service has a unique endpoint. Potential port clashes are handled on a first-come, first-served basis.

The recommendation, in order or preference, is:

If you have HTTP/HTTPS, use a router.
If you have a TLS-encrypted protocol other than HTTPS (for example, TLS with the SNI header), use a router.
Otherwise, use a Load Balancer, an External IP, or a nodeport.

Method	Purpose
Use a router	Allows access to HTTP/HTTPS traffic and TLS-encrypted protocols other than HTTPS (for example, TLS with the SNI header).
Automatically Assign a Public IP Using a Load Balancer Service	Allows traffic to non-standard ports through an IP address assigned from a pool.
Manually assign an external IP to a service	Allows traffic to non-standard ports through a specific IP address.
Configure a nodeport	Expose a service on all nodes in the cluster.

Method

Purpose

Use a router

Allows access to HTTP/HTTPS traffic and TLS-encrypted protocols other than HTTPS (for example, TLS with the SNI header).

Automatically Assign a Public IP Using a Load Balancer Service

Allows traffic to non-standard ports through an IP address assigned from a pool.

Manually assign an external IP to a service

Allows traffic to non-standard ports through a specific IP address.

Configure a nodeport

Expose a service on all nodes in the cluster.