How to test if Jumbo Frames is configured

Quick Tip - Jumbo Frames are ethernet frames with a payload of greater than 1500 bytes MTU (Maximum Transmission Unit).   For this to work, Jumbo Frames must to configured from End to End.To quickly determine if it's configured correctly just use good ol PING.

-f  = Prevents fragmentation.

-l  = Specifies packet size.

 

Ex: ping -f -l 8972 [Destination IP]

 

How to source a ping from an IP

Quick Tip - I was troubleshooting iSCSI performance issues on a server that had NICs on the internal network, and another set of NICs on the iSCSI network.  I needed to source a ping to test connectivity of the iSCSI side.

To source a ping from a specific IP, use the following:

ping -S [SourceIP] [DestinationIP]

In my case, I had to source a ping from a specific IP and test Jumbo Frames:

 ping -S [SourceIP] -f -l 8972 [DestinationIP]

PowerCLI: How to Set the Path Selection Policy (PSP) at the host or cluster level

We recently received several new ESXi hosts in one of our datacenters.  Compellent best practices states to use the Round Robin - Path Selection Policy (PSP).  Unfortunately, the ESXi host defaults to Fixed.

The Path Selection Policy must be set at the host level for each datastore.  Soooo.... If your environment is of decent size, it's tedious and time consuming.  

The following steps will make life easier for you.

1. Get the existing configuration for your ESXi host.  Take note of the CanonicalName.

At the Host Level:
Get-VMhost myhost.mycompany.com | Get-ScsiLun -LunType disk

At the Cluster Level:
Get-Cluster mycluster | Get-VMhost | Get-scsiLun -LunType disk

2. To set the PSP, run the following command.  Enter in the appropriate CanonicalName and used the wildcard character.

At the Host Level:
Get-VMHost myhost.mycompany.com | Get-ScsiLun -CanonicalName “naa.XXX*” | Set-ScsiLun -MultipathPolicy “roundrobin”

At the Cluster Level:

Get-Cluster mycluster | Get-VMhost | Get-scsiLun -CanonicalName “naa.XXX*”| Set-ScsiLun -MultipathPolicy “roundrobin”

3. Confirm that the changes have taken place by re-running the command  in Step 1.