diff --git a/backend/app/services/device_discovery.py b/backend/app/services/device_discovery.py
index 4694fdf..8a027e6 100644
--- a/backend/app/services/device_discovery.py
+++ b/backend/app/services/device_discovery.py
@@ -962,16 +962,21 @@ async def discover_via_ssh(
             )
             if ok:
                 is_slave = True
-                slave_identifier = identifier
                 slave_config_text = slave_cfg
                 master_ip_for_slave = master_host
+                # Derive slave name from master's external_id: "lane-1-1" → "lane-1-1-slave"
+                master_ext_id = next(
+                    (ext_id for ext_id, host, _ in rack_hosts if host == master_host),
+                    master_host,
+                )
+                slave_identifier = f"{master_ext_id}-slave"
                 break
 
         if not is_slave:
             logger.info(f"[ssh_discovery] {candidate_ip} — not a slave rack (no secondary linking pointing to known master)")
             continue
 
-        logger.info(f"[ssh_discovery] {candidate_ip} — SLAVE rack confirmed (identifier={slave_identifier}, master={master_ip_for_slave})")
+        logger.info(f"[ssh_discovery] {candidate_ip} — SLAVE rack confirmed (name={slave_identifier}, master={master_ip_for_slave})")
 
         # Create Rack entry for the slave in our DB
         slave_rack_id: int | None = None