---
title: "Configure Alertmanager"
description: "Configure Alertmanager in a Calico Cloud connected cluster to route Prometheus alerts to operators with deduplication, grouping, silencing, and inhibition rules."
product: "Calico Cloud"
version: "v23.0.1"
section: "Operations"
canonical_url: "https://docs.tigera.io/calico-cloud/operations/monitor/prometheus/alertmanager"
---

# Configure Alertmanager

Alertmanager is used by Calico Cloud to route alerts from Prometheus to the administrators. It handles routing, deduplicating, grouping, silencing and inhibition of alerts.

More detailed information about Alertmanager is available in the [upstream documentation](https://prometheus.io/docs/alerting/latest/configuration).

### Updating the Alertmanager config

- Save the current alertmanager secret, usually named `alertmanager-<your-alertmanager-name>`. Our manifests will end up creating a secret called: `alertmanager-calico-node-alertmanager`.

  ```bash
  kubectl -n tigera-operator get secrets alertmanager-calico-node-alertmanager -o yaml > alertmanager-secret.yaml
  ```

- The current alertmanager.yaml file is encoded and stored inside the `alertmanager.yaml` key under the `data` field. You can decode it by copying the value of `alertmanager.yaml` and using the `base64` command.

  ```bash
  echo "<whatever-you-copied>" | base64 --decode > alertmanager-config.yaml
  ```

- Make necessary changes to `alertmanager-config.yaml`. Once this is done, you have to re-encode and save it to `alertmanager-secret.yaml`. You can do this by (in Linux):

  ```bash
  cat alertmanager-config.yaml | base64 -w 0
  ```

- Paste the output of the running the command above back in `alertmanager-secret.yaml` replacing the value present in `alertmanager.yaml` field. Then apply this updated manifest.

  ```bash
  kubectl -n tigera-operator apply -f alertmanager-secret.yaml
  ```

Your changes should be applied in a few seconds by the config-reloader container inside the alertmanager pod launched by the prometheus-operator (usually named `alertmanager-<your-alertmanager-instance-name>`).

For more advice on writing alertmanager configuration files, see the [alertmanager configuration](https://prometheus.io/docs/alerting/latest/configuration/) documentation.

### Configure Inhibition Rules

Alertmanager has a feature to suppress certain notifications according to defined rules. A typical use case for defining `inhibit` rules is to suppress notifications from a lower priority alert when one with a higher priority is firing. These inhibition rules are defined in the alertmanager configuration file. You can define one by adding this configuration snippet to your `alertmanager.yaml`.

```yaml
[...]
inhibit_rules:
- source_match:
    severity: 'critical'
  target_match:
    severity: 'info'
   # Apply inhibition for alerts generated by the same alerting rule
   # and on the same node.
  equal: ['alertname', 'instance']
[...]
```

### Configure Grouping of Alerts

Alertmanager also has a feature to group alerts based on labels and fine tune how often to resend an alert and so on. In the case of Denied Packet metrics, simply defining a Prometheus alerting rule would mean that you will get an page (if so defined in your alertmanager configuration) for every policy on every node for every Source IP. All these alerts can be combined into a single alert by configuring grouping. The Alertmanager configuration file that is provided with Calico Cloud by default, groups alerts on a per-node basis. Instead, if the goal is to group all alerts with the same name, edit (and apply) the alertmanager configuration file like so:

```yaml
global:
  resolve_timeout: 5m
route:
  group_by: ['alertname']
  group_wait: 30s
  group_interval: 1m
  repeat_interval: 5m
  receiver: 'webhook'
receivers:
  - name: 'webhook'
    webhook_configs:
      - url: 'http://calico-alertmanager-webhook:30501/'
```

More information, including descriptions of the various options can be found under the [route section](https://prometheus.io/docs/alerting/latest/configuration/#route) of the Alertmanager Configuration guide.