diff --git a/TestON/tests/SCPF/SCPFscaleTopo/dependencies/topo.py b/TestON/tests/SCPF/SCPFscaleTopo/dependencies/topo.py
index 4f7bfb7..22505ff 100644
--- a/TestON/tests/SCPF/SCPFscaleTopo/dependencies/topo.py
+++ b/TestON/tests/SCPF/SCPFscaleTopo/dependencies/topo.py
@@ -104,14 +104,23 @@
         send arping package from host
         return the total hosts number from Onos
     """
-    main.log.info("Sending Arping package...")
+    main.log.info( "Sending Arping package..." )
     if isinstance(hostList, list):
-        threads = []
         for h in hostList:
             main.Mininet1.arping( srcHost=h, dstHost="10.0.0.1", output=main.FALSE, noResult=True )
             time.sleep(0.5)
     else:
-        main.Mininet1.arping(srcHost=hostList)
-    summaryStr = json.loads( main.CLIs[0].summary().encode() )
-    hostNum = summaryStr.get('hosts')
+        main.Mininet1.arping( srcHost=hostList, dstHost="10.0.0.1", output=main.FALSE, noResult=True )
+    try:
+        summaryStr = ""
+        summaryStr = json.loads( main.CLIs[0].summary().encode() )
+        hostNum = summaryStr.get( 'hosts' )
+
+    except (TypeError, ValueError):
+        main.log.exception( " Object not as expected: {!r}".format( summaryStr) )
+        return -1
+    except Exception:
+        main.log.exception( self.name + ": Uncaught exception!" )
+        return -1
+
     return hostNum