Questions tagged [iperf]
The iperf tag has no usage guidance.
129
questions
13
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5
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Iperf CSV output format
If I use iperf with -y C and -r arguments to test bidirectional transfer and export it as a CSV.
I get some output but the problem is that I don't know what the column names are. For example it shows ...
- 201
12
votes
2
answers
38k
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Extreme UDP packet loss at 300Mbit (14%), but TCP > 800Mbit w/o retransmits
I have a linux box I use as the iperf3 client, testing 2 identically equipped Windows 2012 R2 server boxes with Broadcom BCM5721, 1Gb adapters (2 ports, but only 1 used for the test). All machines are ...
11
votes
3
answers
163k
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iperf connect failed: Connection refused
iperf -c 192.168.3.2 -i 2
connect failed: Connection refused
3.2 is another machine. I think the port might be blocked.
How can I make this work?
- 535
11
votes
4
answers
27k
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Packet loss rate with iperf and tcpdump
I tested a line for its link quality with iperf. The measured speed (UDP port 9005) was 96Mbps, which is fine, because both servers are connected with 100Mbps to the internet. On the other hand the ...
- 113
10
votes
3
answers
40k
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Iperf from one interface to another on the same computer?
I need to test network throughput of a server to/from itself (it's a lonnnng story!).
I love Iperf and use it across the network, but, I just can't figure out how to bind it to a single interface and ...
- 3,546
8
votes
2
answers
53k
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How to start iperf3 server in UDP mode?
I would like to test UDP connectivity with iperf3 but do not know how to start it in UDP server mode.
iperf3 -s only opens a TCP socket:
root@srv ~# lsof -i -P | grep iperf3
iperf3 21030 ...
- 3,617
7
votes
3
answers
12k
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Pre-compiled Iperf 2.x binary for win32?
I'd like to do some network testing on Windows using Iperf. The latest on sourceforge appears to be 2.0.4. However, it's only available as source to be compiled. I attempted to do some google ...
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7
votes
2
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2k
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Why multicast UDP can be slower than unicast UDP?
I have two machines (with Centos 7.3 on both) connected via 1G switch.
When I measure UDP thoughput between macines with iperf it gives about 850 Mbit/s.
However when I measure multicast UDP thoughput ...
- 173
7
votes
1
answer
821
views
Right way of measuring overlay network performance
I am currently examining the performance (especially UDP throughput) of different Docker overlay networks. I do this by creating point-to-point connections between two hosts that are connected with a ...
- 357
7
votes
1
answer
16k
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Increasing the number of outbound TCP connections
I am developing a small test client for websockets. I am using Ubuntu 11.04 . I have read
https://stackoverflow.com/questions/410616/increasing-the-maximum-number-of-tcp-ip-connections-in-linux and ...
6
votes
1
answer
4k
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iperf max udp multicast performance peaking at 10Mbit/s?
I'm trying to test UDP multicast throughput via iperf but it seems like it's not sending more than 10Mbit/s from my dev machine:
C:\> iperf -c 224.0.166.111 -u -T 1 -t 100 -i 1 -b 1000000000
------...
- 391
5
votes
4
answers
26k
views
Testing download speed using iperf
I am using iperf to test my bandwidth. But I am not getting whether it is showing my upload or download speed. Say, I have two PCs A and B. If I want to test how fast I can download a file to A from B,...
5
votes
1
answer
12k
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SSH tunnel speed is very slow
I have remote server with Ubuntu Linux and I want to establish SSH tunnel with this server from Windows machine using PuTTY(plink). I have to use this method for getting access to some service on this ...
- 105
5
votes
1
answer
14k
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ESXi 5.5, slow network speed when writing to guests
This is an issue that has been bugging me for a lot time with ESXi. I had the issue with my old Dell server (ESXi 5.0 and 5.5) and even with my new Dell T20 (ESXi 5.5).
For the current issue at hand I ...
- 93
5
votes
1
answer
1k
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Bandwidth Throttling using tc qdiscs
I am trying to limit the bandwidth between a simple iperf server and client, using a third, passive machine acting as a bridge. With no interference, iperf returns a bandwidth of ~90 Mbits/sec. My ...
- 103
4
votes
3
answers
21k
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Why is UDP slower than TCP on Ubuntu Server?
I transfer data between two Ubuntu Servers (12.04) via iperf on 1Gb LAN.
iperf -s <-> iperf -c <addr> -n2G
TCP speed = 925 Mbits/sec
iperf -su <-> iperf -uc<addr>...
