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MTU change on vSwitch

jskfan
jskfan asked
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Last Modified: 2020-03-05
MTU change on vSwitch

If I need to change MTU on vSwitch to 2000 Bytes , then should I have to change it for the same size on Every VM Port group and every VMKernel?
For instance on vSwitch, I have VM Portgroups on VLAN 10,20,30, VMKernel  Management in VLAN 40, MKernel for vMotion in VLAN 50 , VMKernel for Storage in VLAN 60

Thank you
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Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
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Commented:
It really depends on what MTU you are running on your network, and 2000 is a very odd number!

There are a number of places you can change MTU, the vSwitch default, and then you can override this value per Portgroup.

1500 is the default for most ethernet networks, and then usually you would change to 9000 if using Jumbo Frames, useful to increase throughput for Storage Networks, iSCSI and NFS and vMotion.

BUT BUT BUT..... your entire network *MUST* also be set to the corresponding MTU value, throughout including physical switches, and end points.

So without knowing your entire network, not sure WHY you would change to a random value of 2000.

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Commented:
Some Applications may require MTU greater than 1500 Bytes
in this case, I thought if you will have to change MTU, you will change it just on the VLAN where the traffic , related to that Application, is flowing.
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
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Commented:
ALL items in the network also need to have the same MTU. (including virtual machines!).

at both sides of the network, otherwise packets will just get fragmented.

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Commented:
If Some Applications may require MTU greater than 1500 Bytes... Where can you do the change? in every   VLAN of the Network ?
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
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Commented:
on ESXi or Network switch ?

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Commented:
On ESXi
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Commented:
on the vSwitch, and on every Portgroup.

You can define an MTU on the vSwitch and this will override the MTU on all portgroups, or you can setup a custom MTU for the portgroup.

But do not change unless required.

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Commented:
Thanks

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