NIC Teaming Policies in VMware vSphere

The first point of interest is the load-balancing policy. This is basically how we tell the vSwitch to handle outbound traffic, and there are four choices on a standard vSwitch:

1. Route based on the originating virtual port
2. Route based on IP hash
3. Route based on source MAC hash
4. Use explicit failover order

Keep in mind that we’re not concerned with the inbound traffic because that’s not within our control. Traffic arrives on whatever uplink the upstream switch decided to put it on, and the vSwitch is only responsible for making sure it reaches its destination.

The first option, route based on the originating virtual port, is the default selection for a new vSwitch. Every VM and VMkernel port on a vSwitch is connected to a virtual port. When the vSwitch receives traffic from either of these objects, it assigns the virtual port an uplink and uses it for traffic. The chosen uplink will typically not change unless there is an uplink failure, the VM changes power state, or the VM is migrated around via vMotion.

The second option, route based on IP hash, is used in conjunction with a link aggregation group (LAG), also called an EtherChannel or port channel. When traffic enters the vSwitch, the load-balancing policy will create a hash value of the source and destination IP addresses in the packet. The resulting hash value dictates which uplink will be used.

The third option, route based on source MAC hash, is similar to the IP hash idea, except the policy examines only the source MAC address in the Ethernet frame. To be honest, we have rarely seen this policy used in a production environment, but it can be handy for a nested hypervisor VM to help balance its nested VM traffic over multiple uplinks.

The fourth and final option, use explicit failover order, really doesn’t do any sort of load balancing. Instead, the first Active NIC on the list is used. If that one fails, the next Active NIC on the list is used, and so on, until you reach the Standby NICs. Keep in mind that if you select the Explicit Failover option and you have a vSwitch with many uplinks, only one of them will be actively used at any given time. Use this policy only in circumstances where using only one link rather than load balancing over all links is desired or required.

Credit for this info goes to "Networking for VMware Administrators"

NOTE

In almost all cases, the route based on the originating virtual port is more than adequate. Don’t try to get fancy with an exotic load-balancing policy unless you see an issue where the majority of traffic is being sent down the same uplink and other uplinks are relatively quiet. Remember our motto—the simplest designs are almost always the best designs.

A single VM will not be able to take advantage of more than a single uplink in most circumstances. If you provide a pair of 1 Gb Ethernet uplinks to your vSwitch, a VM will still only use one of those uplinks at a time. There are exceptions to this concept, such as when a VM has multiple virtual NICs attached on a vSwitch with IP hash, but are relatively rare to see in production environments.