Sniffing the Parent Partitions Network Traffic in a Hyper-V Virtual Machine

This article discusses a situation whereby you want to monitor/mirror/sniff network port traffic on a Hyper-V Parent Partition inside on of its own child VM’s.

Why would you need to do this?

Under a traditional architecture you have the flexibility to tell your switch to mirror all traffic into or out of Port 6 onto Port 21. You then connect a laptop to Port 21 and promiscuously monitor the traffic coming into that port. Under a modern Converged/Software Defined Network architecture, this will not work.

In a modern Converged Fabric design, physical NICs are teamed. The parent partition on the hypervisor no-longer uses the physical NICs, but logically uses its own synthetic NICs for data transfers.

  1. Link Aggregation/LCAP/EtherChannel will split the traffic at the switch
  2. Teaming/LBFO will split the traffic at the hypervisor
  3. Data security will fire a red flag as you will be monitoring too much unrelated traffic
  4. If you combine them, you will overload the monitoring Port with aggregated traffic, causing performance issues and packet loss
  5. You may impact the performance of tenant VM’s and mission critical services

Fortunately the Parent Partitions own Virtual NICs are identical to the vNICs in any Hyper-V virtual machine. Consequently, you can use the same Hyper-V functionality on the Parent Partition as you would any VM.



In order to sniff traffic on the Parent Partition you must ensure the following:

  1. The Parent Partition and the VM must be connected to the same Virtual Switch
  2. The “Microsoft NDIS Capture” extension must be enabled on the Virtual Switch (this is enabled by default)
    Enable the Microsoft NDIS Capture Extensions
  3. The monitoring VM should have 2 vNICs. The vNIC used to monitor traffic should be configured onto the same VLAN as the vNIC on the Parent Partition. The monitoring NIC should have all of its service and protocol bindings disabled to ensure that only port mirrored traffic is appearing in the WireShark logs
    Disabling service and protocol bindings on the vNIC
  4. Wireshark, Microsoft NetMonitor or another promiscuous network traffic monitor
  5. If you are in a corporate environment, ensure that you have approvals from your Information Security team. In some jurisdictions port sniffing can be considered an offence


Enabling Port Sniffing

You cannot enable Port Sniffing on the Parent Partition using the Hyper-V Manager GUI. Open PowerShell on/to the Parent Partition

Execute Get-NetAdapter

Identify the name of vNIC that you will sniff traffic to/from e.g. vEthernet (Management)

Taking only the value inside the parenthesis "Management" enter the following command

Get-VMNetworkAdapter -ManagementOS 'Management' | Set-VMNetworkAdapter -PortMirroring Source

Substituting WireSharkVm for the name of your monitoring VM. Execute Get-VMNetworkAdapter 'WireSharkVm'

Identify the MAC Address of the vNIC’s that you will use to receive the Port Mirror from the Hyper-V host and enable it as the recipient for the mirror

Get-VMNetworkAdapter 'WireSharkVm' | ?{$_.MacAddress -eq '001512AB34CD'} | Set-VMNetworkAdapter -PortMirroring Destination

If the Parent Partition and VM vNICs are in the same VLAN. You should now be able to sniff traffic inbound to / outbound from the Parent Partition.


Disabling Port Sniffing

When using Port Mirroring, remember that it consumes CPU time and network resources on the hypervisor. To disable the port mirror, repeat the above commands substituting ‘None’ as the key-word for the PortMirroring parameter e.g.

Get-VMNetworkAdapter -ManagementOS 'Management' | Set-VMNetworkAdapter -PortMirroring None
Get-VMNetworkAdapter 'WireSharkVm' | ?{$_.MacAddress -eq '001512AB34CD'} | Set-VMNetworkAdapter -PortMirroring None

Powerline Comparison of Features & Functionality: Expanding your Powerline Adapter Home Network

If your home or small business has a Powerline network, there may come a time when you wish to expand your network. This could be to add wired connectivity in a different room or to a new WiFi access point. Offering better coverage for mobile and fixed wireless devices than your main router can provide.

