Prometheus supports integration with multiple Alertmanager instances for redundancy and high availability. The alerting section of the Prometheus configuration file (prometheus.yml) allows specifying a list of Alertmanager targets, enabling Prometheus to send alerts to several Alertmanager nodes simultaneously.
There is no hard-coded limit on the number of Alertmanagers that can be added. The typical best practice is to run a minimum of three Alertmanagers in a clustered setup to achieve fault tolerance and ensure reliable alert delivery, but Prometheus can be configured with more than three if desired.
Each Alertmanager node in the cluster communicates state information (active, silenced, inhibited alerts) with its peers to maintain consistency.
Reference:
Verified from Prometheus documentation - Alertmanager Integration, High Availability Setup, and Prometheus Configuration - alerting Section.