- 198
4
votes
3
answers
24k
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iperf3 error - unable to create a new stream: permission denied
I am new to using iperf but others in my company use it but today it is acting strangely.
From the server:
iperf3 -s
which results in cmd showing:
Server listening on 5201.
From the client:
iperf3 --...
- 141
4
votes
2
answers
2k
views
Is it reasonably safe to host a publicly accessible iperf3 server?
CentOS 6.x
An IT team member would like run iperf3 on a publicly accessible server for the purpose of running on-demand connectivity checks from anywhere (no restrictions on remote source IP).
...
- 11.9k
4
votes
1
answer
772
views
Segmentation fault when running nuttcp inside Docker
I am measuring the UDP throughput between two Docker containers that are connected by Docker's native overlay network. I already used iperf but also want to measure the throughput with nuttcp. But ...
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4
votes
2
answers
8k
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Difference in iperf output between client and server
Been playing with iperf for the last 4 hours and I'm unable to understand why the results are different in client and server.
Consider the following iperf output on client :
iperf -c 91.121.112.163 -...
- 303
4
votes
3
answers
5k
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Different versions of iperf for windows give totally different results
Measuring TCP output from a Windows client to Solaris server:
WXP SP3 with iperf 1.7.0 --> returns an average around 90Mbit
Same client, same server but iperf 2.0.5 for windows --> returns an ...
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3
votes
1
answer
3k
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How does iperf calculate throughput and jitter?
I've read that iperf basically tries to send as much information down a connection as quickly as possible reporting on the throughput achieved. This tool is especially useful in determining the volume ...
- 223
3
votes
1
answer
4k
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using random ports with iperf/iperf3 [closed]
I am using Iperf/iperf3 -c remotehost which is
iPerf3 is a tool for active measurements of the maximum achievable bandwidth on IP networks. It supports tuning of various parameters related to ...
- 53
3
votes
1
answer
3k
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socat tun device very low throughput
I was tinkering around with socat and tried to use socat for creating a TUN device for tunneling between two debian stretch servers. However, throughput seemed very low and comparing with iperf ...
3
votes
1
answer
7k
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iperf-like bidirectional bandwidth measurement through NAT
I am using iperf to measure my uplink speed between my home PC behind NAT and a fully accessible root server. It does so using a TCP connection. For whatever reason it seems that iperf can only ...
- 1,978
3
votes
1
answer
372
views
AMD EPYC 7413 slow down to arround 400mhz when running iperf
we are trying to setup a 40gbit connection between two servers and get weird cpu behaviour when using iperf. It is also only using around 10Gbit/s of the possible 40.
Server specs:
AMD EPYC 7413
8x ...
- 71
3
votes
1
answer
1k
views
iperf 2.0.5 on Windows 7: degraded/inaccurate throughput
Was testing out some wireless equipment today using iperf on (at first) two Windows XP workstations. Throughput testing was fairly consistent at around 18Mbps.
Moved equipment around (outside), ...
- 14k
2
votes
4
answers
19k
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using Iperf3 to test upload and download
How to use Ipfer3 to test upload and download speed or in other words which data of the output given below represents upload and download speed ?
Iperf3 output
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2
votes
2
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966
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Interconnected switches Slow throughput
I am in charge of a network of which a portion of it looks like this:
One DLink DGS-1210-24 (1) as the main switch.
One DLink DGS-1210-16 (2) connected with cat5e 250 feet away connected on (1)
One ...
- 133
2
votes
1
answer
3k
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How can iperf reporting packet loss in udp
Iperf is the well known tool to calculate throughput. When i tried udp throughput using iperf on my linuxpc, It reported that 10% of packet loss.
In UDP protocol, data gram did not receice any ...
- 121
2
votes
1
answer
8k
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What's the default TCP window size of iperf3?
Does anyone know what's the default TCP window size for iperf3? It is not mentioned in the manual and I also can't find it in the output, when running a test.
- 357
2
votes
1
answer
700
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iperf3 errors and retransmissions on ESXi
When running iperf3 to test a 100G connection between a VMware ESXi box and a TrueNAS Core box, I'm seeing the following on the ESXi box:
The message "iperf3: getsockopt - Function not ...
- 451
2
votes
3
answers
2k
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Why am I only achieving 2.5Gbps over a 10Gbe direct connection between 2 machines?
