Configure port binding (for iSCSI traffic) on VMware vSphere 6.7

1.3. Associate a physical network adapter per VMkernel iSCSI port

If you go to the "Configure -> Networking -> Virtual switches" section, you will see that you have a new standard switch named "vSwitch1" with:

• 2 port groups (iSCSI Network 1 and iSCSI Network 2)
• 2 VMkernel ports (vmk1 and vmk2)
• 2 physical adapters (vmnic1 and vmnic2)

However, if you click on the name of a port group (iSCSI Network 1 or 2) or a VMkernel port (vmk1 or vmk2), you will see that the 2 physical adapters are used each time.
However, in the case of iSCSI, you can only use one physical adapter per VMkernel port. Indeed, the use of the 2 physical network cards will be managed via the port link that you configure on the software iSCSI controller of your VMware ESXi host.

To resolve this issue, click "..." to the right of the 1st port group (iSCSI Network 1), then click: Edit Settings.

Source : Configuring iSCSI port binding with multiple NICs in one vSwitch for VMware ESXi (2045040).

In the "Teaming and Failover" section of the "Edit Settings" window that appears, check the "Replace" box under "Failover order".
Next, select the physical adapter "vmnic2" and click the blue arrow going down several times to move this physical adapter to the "Unused adapters" section.

So the only active adapter for the "iSCSI Network 1" port group will be: vmnic1.

For the "iSCSI Network 2" port group, the only active adapter should be: vmnic2.

Now if you click on the name of the 1st port group (iSCSI Network 1) or 1st VMkernel port (vmk1), you will see that it will only use the 1st physical adapter (vmnic1).

If you click on the name of the 2nd port group (iSCSI Network 2) or the 1st VMkernel port (vmk2), you will see that it will only use the 2nd physical adapter (vmnic2).

If you added VMkernel adapters on your 2nd VMware ESXi host for access to your iSCSI storage, remember to do the same on this host.

So the VMkernel port "vmk1" will always use the physical adapter "vmnic1".

So the VMkernel port "vmk2" will always use the physical adapter "vmnic2".

2. Use Jumbo frames to improve performance (optional)

To improve performance for accessing your iSCSI storage, you can use Jumbo frames.
However, as specified in our tutorial "VMware ESXi 6.7 - Enable Jumbo frame support", this requires that support for Jumbo frames is available and enabled end-to-end (including on the physical switches present between your VMware ESXi hosts).

Source : Using Jumbo Frames with iSCSI - VMware Docs.

2.1. Enable Jumbo frame support on your VMware ESXi hosts

To get started, edit the settings of your new virtual switch "vSwitch1".

In the "Properties" section of the "vSwitch1 - Change Settings" window that appears, indicate an MTU of 9000 (instead of 1500 by default) and click OK.

Next, click "..." to the right of the 1st VMkernel port dedicated to iSCSI and click "Edit Settings".

In the "Port properties" section of the "Edit Settings" window that appears, specify an MTU of 9000 and click OK.

Do the same for the 2nd VMkernel port (vmk2).

Changing MTU will cause a “Lost Network Connectivity” error to appear.
You can ignore this error by clicking "Reset to Green".
Indeed, the MTU change simply caused a mini network outage when reconfiguring your standard virtual switch. But the network is still working properly.

If applicable, on your 2nd VMware ESXi host, don't forget to also set this MTU to 9000 for your standard virtual switch "vSwitch1" and for your 2 new VMkernel adapters: vmk1 and vmk2.

Again, you can ignore this “Lost Network Connectivity” error by clicking “Reset to Green”.

2.2. Enable Jumbo frame support on your physical switch

As noted previously, for Jumbo frames to be used for iSCSI traffic, the physical switch(es) through which the iSCSI traffic passes must also be configured with an MTU of 9000.
Otherwise, packets will be fragmented by your physical switch and/or network issues may occur for iSCSI traffic.

In our case, we are using VMware ESXi hosts virtualized under VMware ESXi, so the switch present between our hosts is a standard virtual switch of our physical VMware ESXi host.

2.3. Enable Jumbo frame support on your iSCSI or NAS server

To be able to use Jumbo frames for iSCSI traffic, it is also necessary that the network card of your iSCSI server or your NAS supports the use of Jumbo frames and that an MTU of 9000 is configured for them.

To get started, here is the IP configuration of our iSCSI server for iSCSI traffic:

• IP address: 10.20.0.15
• Subnet mask: 255.255.255.0.
• no default gateway, since we only use a switch for iSCSI traffic.

To enable Jumbo frame support on a Windows Server network card, right-click "Properties" on it.

Then, click on the button: Configure.

In the "Advanced" tab you should find a property regarding Jumbo frames.

In the case of a vmxnet3 network card, you will find the "Jumbo Packet" property.
Select this property and select the value "Jumbo 9000".
Then click OK.