T6949: Adds blackbox exporter config example

Author: nvollmar

docs/configuration/service/monitoring.rst

@@ -259,9 +259,24 @@ HTTP, HTTPS, DNS, TCP, ICMP and gRPC .
 
   Configure name of the :abbr:`VRF (Virtual Routing and Forwarding)` instance.
 
-.. cfgcmd:: set service monitoring prometheus blackbox-exporter config-file <path>
+Configuring modules
+-------------------
+Blackbox exporter can be configured with different modules for probing DNS or ICMP.
 
-  Configure a custom config file under `/config/prometheus_exporter/`
+DNS module example:
+
+.. code-block:: none
+
+  set service monitoring prometheus blackbox-exporter modules dns name dns4 preferred-ip-protocol ip4
+  set service monitoring prometheus blackbox-exporter modules dns name dns4 query-type A
+
+ICMP module example:
+
+.. code-block:: none
+
+  set service monitoring prometheus blackbox-exporter modules icmp name ping6 preferred-ip-protocol ip6
+  set service monitoring prometheus blackbox-exporter modules icmp name ping6 ip-protocol-fallback
+  set service monitoring prometheus blackbox-exporter modules icmp name ping6 timeout 3
 
 .. _node_exporter: https://github.com/prometheus/node_exporter
 .. _frr_exporter: https://github.com/tynany/frr_exporter