It is not always clear from the manufacturers site which part number(s) you should buy in order to expand your existing network. Most Powerline units are sold as initial getting started kits only with little information on how to grow your network.

This Powerline Adapter Comparison attempts to simplify the options in making Powerline product choices.



The following seeks to clarify some easily misunderstood and often muddied points about Powerline.

Feature Comparison

The Powerline Comparison is divided into comparing the Powerline Adapter ranges of the six main Powerline manufacturers.

Common Questions

  1. How many adapters do I need?
  2. Can I mix and match different manufacturers adapters?
  3. I can get a 2000 Mbit/s Powerline adapter, seems like a no brainier to make my computer/Internet faster?
  4. When shouldn’t I use Powerline adapters?
  5. What should I tell my electrician if I’m having work done?

Feature Comparison: Expanding Your Network

The following table can be used to help you expand your Powerline network. For each manufacturer they show the combination of WiFi, Ethernet Port Numbers and Passthrough Port availability. Manufacturers are displayed in alphabetical order.

Passthrough: Passthrough means that there is a standard electrical socket on the front of the Powerline adapter, allowing you to plug the Powerline adapter into the wall without sacrificing access to the electrical socket for other devices.

e(#) = 1Gbps Ethernet

e(#) = 100Mbps Ethernet

(#) represents the number of Ethernet ports present on WiFi adapter modules

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1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
4 Port Ethernet
Range Max Speed Mbit/s No
Pass-through No
Pass-through No
Pass-through No
Pass-through No
AV1200 1200 PL-AC56 (802.11ac 867) e(3)
PL-E56P e(1)
AV600 600 PL-E52P e(1)
AV500 500 PL-N12 (802.11n 300) e(2)
PL-E41 e(1)
PL-X51P e(4)
AV200 200 PL-X31M e(1)


BT Powerline adapters are not internationalised and only come with UK 240v plugs.

1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through No
Pass-through No
Pass-through No
1200 1200 11ac Dual-Band Wi-fi Extender 1200 080462 (802.11ac 867) e(1)
1000 1000 Wi-Fi Home Hotspot 1000 088156 (802.11ac 583) e(1) Broadband Extender 1000 088158 e(1) Broadband Extender Flex 1000 080219 e(2)
1000 600 11ac Wi-Fi Home Hotspot Plus 1000 080461 (802.11ac 867) e(1) Mini Connector 087372 e(2)
750 750 11ac Dual-Band Wi-Fi Extender 750 85854 (802.11ac 733) e(1)
600 600 Dual-Band Wi-fi Extender 610 083530 (802.11n) e(1) Broadband Extender 600 084284 e(1) Broadband Extender Flex 600 084285 e(1)
Wi-Fi Home Hotspot Plus 600 084286 (802.11n) e(2)
Mini Wi-Fi Home Hotspot 600 084288 (802.11n) e(2)
300 300 Essentials Wi-Fi Extender 300 088159 (802.11n)


1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through No
Pass-through No
Pass-through No
AV2000 1900 DHP-701AV e(1)
AV1000 1000 DHP-W610AV (802.11ac 867) e(1) DHP-601AV e(1) DHP-P610AV e(1)
DHP-W611AV (802.11ac 867)
DHP-P601AV e(1)
AV500 500 DHP-W310AV (802.11n) e(1) DHP-P509AV e(1)
AV200 200 DHP-309AV e(1)


1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through No
Pass-through No
Pass-through No
dLAN 1200 1200 dLAN 1200+ e(1) dLAN 1200 triple+ e(3)
dLAN 1000 1000 dLAN 1000 duo+ e(2)
dLAN 650 650 dLAN 650+ e(1) dLAN 650 triple+ e(3)
dLAN 550 550 dLAN 550 duo+ e(2)
dLAN 500 500 dLAN 500 duo e(2)


