We're using ESXi and I'm wondering about the "NIC Teaming" options for our vSwitches.

On a particular vSwitch with 2 NICs, is there any GOOD reason for configuring a NIC as Active and the other as Standby?. I always use Active/Active scenarios (don't see any reason for Active/Standby because if one NIC fails (and ESXi notices it) it will switch all traffic to the other NIC anyway.

Also, are there any recommendations for the VMkernel port group (or for the vSwitch it resides) as to always use Active/Standby rather than Active/Active?

Thanks! Craconia


The only thing that comes to mind is that in case of a (single) link failure, you don't lose capacity and your application becomes more predictable.

For example link usage can slowly creep up beyond a single link (application growth over months) without anyone fully realizing that. Then during a failure the application is congested and acts up, making it much more difficult to trace the source.


Don't mean to be the "well actually" guy, but...

Well actually, the most commmon reason is because each nic might go to a different switch. This is useful especially in ethernet based storage networks where redundancy is required at the host, switch, and filer levels. We are setup in exactly this way

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    You can do this just fine in active/active mode with vm port based load balancing as well as source MAC-based. The only time you need to be in the same switch (or stack) is if you use IP/hash based load balancing, which required that LAG be configured on the switch ports. – MDMarra Aug 7 '12 at 1:45

Not familiar with ESXi bonding in particular but I bet it uses Linux bonding. One of the main reasons to use Active/Backup mode is when he NIC connects to a different switch it can be more simple. In general the Active/Standby model is the most straight forward and keeps thie KISS principal. So if you don't need anywhere need the bonded bandwidth some like to just keep it simple.


One basic reason: the switch does not support Active/Active configuration.

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    VM based load balacing should be compatible with all switches. – LatinSuD Sep 25 '10 at 20:09
  • From blog.scottlowe.org/2006/12/04/… "You can most certainly create NIC teams (or “bonds”) in ESX Server without any switch support whatsoever." – user91377 Aug 11 '11 at 22:13

You might want to try to keep all communication within a single switch in normal operating conditions, so that you do not put any unneccessary load and risk congestion on a link between the switches, instead keeping the traffic within a single switch backplane. This could reduce latency and eliminate a bottleneck, depending on the way your network traffic patterns look.


I know this is an old question, but it comes up fairly high in results of a Google search on this subject, so I would like to offer a more complete set of circumstances on why you might want either configuration:

For those who want to have two connections to two switches in case of any type of failure of network equipment to have full redundancy (like me) use two ports across two NICs on the host in active/standby connection to two separate switches. If you have a cable, switch, or NIC failure, you would still have access to your host.

For those who want higher performance through an active/active link aggregation, use two ports either on two separate NICs or on the same NIC to the same Cisco switch and have the ports on the Cisco switch set up for a port channel config BEFORE you configure the connection on the host. This is complicated, and only works with Cisco switches. Do not use this unless you are either working with a Cisco certified network admin from the very beginning of planning or ARE a Cisco certified network admin and have the whole thing planned out before starting.

In either case, this is connecting a switch to two ports on a network, If you take a physical switch and connect to two ports on a network, it will cause problems, not any increased performance, unless you have certain link aggregation configuration in place.

TL;DR version:

Use Active/standby for redundancy. Preferably, go through two NICs and two switches for full redundancy.

Use active/active for performance, but make sure to work with your network admin from the beginning. Do NOT use active/active for redundancy.


Your network switch must be properly configured to use an active-active nic teaming.. in Cisco switches you need to configure a port-channel. For further information an a clear overview check this blog post: http://blog.scottlowe.org/2006/12/04/esx-server-nic-teaming-and-vlan-trunking/

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