iSCSI and Jumbo Frames configuration on VMware ESXi host

Products

• VMware vSphere ESXi

Issue/Introduction

This article provides information on setting up a NAS and an iSCSI environment with Jumbo Frames.

Symptoms:

• You see large queues when monitoring Jumbo Frames.
• You observe packet fragmentation when viewing a packet capture using the tcpdump utility.

Environment

VMware vSphere 7.0.x
VMware vSphere 8.0.x

Resolution

Ensure that you read this important information about Jumbo Frames before working with them:

• ESX/ESXi supports a maximum MTU size of 9000.
  
  Note: Some switch configurations for Jumbo Frames need to have an MTU set higher than 9000. For more information, see the https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/CLIConfigurationGuide/QoS.html
  
  
  
• Any packet larger than 1500 MTU is a Jumbo Frame. ESX/ESXi supports frames up to 9000 Bytes.
• It is possible to configure Jumbo Frames for an iSCSI network.
• You can enable Jumbo Frames for each vSwitch or VMkernel interface through the command line interface on your ESX host.
• To allow an ESX host to send larger frames out onto the physical network, the network must support Jumbo Frames end to end.
• Ensure that your NIC or LOM supports Jumbo Frames.

To enable Jumbo Frames for independent hardware iSCSI adapters in the vSphere Web Client, change the default value of the MTU parameter:

 

Use the Advanced Options settings to change the MTU parameter for the iSCSI HBA.

1. Browse to the host in the vSphere Web Client navigator.
2. Click the Manage tab.
3. Click Storage.
4. Click Storage Adapters, and select the independent hardware iSCSI adapter from the list of adapters.
5. Under Adapter Details, click the Advanced Options tab.
6. Click Edit.
7. Change the value of the MTU parameter.

 

Configuring Jumbo Frames on a vSphere Standard Switch

To configure Jumbo Frames on a vSphere Standard Switch:

1. Log in to the vSphere Client.
2. Select the Hosts and Clusters inventory view.
3. Under the host Configuration tab, click Networking.
4. Click Properties for the vSphere standard switch associated with the VMkernel to modify.
5. Under the Ports tab, select the VMkernel interface.
6. Click Edit.
7. Set the MTU parameter to 9000.
8. Click OK.

Note: To create a Jumbo Frames-enabled vNetwork Distributed Switch and its associated VMkernel interfaces, see Enabling Jumbo Frames for VMkernel ports in a virtual distributed switch (324494)

To create a Jumbo Frames-enabled VMkernel interface on a vNetwork Standard Switch:

1. Log directly in to the ESX host console.
2. Obtain the current vSwitch and portgroup configuration with the esxcfg-vswitch command:
   
   # esxcfg-vswitch -l
   
   
3. To create a VMkernel interface with Jumbo Frames support, you must first create a portgroup on an existing vSwitch:
   
   # esxcfg-vswitch -A vmkernel_port_group_namevSwitch#
   
   Example:
   
   # esxcfg-vswitch -A iSCSI vSwitch2
   
   Note: If you plan to have a vSwitch that contains only the iSCSI port group, you can specify the MTU for the vSwitch to be 9000 and must specify an MTU of 9000 when creating the VMkernel port as well in the next step. To configure a vSwitch to use Jumbo Frames (MTU 9000):
   
   # esxcfg-vswitch -m 9000 vSwitch#
   
   Example:
   
   # esxcfg-vswitch -m 9000 vSwitch2
   
   
4. To create a VMkernel connection with Jumbo Frame support:
   
   
   • Run this command
     
     # esxcli network ip interface set -m 9000 -i vmk_interface
     
     Example:
     
     # esxcli network ip interface set -m 9000 -i vmk1
     
     
5. To display a list of VMkernel interfaces, and to check that the configuration of the Jumbo Frame‐enabled interface is correct:
   
   
   • Run this command 
     
     # esxcli network ip interface list
     
     

Additional Information

For related information, see

Enabling Jumbo Frames on virtual distributed switches
Configuração de iSCSI e Jumbo Frames em ESX/ESXi