1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through No
Pass-through No
Pass-through No
PL2000 2000 PLP2000 e(2)
PL1200 1200 PL1200 e(1) PLP1200 e(1)
PL1000 1000 PLW1000 e(1) (802.11n 300) PL1000 e(1) PLP1000 e(1)
PLW1000v2 e(1) (802.11n 300)
PLW1010 e(1) (802.11ac)
PLW1010v2 e(1) (802.1ac)
PL500 500 XWN5001 (802.11n 300) e(1) XAVB5101 e(1) XAVB5401 e(1) XAVB5602 e(2)
XAVB5201 e(1)
XWN5021 (802.11n 300) e(1) XAVB5221 e(1) XAVB5421 e(1)
PL200 200 XAVB1301 e(1)


1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
Range Max Speed Mbit/s No
Pass-through No
Pass-through No
Pass-through No
AV2000 2000 TL-WPA9610 (802.11ac 1200) e(1) TL-PA9020 e(2) TL-PA9020P e(2)
AV1300 1300 TL-WPA8630P (802.11ac 1350) e(1) TL-PA8010P e(1)
AV1200 1200 TL-WPA8730 (802.11ac 1750) e(3) TL-PA8010 e(1) TL-PA8030P e(3)
TL-WPA8630 (802.11ac 1200) e(3)
AV1000 1000 TL-WPA7510 (802.11ac 433) e(1) TL-PA7010 e(1) TL-PA7010P e(1) TL-PA7020 e(2) TL-PA7020P e(2)
AV600 600 TL-WPA4220 (802.11n 300) e(2) TL-PA4010 e(1) TL-PA4010P e(1) TL-PA4020P e(2)
AV500 500 TL-WPA4530 (802.11ac 433) e(3) TL-PA4010 e(1) TL-PA4020P e(2)


1 Port Ethernet
2 Port Ethernet
3 Port Ethernet
4 Port Ethernet
Range Max Speed Mbit/s No
Pass-through No
Pass-through No
Pass-through No
Pass-through No
1300 AV2 1300 TPL-430AP e(3) (802.11ac 866) TPL-422E e(1) TPL-423E e(1)
1200 AV2 1200 TPL-420E e(1) TPL-421E e(1)
500 AV 500 TPL-410AP e(2) (802.11n 300) TPL-408E e(1) TPL-407E e(1) TPL-405E e(4)
TPL-406E e(1)
TPL-401E e(1) TPL-4052E e(4)
200 AV 200 TPL-331EP e(1)

e(#) = 1Gbps Ethernet

e(#) = 100Mbps Ethernet

(#) represents the number of ethernet ports present on WiFi adapter modules

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Buying Tips & Recommendations

If you are using the Powerline Comparison to create a new or expand an existing network. The following tips may offer some guidance.

  1. If you live in a flat, apartment, communal living (e.g. Student accomodation) ony consider devices with AES encryption.
  2. When expanding your existing network consider now whather you want to start swapping out any older devices. If you do, stick to the same manufacturer, but go to their newer models. If you do not, stick to the same manufacturer and range for the best  interoperability.
  3. Wired Powerline network users should only consider new adapters with 1Gbps ethernet. The adapter should have a minimum Powerline bandwidth of 1000 Mbit/s.
  4. If you intend to create a wired network with more than two wired ethernet device connected, and will be making non-Internet file transfers (e.g. backing up to a NAS or PC to PC file copy). Only look at the 2000 Mbit/s Powerline ranges.
  5. When creating a new wireless Powerline network. Only look at the 802.11ac ranges.
  6. If your broadband Internet connection is fast (e.g. true fibre optic) ideally do not let any single part of the Powerline network be slower than your broadband connection.


Common Questions

How many adapters do I need?

It is not always clear to new users starting out with Powerline adapters that you can expand the network beyond the first two appliances that you will probably have (or will) purchased in a starter kit bundle.

Powerline is in essence a broadcast technology, meaning that it is not limited just to the first two devices that you place in your home. Neither is is necessary to operate any subsequent device that you add in a pair of devices – so you do not have to have 4,6,8 adapters live at any one time and can just as easily have 3, 5 or 7 adapters live on your network.

You do have to have more than 1 adapter however!