I have 2 machines directly connected to each other with a 7 foot Cat6a ethernet cable (included in the box of the NIC cards). The PCIe x4 NIC I bought and in both machines is this: https://www.amazon....
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2
votes
2
answers
1k
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tcpreplay throughput on eth0 well below (iperf confirmed) max
I'm trying to replay captured UDP multicast packets at a rate of a couple of hundreds of Mbps, but it maxes out at about 86 Mbps. (For some strange reason, at other times during the day it ...
2
votes
1
answer
7k
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IPerf - Reverse test
I'm trying to perform a test using IPerf but in a special case. Usually iperf client send data to iperf server, what I need in this case is the server send data back to the client in the same ...
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2
votes
0
answers
66
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Measuring effectiveness of qdisc
I am trying to set the incoming and outgoing bandwidth of a particular interface. I set the outgoing bandwidth in the following way.
sudo tc qdisc add dev f30e888e9a857_c handle 1: root htb default ...
- 41
2
votes
1
answer
286
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Poor network performance on Server 2008 machines
I have a network consisting of about 40 Windows 7 machines (physical) and 2 servers (Virtual, ESX) which are Server 2008 Std ed (one is a SBS 2008 but they're the same 'under the hood'). Network is a ...
- 81
2
votes
0
answers
1k
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Iperf multiple streams
I need to test my network between two sites using iperf. I'd like to open parallel streams sending data on different (let's say 5 defined) ports, with random length from 10-1000, with random 1-2 ...
- 121
2
votes
2
answers
151
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File transfer - Bandwidth flickering for no reason
We are experiencing file transfer issues. I try to troubleshoot this problem but it is really hard.
Here is a screenshot I took while transferring a file from my workstation to another server. The ...
- 1,938
2
votes
2
answers
9k
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Measuring network performance between Windows and Linux
I'm using iperf to estimate network performance between Windows and Linux.
For TCP iperf shows 312 Mbits/sec from a Linux server to a Windows client, but it shows only 160 Mbits/sec from a Windows ...
- 198
1
vote
3
answers
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No package iperf3 available CentOS
I'm trying to install iperf3 on a server to run some tests...
Unfortunately I cannot. What do I need to do? Enable a repo or download a rpm file with wget?
[root@localhost hodor]# yum install iperf3
...
- 155
1
vote
2
answers
30k
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How to set the UDP Packet Size with iperf3?
How to set the UDP Packet Size with iperf3?
The flag "-M" does not work with iperf3. Is there an alternative?
- 341
1
vote
2
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4k
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Why udp has lower throughput than tcp? [duplicate]
I am measuring the tcp and udp throughput by iperf3. I run iperf3 in virtual machines, one as server and the other as client. The VMs are connecting via 10 Gbps link. The results show that tcp get ...
- 111
1
vote
1
answer
803
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iperf installation and use
I would like to use iperf to test my WAN bandwidth connection. However, I can't find a good method to install and administer it. I'm a Windows guy and don't know much about Linux, and googling iperf ...
- 483
1
vote
1
answer
3k
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Can I pull data from server to client with Iperf?
To test bandwidth, I just can push data from client to server with iperf. But can i pull data from server to client ? that is like webserver, the client request data, then server give data to client?
- 4,067
1
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2
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8k
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Command line based IP traffic generator
Does anyone know of a command line based traffic generator which can produce IP traffic so that we cant test QOS feature on DSL modem . It would be good if we can set the dscp marking in the IP ...
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1
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2
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5k
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Is iperf valid to measure network performance?
We are investigating performance issues in one of our software deployment between our application servers (Windows) and our Redis instances (Linux).
On a 10 Gbits/s link single TCP connections can ...
- 519
1
vote
2
answers
903
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How to measure bandwidth per cpu utilization [closed]
I'm trying to measure efficiency of the networking system and looking for a tool that either allows to limit max bandwidth for each test or, ideally, limit cpu utilization. At the end I need to have ...
- 131
1
vote
1
answer
5k
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Why the bandwidth is not ~10G?
I originally posted on "Network Engineering", but I was told to ask here.
I have 2 servers connected with 10G cable between them directly. I need to know that the connection is good and it has indeed ...
- 163
1
vote
2
answers
2k
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Slow local area network speeds
Updated on 2014-10-09
Disclaimer
This question is similar to Unexplained slow gigabit network speeds but because the latter is still unanswered after 5 years, and that I think I'm able to add more ...
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