[distributed][misc] error on same VLLM_HOST_IP setting (#7756)

vllm/executor/ray_gpu_executor.py

@@ -218,6 +218,19 @@ class RayGPUExecutor(DistributedGPUExecutor):
         for node_id, gpu_ids in node_gpus.items():
             node_gpus[node_id] = sorted(gpu_ids)
 
+        all_ips = set(worker_ips + [driver_ip])
+        n_ips = len(all_ips)
+        n_nodes = len(node_workers)
+
+        if n_nodes != n_ips:
+            raise RuntimeError(
+                f"Every node should have a unique IP address. Got {n_nodes}"
+                f" nodes with node ids {list(node_workers.keys())} and "
+                f"{n_ips} unique IP addresses {all_ips}. Please check your"
+                " network configuration. If you set `VLLM_HOST_IP` or "
+                "`HOST_IP` environment variable, make sure it is unique for"
+                " each node.")
+
         VLLM_INSTANCE_ID = get_vllm_instance_id()
 
         # Set environment variables for the driver and workers.