diff --git a/README.md b/README.md
index 9405fa3e..38ff4edf 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,8 @@ can be used.
 
 If you are new to Prometheus and `node_exporter` there is a [simple step-by-step guide](https://prometheus.io/docs/guides/node-exporter/).
 
+The `node_exporter` listens on HTTP port 9100 by default. See the `--help` output for more options.
+
 ### Ansible
 
 For automated installs with [Ansible](https://www.ansible.com/), there is the [Cloud Alchemy role](https://github.com/cloudalchemy/ansible-node-exporter).