1Network throughput in GNS3

GNS3 and especially Dynamips have never been made to get crazy performances.

However, I've recently ran some tests to identify where are the network throughput bottlenecks in GNS3 and Ithink some of the findings will be useful for some of you.

To measure the throughput, I have used iperf on one client VM or real host and one server VM with the testeddevice between these 2 elements.

Commands used

VM1 or host: iperf -c -t 30 -P 10VM2: iperf -s

Please note that everything has been run on a bare metal server i7-4770 CPU @ 3.40GHz (8 cores) with 32GB of RAM with Linux Ubuntu and using VirtualBox and Qemu using VT-x when possible. Depending on yourmachine you may achieve lower or higher throughputs.

Test results

Note that iperf has been run 3 times for each test.

Linux VM1 (VirtualBox) Dynamips c3660 router with Leopard-2FE Linux VM2 (VirtualBox)

18 Mbits/sec

18.1 Mbits/sec

18 Mbits/sec

Linux VM1 (VirtualBox) Dynamips c3660 router with NM-1FE-TX Linux VM2 (VirtualBox)

18 Mbits/sec

18 Mbits/sec

17.9 Mbits/sec

Linux VM1 (VirtualBox) Dynamips c3725 router with GT96100-FE Linux VM2 (VirtualBox)

1.15 Mbits/sec

1.12 Mbits/sec

1.15 Mbits/sec

Network throughput in GNS3

2

Using the GT96100-FE network module (default for slot0) resulted in less throughput.

Linux VM1 (VirtualBox) Dynamips c3725 router with NM-1FE-TX Linux VM2 (VirtualBox)

18 Mbits/sec

18.1 Mbits/sec

17.9 Mbits/sec

Linux VM1 (VirtualBox) Dynamips c7200 router with PA-2FE-TX Linux VM2 (VirtualBox)

17.6 Mbits/sec

17.5 Mbits/sec

17.6 Mbits/sec

Linux VM1 (VirtualBox) Dynamips c7200 router with PA-FE-TX Linux VM2 (VirtualBox)

112 Kbits/sec

106 Kbits/sec

109 Kbits/sec

Using the PA-FE-TX port adapter resulted in a extremely low throughput. I would advised against using it.

Linux VM1 (VirtualBox) Dynamips c7200 router with PA-4E Linux VM2 (VirtualBox)

18.3 Mbits/sec

18.3 Mbits/sec

18.2 Mbits/sec

Linux VM1 (VirtualBox) Dynamips c7200 router with PA-8E Linux VM2 (VirtualBox)

18.3 Mbits/sec

18.3 Mbits/sec

18.3 Mbits/sec

Linux VM1 (VirtualBox) Linux VM2 (VirtualBox)

831 Mbits/sec

942 Mbits/sec

Network throughput in GNS3

3

928 Mbits/sec

Without any surprise , VMs back to back resulted is the highest throughput.

Linux VM1 (VirtualBox) Dynamips Ethernet switch Linux VM2 (VirtualBox)

779 Mbits/sec

770 Mbits/sec

832 Mbits/sec

Linux VM1 (VirtualBox) IOU L2 switch Linux VM2 (VirtualBox)

420 Mbits/sec

426 Mbits/sec

424 Mbits/sec

Linux VM1 (VirtualBox) IOU L3 router Linux VM2 (VirtualBox)

649 Mbits/sec

655 Mbits/sec

654 Mbits/sec

IOU performances are higher that I thought.

Linux VM1 (VirtualBox) CSR1000v (VirtualBox) Linux VM2 (VirtualBox)

2.35 Mbits/sec

2.32 Mbits/sec

2.32 Mbits/sec

It is important to note that CSR1000v has 2.5 Mb/s throughput-limited trial license. These results wereexpected.

Activating the 60-day trial premium license with the "license boot level premium" command will get you a limitof 50Mb/s (you must reboot and this is valid for release Cisco IOS XE 3.12S and earlier).

47 Mbits/sec

47.1 Mbits/sec

47 Mbits/sec

Network throughput in GNS3

4

Finally, please note that with Cisco IOS XE 3.13S and later, the throughput is limited to 100 Kb/s (comparing to 2.5Mbps that has XE 3.12S and earlier), this is in demo mode - without any license. However with the AppXevaluation license you can get 10 Gb/s. Please see Cisco CSR 1000v Installation on Qemu Virtual Machine fordetails.

Linux VM1 (VirtualBox) vIOS (Qemu without KVM, e1000 NICs) Linux VM2 (VirtualBox)

2.09 Mbits/sec

2.05 Mbits/sec

2.09 Mbits/sec

It looks like vIOS has also a throughput limitation like in CSR1000v.

Linux VM1 (Qemu with KVM) vIOS (Qemu with KVM, e1000 NICs) Linux VM2 (Qemu with KVM)

2.13 Mbits/sec

2.09 Mbits/sec

2.11 Mbits/sec

It doesn't matter if you have KVM enabled or not.

Local host TAP Dynamips c3660 router with NM-1FE-TX Linux VM2 (VirtualBox)

17.9 Mbits/sec

17.9 Mbits/sec

18.0 Mbits/sec

Local host TAP Dynamips Ethernet switch Dynamips c3660 router with NM-1FE-TX Linux VM2 (VirtualBox)

18.1 Mbits/sec

18.1 Mbits/sec

18 Mbits/sec

Remote host Gigabit Ethernet NIC (nio_gen_eth in the cloud) Dynamips c3660 router withNM-1FE-TX Linux VM2 (VirtualBox)

1.54 Mbits/sec

1.09 Mbits/sec

Network throughput in GNS3

5

1.69 Mbits/sec

Interesting finding here, connecting your topology to a cloud using an Ethernet Generic NIO results in a lowthroughput.

Remote host Gigabit Ethernet NIC TAP (nio_tap in the cloud) Dynamips c3660 router withNM-1FE-TX Linux VM2 (VirtualBox)

17.9 Mbits/sec

17.8 Mbits/sec

17.9 Mbits/sec

No such problem using an TAP NIO. Note that IP forwarding was enabled to allow traffic to pass from theEthernet NIC to the TAP.

Remote host Gigabit Ethernet NIC Bridge br0 TAP (nio_tap in the cloud) Dynamipsc3660 router with NM-1FE-TX Linux VM2 (VirtualBox)

17.9 Mbits/sec

17.9 Mbits/sec

17.8 Mbits/sec

Still good using a bridge which contains the Ethernet NIC and the TAP.

Findings

Low throughputs have been identified when using the following devices:

Dynamips c7200 router with PA-FE-TX

Dynamips c3725 router with GT96100-FE

CSR1000v and IOSv are artificially limited to 2.5 Mb/s with their demo license.

IOU is faster than expected.

More interestingly throughput is low when using an Ethernet interface directly (nio_gen_eth) in GNS3 on Linux(apparently this doesn't affect Windows). Dynamips uses libpcap to attach to an Ethernet interface on Linuxand for an unknown reason it results in a lower throughput than using a TAP interface.