diff --git a/src/main.rs b/src/main.rs
index cea7a0c..8cfa5e6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -185,12 +185,44 @@ fn resolve_reflectors(
             if protocol != ReflectorProtocol::Irtt && endpoint.is_ipv6() {
                 continue;
             }
-            resolved.insert(endpoint, definition.clone());
+            insert_reflector(&mut resolved, endpoint, definition.clone())?;
         }
     }
     Ok(resolved)
 }
 
+fn insert_reflector(
+    reflectors: &mut HashMap<SocketAddr, ReflectorDefinition>,
+    endpoint: SocketAddr,
+    definition: ReflectorDefinition,
+) -> anyhow::Result<()> {
+    if let Some(existing) = reflectors.get(&endpoint) {
+        let same_country = match (&existing.country, &definition.country) {
+            (Some(a), Some(b)) => a.eq_ignore_ascii_case(b),
+            (None, None) => true,
+            _ => false,
+        };
+        let same_protocols = existing
+            .protocols
+            .iter()
+            .all(|p| definition.protocols.contains(p))
+            && definition
+                .protocols
+                .iter()
+                .all(|p| existing.protocols.contains(p));
+        if !same_country
+            || !same_protocols
+            || existing.irtt_port.unwrap_or(2112) != definition.irtt_port.unwrap_or(2112)
+            || existing.irtt_hmac != definition.irtt_hmac
+        {
+            anyhow::bail!("conflicting reflector definitions for resolved endpoint {endpoint}");
+        }
+    } else {
+        reflectors.insert(endpoint, definition);
+    }
+    Ok(())
+}
+
 fn setup_reflectors(settings: &Settings) -> anyhow::Result<ReflectorSetup> {
     let protocol = settings.advanced_settings.measurement_type;
     let configured = resolve_reflectors(
@@ -201,11 +233,9 @@ fn setup_reflectors(settings: &Settings) -> anyhow::Result<ReflectorSetup> {
     )?;
     let bootstrap = resolve_reflectors(&settings.reflectors.bootstrap, protocol, &[], false)?;
     let mut reflectors = bootstrap.clone();
-    reflectors.extend(
-        configured
-            .iter()
-            .map(|(endpoint, definition)| (*endpoint, definition.clone())),
-    );
+    for (endpoint, definition) in &configured {
+        insert_reflector(&mut reflectors, *endpoint, definition.clone())?;
+    }
     if reflectors.is_empty() {
         anyhow::bail!("no usable reflectors for measurement protocol {protocol}");
     }