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Nigel-T
Contributor
Contributor

Workstation 15 - how to disable jumbo frames on lan segment

I have a couple of Linux VMs on a lan segment running on a windows host.

It appears that VMware is combining tcp frames (creating a single frame exceeding mss) which creates a problem for the application which receives raw packets from the interface.

How do I disable this behaviour?

Thanks

Nigel

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SchaalPatrick
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which Host OS, if there was enabled you can disable inside of vmware

Enable Jumbo Frames
With Workstation Player, you can enable jumbo frames for VMware virtual networks.
Jumbo frames let you send larger frames out onto the physical network or between virtual machines on
the same host.

Enable Jumbo Frames on Windows Host
With Workstation Player, you can enable jumbo frames for VMware virtual networks in the VMware Virtual
Ethernet Adapter on Windows.
Procedure
1 Navigate to Control Panel > Network and Internet > Network Connections.
2 In the Network Connections window, right-click a VMware network adapter and select Properties.
Click Configure on the Networking tab.
3 In the new window that appears, select the Advanced tab and select Jumbo Packet.
4 In the Value drop-down menu, select the packet size and click Ok.
Jumbo frame is enabled

Surce: https://sw5-prod-media-files.s3.eu-central-1.amazonaws.com/media/pdf/3d/31/4a/workstation-player-15-... 

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SchaalPatrick
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@Nigel-T 

You can also check the MTU size in Guest OS 

Info: 

  • The standard MTU is 1500 bytes. (set to <= 1500 disable)
  • When you go Jumbo Frame, the MTU is now 9,000 bytes or even more.

Check Your MTU size

Now that your network supports jumbo frames, check what your computer is set to. It’s probably 1500 bytes, since that’s the default, but it’s good to make sure.

Everything here is going to be handled with the ip command. So, use it to check the MTU size allowed by your network interfaces.

$ ip link show | grep mtu

The numbers directly after the mtu is the value you’re looking for.

Source: https://linuxconfig.org/how-to-enable-jumbo-frames-in-linux 

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Nigel-T
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Contributor

The requirement is that there should be no jumbo frames.

The MTU on the guest is default (1500).

Ethtool -k reports that all the transmit optimisations are off.

The host does not have an interface on the Lan Segment.

Wireshark on the guest shows the packets leaving with correct size.

Wireshark on a second VM on the Lan Segment shows the combined frame, with a gap in the IP.ID sequence where 2 frames have been combined.

 

 

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SchaalPatrick
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@Nigel-T 

you Report "Wireshark on a second VM on the Lan Segment shows the combined frame, with a gap in the IP.ID sequence where 2 frames have been combined." - from wich system are the "IP.ID sequence where 2 frames"?
If all Linux, windows guests has disabled Jumbo frames, you must analyze the wireshark protocol wich MAC-Adresses the sender of the combined frames are.

Q1: wich OS has second VM?
Q2: are Jumbo frames deaktivate on all NIC of second VM?
Q3: "The host does not have an interface on the Lan Segment." - Are Jumbo Frames Deaktivatet on VMWare NIC of Host?
Check settings of all "VMware Virtual Ethernet Adapter for VMnet?"
Q4: how are VM to VM connected? by Host Only? NAT? other?

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Nigel-T
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Q1: wich OS has second VM?

all VMs are Linux 


Q2: are Jumbo frames deaktivate on all NIC of second VM?

nothing has been done to enable jumbo frames anywhere in the setup.

there are multiple VMs on 4 segments, the VM that sent the combined packets is running sshd, with the ssh client generating a moderate load in order to stress the software running on other VMs which are tunnelling the data


Q3: "The host does not have an interface on the Lan Segment." - Are Jumbo Frames Deaktivatet on VMWare NIC of Host?
Check settings of all "VMware Virtual Ethernet Adapter for VMnet?"

it will next week before I can check this for all nics. I checked one which did not have jumbo activated. I suspect that the others will be the same, as I have never enabled jumbo frames anywhere.


Q4: how are VM to VM connected? by Host Only? NAT? other?

there is no NAT / DHCP (IP and MAC addresses are.manually assigned) on the segment in question, although the VMs also have a NATed / DHCP interface on to the host’s LAN

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SchaalPatrick
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SchaalPatrick_0-1649411384059.png 

SchaalPatrick_1-1649411384066.gif wila 

Could not give longer Support - All my Post will going deleted

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Nigel-T
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Does anyone know if I can control the behaviour from the VMX file?

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