Questions tagged [iperf]

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Windows Server 2019 high round-trip time low transfer bandwidth

I have two Windows Servers 2019 with a round-trip time of 88 ms between them. When I try to measure bandwidth with iperf3 I get only around 16 Mbits/sec in both directions with a single stream. To get ...
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26 views

Why is iperf3 data transfer slower than scp?

I have been measuring the throughput between two hosts connected via a fiber channel. The OS is CentOS 7.9.2009 and iperf3 version is 3.1.7 (RPM). One of the tests was the measurement of transfer ...
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UDP packet won't send if it is too small

I am in an incredibly odd situation. Basically if I try to send UDP packets smaller than 1445 in size they never end up reaching their destination. I have a pretty ordinary router and a pretty ...
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1 answer
186 views

Benchmarking AWS outbound Internet bandwidth (egress) "up to 25 Gbps"

We conducted our tests on c6gn.2xlarge AWS instances located is us-east-1 region, which are advertised in AWS documentation to have a network performance of "Up to 25 Gbps" with a baseline ...
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3 votes
1 answer
154 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 ...
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1 answer
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Does Throughput calculated adds up using multiple (all active) physical adaptor

I had a network adaptor of speed 20Gbps. By stressing this adaptor using one of benchmarking tools (netperf is the tool which I used), I was able to get ~18Gbps which is well accepted. Now, after ...
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85 views

transfer file at iperf bandwidth/throughput

I need to transfer a file between 2 servers, the output of iperf is: TCP window size: 85.0 KByte (default) ------------------------------------------------------------ [ 3] local X.X.X.X port 58986 ...
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WonderShaper limits the bandwidth too much

We use WonderShaper as a traffic control tool on our linux servers. We have 10Gbit uplink, and I want to limit the upload and download to be up to 1Gbit per server. My goal is to prevent a situation ...
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iperf3 showing packetloss between 2 directly connected servers

I have 2 Dell PowerEdge-R620 servers with following configuration Processor: 2 X Intel(R) Xeon(R) CPU E5-2637 v2 @ 3.50GHz RAM: 64GB Storage: 10 SAS drives (10K RPM) with RAID 10. NIC: QUAD Ports 2 X ...
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Asymmetry in Linux VM transfer rate

I have two Linux VMs, let's call them VM1 and VM2. I have on VM1 an 80 Gb file. When I try to transfer this file from VM1 to VM2 the transfer rate is almost 256 Mb/s. scp 80Gblargefile VM2:/home/...
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iperf3 not consistent across different OS'es

I have connected two rooms via a 10Gbit fiber connection. The connection has one MikroTik switch with four SFP+ on one end (room A) and an Ubiquiti Unifi 24 ports with two SFP+ (room B). On Room A, I ...
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187 views

append date and time before each line in a text log file in windows 10

I want to append date and time before each line in a text log file in windows I run iperf command in cmd in windows 10. iperf.exe -c192.168.5.199 -u -t4 -i1 -f Kbytes -w1024k -b1024k >> client-...
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1 vote
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iPerf3 - normal and reverse measurement in the same instance

I can start a normal measurement (with 192.168.1.2 being the server) with iperf3 -c 192.168.1.2 and a reverse measurement with iperf3 -c 192.168.1.2 -R Is there any way I can do both a normal and a ...
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Getting 2g speeds on hyper-v VM through a 10g nic

I'm testing my speeds using IPERF as I've recently installed a 10G cisco switch and intel 10g NIC's on some servers to communicate with a nas server. I noticed my reads and write were awful so I've ...
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iptables tool to measure latency instead of bandwidth

I'm trying to measure the latency of having a lot of iptables rules. I tried to use iperf but I think that bandwidth is not what i want. Any help with this?
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1 vote
1 answer
307 views

FreeNAS + LAGG Slow Transfer?

I built a new file server that should be way overbuilt for its purpose. It has 2 Intel(R) Xeon(R) CPU E5-2660 v3, with 128GB of ram and it is running LCAP through an Intel X540T2 network card to a ...
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1 answer
662 views

Why is there a difference in speed of forward and reverse traffic over 10 G network in iperf tool

I have a 10G network setup between my two servers (say, Server1 and Server2) and I'm using iperf tool to measure the bandwidth of the network. Here are test cases that I performed, Test Case 1: (...
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1 answer
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variable number of lost UDP packets reported by iperf, linux scheduling?

I am testing a connectivity with an iperf server (iperf version 2.0.13 (21 Jan 2019) pthreads) running on a Bananpi M2+ single-board computer (Debian, 5.1.1-BPI-Kernel #1 SM). For different target ...
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2k views

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 ...
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1 answer
198 views

Using trickle/trickled to limit bandwidth throughput of iperf3

I'm doing some throughput testing on some radio units that have narrow channel bandwidth settings (for example sub 250KHz bandwidth). During my testing of iperf3, I noticed that the slowest speed it ...
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2 votes
2 answers
10k views

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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3 votes
1 answer
1k views

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 ...
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At Iperf3, TCP weird behavior

I am a newbie network engineer. I did a small experiment with iperf3. But I run into a small problem. (1) My question. I think TCP flow do not act properly despite of its congestion control. The flow ...
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6 votes
2 answers
25k views

