Exposing TCP and UDP ports through ingress NGINX

It is possible to expose ports other than 80 and 443 through the NGINX ingress in Kubernetes.

An example where this is needed is a DNS server which uses port 53 on both TCP and UDP. Pi-hole is a widely self-hosted DNS server that also works as an ad-blocker.

The way to expose those ports is, in a couple of points:

1. Define the app that implements the service and exposes the ports to the cluster via a Kubernetes service;
2. Configure the NGINX ingress controller to accept incoming requests from the ports, and forward them to the service.

There are a couple of caveats:

• NGINX supports UDP load balancing since version 1.9.13;
• Cannot route traffic based on host, only 1 service in the cluster can be exposed with this method;
• There is a bug on the kubectl client that prevents setting the same service ports on both protocols, if using apply, you can use the parameter --server-side=true to mitigate the issue.

Source: https://kubernetes.github.io/ingress-nginx/user-guide/exposing-tcp-udp-services/