ping works but iperf3 doesn't show any traffic for TCP

machine A has IP (eth0: 192.168.1.1, eth1: 10.10.xxx.yy) machine B has IP (eth0: 192.168.1.2)

A and B are connected through RJ5 on eth0, both sides. ping works fine on both side, but when running iperf3 on a client-server mode, it doesn't show any traffic when using TCP.

B started with the following command :

iperf3 -s

A with this :

iperf3 -B192.168.1.1 -c192.168.1.2 -n 10G -b1000M

but no connection. It timesout with 'unable to connect to server'. This happens both for TCP and UDP. iperf works for UDP, but for TCP it doesn't work with -b option. I need iperf3 as I want to test bandwidth with TCP. I am using iperf3-3.*.el6.rpm from epel. Is it broken ?

3 Answers

Do you have packet filtering enabled on machine B? What is the output of iptables -L -v on machine B? What is the output of nmap 192.168.1.2 on machine A?

For me I tried a different port and it worked, since I didn't want to mess with the iptables rules that were already on the nodes.

# iperf3 -s -p 8000
# iperf3 -c 10.0.0.2 -p 8000

You may need to add TCP port 5201 to the firewall exception on machine B.

firewall-cmd --zone=public --add-port=5201/tcp --permanent
firewall-cmd --reload