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 ...
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2 votes
1 answer
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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 ...
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1 answer
300 views

Issues with Cisco IPSec VPN speed. Fast uploads, slow downloads from external to internal servers

We are using a Cisco ASA5516, configured with a IPsec (IKEv1) split tunnel VPN. When uploading files to a server behind the firewall, the transfer speeds are normal (up to 10mbps). When downloading ...
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2 votes
1 answer
1k views

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
1 answer
2k views

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 ...
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0 votes
1 answer
2k views

iperf3 UDP not reliable with iptables drop random

I'm performing some local test on my network with iperf3 using UDP connections between 2 Ubuntu 18.04 hosts. But it seems that the UDP iperf3 connections it is not robust to support a random packet ...
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1 answer
1k views

Low bandwidth when Iperfing data thorugh IPSEC tunnel

We have two server connected next to each other. When we're iperfing each other through 'simple' physical interaces - we're getting ~5GB/S of bandwidth. But when im sending traffic through tunneled (...
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1 vote
1 answer
3k views

How can I use an iperf output and only grep Interval and Bandwidth?

I am trying to get the output from the command iperf -c 10.0.0.1 -t 3600 -i 2 And only need the Interval and bandwidth fields listed for the entire hour of logging. I haven't used grep or awk in ...
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0 votes
2 answers
2k views

Undefined iperf3 ports?

I am trying to identify all of the ports affiliated with an iperf3 UDP session and am noticing that the TCP handshaking uses an undefined(?) port on the iperf3 server. Is there a way to specify all ...
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1 answer
286 views

Iperf2 capture received promiscous mode traffic Not Multicast

I want to capture all traffic in my Iperf server that I listen for promiscously, even if I am not the intended IP. I know you can do this with Multicast addresses, but I do not want to follow that ...
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1 vote
1 answer
1k views

The FastNetMon client why not show the Incoming and Outgoing traffic?

I use VMWare created two VMs on my Windows Server. two VM all are CentOS-7.2. My FastNetMon version is bellow: /opt/fastnetmon/fastnetmon --version Version: 1.1.3 master git-...
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1 vote
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675 views

I test the Iperf failed

In my Server(CentOS7.2, address is 103.193.202.2), I run the iperf server: # iperf -u -s ------------------------------------------------------------ Server listening on UDP port 5001 Receiving 1470 ...
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  • 268
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1 answer
377 views

ieprf vs iperf3 metrics does not match

I am not a network expert but I was measuring the network between to physical hosts using iperf and I got different results depending of the version I was using. Server configuration: CPU: ...
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1 vote
2 answers
684 views

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 ...
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0 votes
1 answer
93 views

Can ARP expire mid iperf connection?

If one runs an iperf connection between a node 'A' and a node 'B' is it possible that the arp entry expires from one of the nodes. [I have a simple mininet topology and while running an iperf ...
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1 vote
0 answers
2k views

Low network speed with small packets

Using iperf3 to test the network with --length 1000 --no-delay: iperf3 --interval 1 --time 3 --no-delay --length 1000 --parallel 100 --client 10.0.0.3 Result: [SUM] 0.00-3.00 sec 835 MBytes ...
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2 answers
460 views

iperf bandwidth less than interface speed

I used linux bonding driver to bond 2 NICs in mode 6 in client PC. ethtool ethX shows speed =1000 ethtool bond0 shows speed =2000 but when i use iperf bandwidth of eth0 = 934Mbps bandwidth of eth1 ...
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1 vote
1 answer
5k views

How to increase bandwidth of bonding interface in mode 6?

I am new to Linux Bonding Driver. I have configured a bond in mode 6 which combines 2 ethernet interfaces. Their individual bandwidth is 937Mbps and 700 Mbps. But when both the interfaces are up, the ...
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2 answers
2k views

What's the operation about iperf udp

I'm trying to doing some bandwidth test by run iperf on my device, My Network Max Bandwith is 100 Mbps (test by speed test CLI - https://github.com/sivel/speedtest-cli) And I ran the iperf UDP ...
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7 votes
2 answers
1k views

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 ...
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0 votes
1 answer
445 views

LACP bond work intermittently on Cisco N5000

Our clients are using Centos 7.1 and 7.3. They are two 10GB card bonded to make a 20GB link. Each of the network card is connected to a pair of Cisco N5000 switch. While running cp or iperf, I can see ...
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1 vote
0 answers
180 views

What network setting could impact iperf3 results?

I am making some bandwidth tests to set a baseline for some other tests and I have a behaviour I cannot understand. The tests are done with iperf3 on Linux (with and without -R to get both up- and ...
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2 votes
0 answers
60 views

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 ...
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1 vote
0 answers
146 views

slow single connection between two otherwise fast machines

I'm having trouble with larger file transfers from one of our virtual servers to our office network. The virtual server acts as a VPN server, therefore we call it "VPN", but the usage of VPN is not of ...
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1 vote
2 answers
22k views

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?
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0 votes
3 answers
5k views

IPERF 2.0.8/2.0.9 in Windows - "connect failed: Connection refused

I've been using iperf for some time but at present day i need to use the birectional test using -d or -r in the iperf command. The thing is that i always have "Connect failed: Connection refused" when ...
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1 vote
1 answer
5k views

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 ...
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