Q and A: I only have two NICs on my Hyper-V host. Should I team them or not?

Question via e-mail:

I am using blade servers for my Hyper-V cluster and I can only have two NICs per blade in this configuration.

I am considering two options on how to configure the NICs:

1)      Use one NIC for internal network and one NIC for external network, connected to the virtual switch
2)      Team the two NICs together and use the same path for all kinds of traffic

What would you recommend?


If you’re using clusters, I assume you’re concerned with high availability and network fault tolerance. In this case using one NIC for each kind of traffic creates two single points of failure. You should avoid that.

I would recommend that you team the two NICs, connect the team to the virtual switch and add a few virtual NICs to the parent partition for you storage, migration, cluster and management traffic. You can then use QoS policies manage your quality of service.

If you’re using SMB for storage, be sure to have multiple vNICs (one for each physical NIC behind the team), so you can properly leverage SMB Multichannel in combination with NIC teaming. By the way, SMB Direct (RDMA) won’t work with this scenario.

The first thing you want to do is create a team out of the two NICs and connect the team to a Hyper-V virtual switch. For instance:

New-NetLbfoTeam Team1 –TeamMembers NIC1, NIC2 –TeamNicName TeamNIC1
New-VMSwitch TeamSwitch –NetAdapterName TeamNIC1 –MinimumBandwidthMode Weight –AllowManagementOS $false

Next, you want to create multiple vNICs on the parent partition, one for each kind of traffic (two for SMB). Here’s an example:

Add-VMNetworkAdapter –ManagementOS –Name SMB1 –SwitchName TeamSwitch
Add-VMNetworkAdapter –ManagementOS –Name SMB2 –SwitchName TeamSwitch
Add-VMNetworkAdapter –ManagementOS –Name Migration –SwitchName TeamSwitch
Add-VMNetworkAdapter –ManagementOS –Name Cluster –SwitchName TeamSwitch
Add-VMNetworkAdapter –ManagementOS –Name Management –SwitchName TeamSwitch

After this, you want to configure the NICs properly. This will include setting IP addresses, creating separate subnets for each kind of traffic. You can optionally put them each on a different VLAN.

Since you have lots of NICs now and you’re already in manual configuration territory anyway, you might want to help the SMB Multichannel by pointing it to the NICs that should be used by SMB. You can do this by configuring SMB Multichannel constraints instead of letting SMB try all different paths. For instance, assuming that your Scale-Out File Server name is SOFS, you could use:

New-SmbMultichannelConstraint -ServerName SOFS -InterfaceAlias SMB1, SMB2

Last but not least you might also want set QoS for each kind of traffic, using the facilities provided by the Hyper-V virtual switch. One way to do it is:

Set-VMNetworkAdapter –ManagementOS –Name SMB1 –MinimumBandwidthWeight 20
Set-VMNetworkAdapter –ManagementOS –Name SMB2 –MinimumBandwidthWeight 20
Set-VMNetworkAdapter –ManagementOS –Name Migration –MinimumBandwidthWeight 20
Set-VMNetworkAdapter –ManagementOS –Name Cluster –MinimumBandwidthWeight 5
Set-VMNetworkAdapter –ManagementOS –Name Management –MinimumBandwidthWeight 5
Set-VMNetworkAdapter –VMName * -MinimumBandwidthWeight 1

There is a great TechNet page with details on this and other network configurations at http://technet.microsoft.com/en-us/library/jj735302.aspx

Comments (2)

  1. Great article, thanks, Jose.

  2. uri says:

    in the command mentioned:
    New-VMSwitch TeamSwitch –NetAdapterName TeamNIC1 –MinimumBandwidthMode Weight –AllowManagementOS $false

    shouldn’t the AllowManagementOS be set to $true?