Can I mix and match different manufacturers adapters?

‘Powerline’ is a technical standard, not a proprietary solution to each manufacturer – although they may add proprietary innovations on top of the standard. This means that in practice you should be able to mix and match Powerline devices from different manufacturers on your network provided that the product is advertising standards compliance to the following certification combinations.

Standard Max Line
Speed (standard)
Max Client
Speed (standard)
Backwards Compatibility Notes
IEEE 1901 500 Mbit/s
IEEE 1905.1 / nVoy HomePlug n/a The standard for Powerline + Wifi devices
HomePlug 1.0 14 Mbit/s IEEE 1901
HomePlug 1.0 turbo 85 Mbit/s IEEE 1901
HomePlug AV 200 Mbit/s 80 Mbit/s IEEE 1901, HomePlug 1.0 (in theory) ‘AV’ standard for Audio/Video
HomePlug AV2 1000 Mbit/s IEEE 1901, HomePlug AV, HomePlug 1.0 (in theory)

Being standards compliant does not mean that an individual manufacturer or model of Powerline adapter will actually meet the performance levels prescribed by the standard. It also does not prevent the adapter from exceeding the standard either under conditions defined by the manufacturer.

The standard exists to ensure that if you mix your ecosystem, you can expect that under optimal conditions, the devices will operate at the speed advocated for by the standard – but not (necessarily) at the maximum capable speed of both/either device. Conversely, if you do not mix your ecosystem, and only use devices made by manufacturer x, your realised real-world performance may instead be higher than that advocated for by the standard. Consequently, it is generally recommended that where possible you stick to the same manufacturer for your Powerline network and ideally the same series/range of device.


I can get a 2000 Mbit/s Powerline adapter, seems like a no brainier to make my computer/Internet faster?

Having looked at many reviews and videos on the subject, this topic is horribly misunderstood by people ‘in the know’ to the extent that they are further confusing the issue with false information. There are 5 aspects that influence why a typical single computer/single WiFi Extender scenario isn’t in most cases going to mean a 2000 Mbit/s solution will deliver.

Electrical wiring, distribution, electrical noise and distance: The age and quality of your home electrical system will have an impact on the performance. If your electrical system isn’t up to 2000 Mbit/s, you will never see anything like that speed, possibly pulling the performance down under 100 Mbit/s. Equally, the longer the distance between the adapter termination points, the more this figure will trail off.

IEEE 802.3 (ethernet): If you are going to connect your desktop PC at one end to your router at the other (and you have modern equipment) then the Ethernet cable and the network adapters at your computer/router are only capable of a theoretical maximum of 1000 Mbit/s. Having a 2000 Mbit/s Powerline adapter will not make this point-to-point, two device network any faster even if the Powerline adapter does operate at a speed higher than 1000 Mbit/s.

IEEE 802.11 (wireless): Similarly to that of the Ethernet, wireless technology is also rated at a maximum theoretical speed 54 Mbit/s for 802.11a/g, 11 Mbit/s for 802.11b, 600Mbit/s for 802.11n and up to 3466 Mbit/s for 802.11ac – in practice it usually isn’t more than ~ 1300 Mbit/s on current generation general consumer hardware. If the WiFi Access Point module on the Powerline adapter is only capable or 600 Mbit/s or your laptop/tablet/smartphone are only capable of 600 Mbit/s, having a faster Powerline adapter will not make your wireless any faster.

Internet Connection Speed: Most home installs are probably just being used to push the Internet connection arriving at your router a little further into your property, usually because you need it to reach into another room that is out of range of the existing wireless access point. Most home internet connections (in the UK) at the current time run at sub-100 Mbit/s. Assuming that your Powerline adapter is 2000 Mbit/s, your wired desktop is 1000 Mbit/s and your tablet is 600 Mbit/s, you will not get anything faster from the Internet than the 100 Mbit/s maximum speed of your home broadband. A faster Powerline adapter can not improve the spped of your actual Internet connection to the street.

