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Jumbo Frames !!!!!!

-> Lets understand what’s Jumbo Frames first and how it benefits us … 

• Jumbo frames are Ethernet frames with more than 1,500 bytes of payload (MTU). Conventionally, jumbo frames can carry up to 9,000 bytes of payload.

• Jumbo Frames allow ESX Server to send larger frames out onto the physical network. The network must support Jumbo Frames end‐to‐end for Jumbo Frames to be effective.

• iSCSI with jumbo frames gives better or rather much better performance .If you are getting sluggish performance then try enabling jumbo frames 

So let’s activate it, I have used Jumbo frames only with SW initiator not HW one so if some can comment on how it works on HW it would be in for a great benefit.

Most probably you might have your VMkernel setup with 1500 MTU so we need to delete it and start over again. Its recommend to start from 0 but if you wish you can enable the jumbo frames on the fly, it won’t throw any errors.

In my case vSwitch1 was used as VMkernel for iscsi.

Step  1:
[root@esx sysconfig]# esxcfg-vswitch -d vSwitch1
Step 2:

Then I went ahead and did a listing

[root@esx sysconfig]# esxcfg-vswitch -l
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0       32          3           32                9000    vmnic0

PortGroup Name      VLAN ID  Used Ports  Uplinks
VM Network          0        0           vmnic0
Service Console     0        1           vmnic0

As it can be seen no VMkernel

Then lets start the stuff ………

Step 3:

Add a vSwitch

[root@esx sysconfig]#  esxcfg-vswitch -a vSwitch1

Step 4:

List it….
[root@esx sysconfig]#  esxcfg-vswitch -l
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0       32          3           32                9000    vmnic0
PortGroup Name      VLAN ID  Used Ports  Uplinks
VM Network          0        0           vmnic0
Service Console     0        1           vmnic0
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch1       64          1           64                1500
PortGroup Name      VLAN ID  Used Ports  Uplinks

Step 5:
Lets set the jumbo frames AKA MTU

If you wish you can execute the below command on the fly to your vSwitch without deleting it
[root@esx sysconfig]# esxcfg-vswitch -m 9000 vSwitch1
List it to see the diference
[root@esx sysconfig]#  esxcfg-vswitch -l
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0       32          3           32                9000    vmnic0
PortGroup Name      VLAN ID  Used Ports  Uplinks
VM Network          0        0           vmnic0
Service Console     0        1           vmnic0
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch1       64          1           64                9000
PortGroup Name      VLAN ID  Used Ports  Uplinks
As it can be seen MTU is now 9000 not 1500

Step 6 :
Lets assign a NIC to the newly created vSwitch
[root@esx sysconfig]# esxcfg-vswitch -L vmnic1 vSwitch1
The result
[root@esx sysconfig]# esxcfg-vswitch -l
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0       32          3           32                9000    vmnic0
PortGroup Name      VLAN ID  Used Ports  Uplinks
VM Network          0        0           vmnic0
Service Console     0        1           vmnic0
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch1       64          2           64                9000    vmnic1
PortGroup Name      VLAN ID  Used Ports  Uplinks
Step 7:
Lets give it a port group
[root@esx sysconfig]#  esxcfg-vswitch -A VMkernel vSwitch1
Step 8:

Lets see Whether we got desired output
[root@esx sysconfig]#  esxcfg-vswitch -l
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0       32          3           32                9000    vmnic0
PortGroup Name      VLAN ID  Used Ports  Uplinks
VM Network          0        0           vmnic0
Service Console     0        1           vmnic0
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch1       64          2           64                9000    vmnic1
PortGroup Name      VLAN ID  Used Ports  Uplinks
VMkernel            0        0           vmnic1
Step 9:

Now lets give it IP
[root@esx sysconfig]#  esxcfg-vmknic -a -i 192.168.0.11 -n 255.255.255.0 -m 9000 VMkernel
Hmm the output is ……..
[root@esx sysconfig]#  esxcfg-vswitch -l
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0       32          3           32                9000    vmnic0
PortGroup Name      VLAN ID  Used Ports  Uplinks
VM Network          0        0           vmnic0
Service Console     0        1           vmnic0
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch1       64          3           64                9000    vmnic1
PortGroup Name      VLAN ID  Used Ports  Uplinks
VMkernel            0        1           vmnic1
Property of vmknic
[root@esx sysconfig]#  esxcfg-vmknic -l
Interface  Port Group/DVPort   IP Family IP Address                              Netmask         Broadcast       MAC Address       MTU     TSO MSS   Enabled Type
vmk0       VMkernel            IPv4      192.168.0.11                            255.255.255.0   192.168.0.255   00:XX:83:91:23:14 9000    65535     true    STATIC

Source: http://moizzy.blogspot.com/2010/02/configure-jumbo-frames-in-esx-4-for.html