One address, many machines — the balancer decides.
In this interactive Infrastructure lesson from Stencel Academy you don't just read — you type real commands like curl -s https://api.stencel.ai/whoami, ssh admin@lb-01 tail -4 /var/log/haproxy.log and watch the machine respond on a live, animated map. It is part of the free How Infrastructure Works course.
Builds on: Firewalls & Security Groups.
ssh admin@web-02 sudo systemctl stop nginx — Kill a backend — then curl /whoami again and watch the pool shrink.ssh admin@web-02 sudo systemctl start nginx — Bring web-02 back; the next health check re-adds it.dig +short api.stencel.ai — One address in DNS — the pool is invisible from outside.ssh admin@lb-01 cat /etc/haproxy/haproxy.cfg — The whole trick is four lines of config.