Contention: This is the most important one that people misunderstand. Powerline is what is known as a contended broadcast medium. This means that every piece of information sent to one Powerline adapter is received and processed by all of the other Powerline adapters on the network. If you have 4 Powerline adapters that try and access the network simultaneously, then the available maximum bandwidth (e.g. 2000 Mbit/s) must be shared between them. There are more sophisticated underlying technologies in newer Powerline adapters, such as OFDM and latterly MIMO that significantly help to improve this, however the key thing to understand is that the 2000 Mbit/s figure on the box is the speed available to the holistic group of all Powerline adapters on the network and must be shared amongst all termination points.

In the case of OFDM bandwidth is shared as a proportion of the total frequency spectrum available to each adapter while in the case of MIMO it is shared up to the number of available MIMO channels. For very old adapters, the full bandwidth was available, but only one Powerline adapter could communicate on the network at any one time; during which time the other adapters had to wait.

At the beginning of this section I stated that getting faster network performance it isn’t a reality in most cases. So where is it a benefit?

The benefit of having the faster line speed (the maximum theoretical bandwidth available to the group of Powerline adapters) is when there are multiple end-point devices and/or multiple Powerline adapters.

Take a scenario where Internet access is removed from the equation and pretend that there are 4 Powerline adapters, A, B, C and D. Each Powerline adapter has a single wired ethernet connection running at 1Gb/s (1000 Mbit/s). If computer A copies a file to computer B while computer C copies a file to computer D and you have 2000 Mbit/s available to the Powerline network, simplified, a 1000 Mbit/s file copy + another 1000 Mbit/s file copy (with access to MIMO) = 2000 Mbit/s. So the 2000 Mbit/s adapter will in theory allow both copies to occur at the 1Gb/s line speed (full speed).

Again, this is a theoretical figure and there are a lot of variables that will define the actual speed. In reality you may only get 800 Mbit/s during the parallel transfer (1600 Mbit/s total), but this is only achievable because the Powerline back-end is capable of supporting the higher line speed. If the Powerline network was only itself capable of 1000 Mbit/s, then the best you could have hoped for during this parallel file transfer would have been 500 Mbit/s. This is the impact of contention.

In practice, there are a lot of tweaks and optimisation’s to how OFDM, MIMO and proprietary manufacturer innovations are applied on different products. These tweaks make the examples that I have outlines significant simplifications over what may actually be going on in any given Powerline adapter. It is also true that the Powerline network will likely not run anywhere near its theoretical maximum speed, bringing down the contended bandwidth figure that you are starting out with.

In these cases a faster device with MIMO and more frequency groups available may help you to realise slightly faster speeds. It is however important to understand what the figure on the box is actually telling you -and- to set expectations (and even save money) with end users.

Simply put: If you are only looking to have a point to point link and are only ever going to be using it to access the Internet there is usually little point spending money on faster Powerline modules for your use case.


When shouldn’t I use Powerline adapters?

Powerline should not be used if:

  1. You are involved in any form of secure network or secure data workflow. Powerline can easily leak data to your neighbours or into the street. Modern adapters usually come with AES 128 encryption support as an option, however AES 128 is not the strongest form of encryption by any means here in 2018. Equally, firmware updates and patches for Powerline adapters to fix security holes are not applied automatically. Unfortunately, neither are they made available by some manufacturers as frequently as they should be.
  2. If AES Encryption technology is illegal in your country: do not use an AES enabled device.
  3. You do not have direct access to a wall socket: Powerline adapters should not be used on power gangs, PDU’s or through surge protectors. If you do, at best they will either have significant signal degradation or will not work.
  4. If the length of your internal wiring is over 300m (try and keep it far shorter than this in practice i.e. under 200m).
  5. Your house has extremely old wiring or archaic distribution / fuse boards.
  6. You want to get a good signal across multiple distribution boards / fuse boards.
  7. The electrical system has a high number of noisy appliances and you are expecting to get performance out of the system.


What should I tell my electrician if I’m having work done?

