diff --git a/experiments/iperf_scenario.py b/experiments/iperf_scenario.py
index f5485aa..e7f51ef 100644
--- a/experiments/iperf_scenario.py
+++ b/experiments/iperf_scenario.py
@@ -54,7 +54,7 @@ class IPerfScenario(Experiment):
         super(IPerfScenario, self).clean()
 
     def run(self):
-        self.topo.command_to(self.router, "tcpdump -i any -w router.pcap &")
+        self.topo.command_to(self.topo_config.router, "tcpdump -i any -w router.pcap &")
 
         # First run servers
         for l, s in enumerate(self.topo_config.servers):