DefinIT

PowerCLI – Warning! New-VirtualSwitch without the –NumPorts parameter defaults to 56 ports!

| 28/08/2013 | Tags:

PowerCLI LogoThere’s not a lot more to say than the title of this post – if you create a new Virtual Switch using PowerCLI without specifying the NumPorts parameter, it defaults to 64 ports. This strikes me as odd when the default for a standard switch is 120.

You can see in the screenshot below that when I create a Virtual Switch without the parameter, it creates it with 64 ports. Once you minus the 8 reserved for physical NIC ports (uplinks), CDP traffic, and network discovery it leaves you with 56 ports available for VMs.

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Obviously this isn’t something that everyone will run into, 56 VMs on a host is a high consolidation ratio! But it caught us out this week with Virtual Machines and some weird network problems! Since changing a vSwitch’s number of ports requires a reboot I’ll be migrating these to a Distributed Switch (which I should have done a while ago anyway!) which will fix the problem with zero further downtime.