If you are having work done or want to get an electrician in to troubleshoot poor Powerline adapter performance. Offer them the following tips and get ready with a laptop, ethernet cable and a test plan (e.g., benchmark tool or a consistent large file copy).

  1. The electrician needs to provide a low-loss RF path across all circuits, and rings. The system requires low levels of electrical noise.
  2. Aluminium wiring, knob and tube wiring, old copper wiring, old fuse boards, distribution boards and sockets will undermine the performance. Unless it is 1990’s or newer, try and eliminate it from the system.
  3. Arc-Fault Circuit Interrupter (AFCI), Arc-Fault Detection Device (AFDD), Ground Fault Circuit Interrupter (GFCI), or Residual Current Device (RCD) circuit breakers can cause depleted or even entirely blocked Powerline signals. You can purchase “Powerline Compliant Outlet” surge protectors, which may mitigate some of the loss.
  4. Devices with switch-mode power supplies can create noise that limits performance. Isolate such devices before testing (especially near the receiver Powerline unit).
  5. Any appliance on your power system/ring with an electrical motor should be placed on its own surge protector e.g. air-conditioners, washing-machines and electric-fans.
  6. Remember the distance rule: Under 300m, ideally under 200m. This is especially important in the UK where rings are used allowing a run to be far longer than it might otherwise seem.
  7. 3-phase electrical systems do not work as well with Powerline. Avoid their use if possible in favour of 2-phase.
  8. If you are in a communal building, or high density residential environment, use a circuit breaker from the street to reduce the risk of data leakage out of your home.
  9. Loose screws, poor joints and thin or frayed cabling at connections can all cause problems. Ensure that everything is nice and tight.
  10. Crossing between ring mains will attenuate performance. Where possible keep adapters on the same ring main.

Netgear ReadyNAS Duo V2 and Jumbo Frames

System Requirements:

  • Netgear ReadyNAS Duo V2
  • Firmware 5.3.12
  • 9k compatible NIC’s and intermediate Layer 2/Layer 3 hardware

The Problem:

The ReadyNAS Duo V2 is a now legacy, ARM based dual 3.5″ drive SOHO NAS appliance with a single NIC and 256MB of RAM. The device was never intended to support performance or even low-end enterprise tasks.

The ReadyNAS Duo V2 is not designed for Jumbo Frames and there are no user interface entry points to enable it. It is not clear on-line whether anyone has had any actual success with enabling it. This document explores the issue.

More Info

In wanting to use the device simply as a on-line backup appliance, I wanted to try and squeeze as much performance out of it as I could. One of the obvious things to try is to enable Jumbo Frames, which allows more data to be transmitted in a single Ethernet Frame before the data has to be re-wrapped in a new header and trailer for Layer 2 transmission over an Ethernet Network. The logic being that the fewer CPU cycles being used to process the header and generate and process the CRC and footer, the faster the transfer into memory and thus the smoother the transmission of the data can occur into the disk sub-system.

In order the enable Jumbo Frames, the Maximum Transmission Unit (MTU) has to be adjusted on ALL devices in the transmission path – sender NIC, receiver NIC and any and all intermediary switch ports, bridge ports and router ports. If any one devices does not have Jumbo Frames configured to the same (or higher) value, it will fault. If you have one devices with a higher value and the other devices with a lower value, you will almost certainly see a performance reduction when transmitting from that device. Therefore: Set all of your devices to the same, common MTU values.

Depending on the manufacturer, device and driver these are usually:

Name Rounded Offset
Note: As a general rule of thumb, if you are using a PCI NIC, this is the largest MTU you can hope to achieve. PCI Express NIC’s can go up to 9k
Note: Specialist enterprise grade hardware is required for MTUs larger than 9K and these sizes are not usually available on 1Gbps NIC hardware (10 or 40Gbps hardware or higher)
Note: This is the maximum transfer size of a TCP Segment

Step 1

This was only tested on Firmware Version 5.3.12. Ensure that your firmware is up to date.

Step 2

You will need to enable Root SSH Access on the device via the official Netgear plugin. Install the plugin via the web UI and reboot the NAS before attempting to proceed.

