vSwitch Load Balancing – Stop Getting it Wrong!

OK, so this is one of my pet-hates.

The subject of Network Load Balancing comes up all the time when I’m visiting clients and it’s always a cause of some pain.

James’ article on Spotting The Red Flags made me think about what triggers the alarm bells ringing in the network world.

For me, if often starts with the Switch configuration, when I see something like this:

interface GigabitEthernet0/1
description ESX Server NIC0
switchport mode access
channel-group 1 mode on

Some of you might be thinking, well, there’s nothing wrong with that. In fact you’d be right. “Technically” there’s nothing wrong with that IF the vSwitch on the ESX Server is using the right load-balancing method.

BUT, it’s a red flag, because 9 times out of 10, the vSwitch configuration is using the default ‘Route based on originating port ID’ method.

And listen closely folks, as I’m not going to say it again, this method DOES NOT REQUIRE SWTICH CONFIGURATION. (Sorry for shouting, but it really, really bugs me).

There is only one ESX vSwitch load-balancing method which requires switch-side configuration and that’s ‘Route based on IP hash’.

From page 7 of the ESX Configuration Guide:

“NOTE: IP-based teaming requires that the physical switch be configured with etherchannel. For all other options, etherchannel should be disabled.”

I get even more scared when I see this:

interface GigabitEthernet0/1
description ESX Server NIC0
switchport mode access
channel-group 1 mode [auto|desirable|active|passive]

This is because any of those channel-group modes imply the use of PAgP or LACP. Let’s put an end to this debate once and for all – “VMware ESX Server does not support dynamic PAgP or LCAP.”

These dynamic link aggregation protocol are absolutely not supported on ESX, so don’t use them on the switch-side!

If you’re an ESX Admin or a Network Admin, please get together and make sure that you’re both on the same page. Time and time again, we find that there’s a disconnect between what each team thinks the other is doing.

I would strongly encourage everyone to read Ken Clien’s series of Blogs called ‘The Great vSwitch Debate‘. Especially if you’re new to the world of VMware and ESX. Part 3 focuses on the different Load Balancing methods, so check it out.

For the Network folks, this is a great reference:

VMware Infrastructure 3 in a Cisco Network Environment

For the ESX folks, these are also handy:

ESX Server host requirements for link aggregation

Sample configuration of EtherChannel / Link aggregation with ESX 3.x and Cisco/HP switches

Have a read, build some understanding and stop getting it wrong! (Please…)