Virtualization, as many say, is a journey. Some people are well down the path, while others are still beginning to understand how it works. This post is about a situation I recently came across where I had help with the understanding of how things really work.
I was performing some routine maintenance on some ESX hosts and some VM’s at one of my many jobs and noticed something a little strange.
Several of the guests had more NICs listed in the guest than vCenter reported. I took a closer look, and I couldn’t believe my eyes. One of the other admins had configured teamed NICs. Keep in mind, that these guests only utilized a single IP address, without any type of multi-homed configuration.
I thought to myself, “Teamed NICs, in a VM?” How could this be? Using VMware since Workstation 1.0, I had never seen teamed NICs inside the VM.
I had to pose the question “Why do we need teamed NIC’s in a VM?”
I got a very quick response of “For redundancy.” This response was said with a sense of authority and direction.
NIC teaming is handled by software provided by the NIC vendor, and is typically used to make two (or more) NICs appear as a single NIC.
For those familiar with VMware products, often times the NIC used in a VM, is a VMware Accelerated NIC. I wasn’t aware of any software that could do this with the VMware Accelerated NIC. Upon further examination, the VM’s were configured to use the Intel e1000 NIC, rather than the VMware Accelerated NIC.
After further investigation I found that the admin had downloaded the Intel e1000 NIC drivers, along with the teaming software, from Intel. This software package provided the ability to team the two NICs. That’s why the VM reported 3 NICs (2 e1000 + the Team).
Why did the admin team the NICs, redundancy was the answer. This was because in the traditional physical server configuration, physical NICs were always teamed in this environment, with each NIC connected to a different switch. What was missed, was that the physical NICs were already redundant at the vSwitch level.
In explaining how the vSphere configuration works, we all agreed that it wasn’t necessary to team NICs inside a VM in our configuration.
Are there any configurations that you can think of where teamed NICs would be needed?