Download: Enable Root SSH Access Plugin

Step 3

Set a static IP address on the device (or at the very least set and then unset it) to ensure that the config files have been written out correctly. It appears that a clean OS install does not make use of the interfaces file as expected until after a static IP address has been set.

Step 4

SSH into the device (using Bash, Putty for Windows or your preferred client). Usually this is root@<ipaddress>

Step 5

Perform a test to see whether Jumbo Frames currently works

ping <ipaddress> -l 8000

If you receive a successful “reply from…” then it is already working between your ReadyNAS and your PC. The expected result is however for this to fail, indicating that Jumbo Frames is not enabled

Step 6

Perform a volatile test by enabling Jumbo Frames for the session. If you lose contact with your single NIC ReadyNAS, simply reboot it to restore functionality. Under the SSH session issue the following command. If you need to set a lower Jumbo Frame value (for example 7k) change the 9000 value as appropriate.

ip link set dev eth0 mtu 9000

Step 7

Repeat the ping test from your PC

ping <ipaddress> -l 8000

This should now be successful

Step 8

If you wish to make the change permanent so that the setting persists after a restart of the ReadyNAS you must edit the interfaces file. Return to the SSH session

vi /etc/network/interfaces

In VI press i to commence insert mode

Find the entry for the eth0 interface and at the bottom of the section enter mtu 9000 (or the frame setting that you require) e.g.

iface eth0 inet static
mtu 9000

Note: That is LOWER CASE “mtu”

To save and exit VI press the Escape key and then type :wq (colon, w, q) and press return

Finally type reboot to restart the ReadyNAS

Step 9

Repeat the ping test and you should find Jumbo Frames working

Everything went wrong and now I cannot access my ReadyNAS

Don’t panic. Just access the boot menu and put it into OS Reinstall mode

  1. Turn the ReadyNAS off
  2. Use a paper clip to hold in the reset button on the back
  3. Keep the clip held in place and turn the ReadyNAS on
  4. Hold the paper clip in for 10 seconds
  5. Release the paperclip
  6. Push the backup bottom on the front of the ReadyNAS until the Disk 2 LED is the only one illuminated (be very careful that it is Disk 2 and not Disk 1. Disk 2 reinstalls the OS, Disk 1 factory resets the device and deletes all of your data)
  7. Use the paperclip one more time and single press the reset button to execute the boot menu mode
  8. Come back in 20 minutes and use RAIDar to find your ReadyNAS again (you will have to reconfigure the settings)

Does is make a difference?

Comparing the transfer speed before and afterwards does yield a significant improvement in write speed on the device.

The test configuration

The Source

  • 3.4GB ISO
  • Windows Server 2012 R2
  • From an NTFS formatted 5 disk RAID 5 array on a LSI MegaRaid 8260-8i with caching an optimisation’s enabled
  • A Quad Port Intel I350-T4 Gigabit Server NIC with Jumbo Frames set to 9014 bytes
  • Cat 5e cabling
  • 3 intermediate switches all supporting Jumbo Frames

The Destination

  • ReadyNAS firmware 5.3.12
  • Dual WD Red 3TB WD30EFRX-68AX9N0 with 64MB cache (only 5400 RPM)
  • Write caching enabled on the ReadyNAS
  • The ReadyNAS is running in Flex-RAID RAID 0

To enable write caching over SSH:

hdparm -W1 /dev/sda
hdparm -W1 /dev/sda1
hdparm -W1 /dev/sda2
hdparm -W1 /dev/sda3

Transferring the same 3.4GB ISO from the same Windows Server 2012 R2 NTFS volume over the same NIC/Network/Switches with the MTU set at the default 1500 resulted in a non-burst transfer speed of around 43MB/s (344Mbps).

Repeating the transfer with Jumbo Frames set to 9000 enabled increased this noticeably 53MB/s (424Mbps); a 18.86% increase in write speed.

Given that 53MB/s isn’t that stellar in the first place, this improvement is certainly worth having.