NickNIC Teaming in vSphere 6
For a vSwitch and its associated ports or port groups to communicate with other ESXi hosts or with physical systems, the vSwitch must have at least one uplink. An uplink is a physical network adapter that is bound to the vSwitch and connected to a physical network switch. With the uplink connected to the physical network, there is connectivity for the VMkernel and the VMs connected to that vSwitch. But what happens when that physical network adapter fails, when the cable connecting that uplink to the physical network fails, or the upstream physical switch to which that uplink is connected fails? With a single uplink, network connectivity to the entire vSwitch and all of its ports or port groups is lost? This is where NIC teaming comes in.
NIC teaming involves connecting multiple physical network adapters to a single vSwitch. NIC teaming provides redundancy and load balancing of network communications to the VMkernel and VMs.
Figure 5.28 illustrates NIC teaming conceptually. Both of the vSwitches have two uplinks, and each of the uplinks connects to a different physical switch. Note that NIC teaming supports all the different connection types, so it can be used with ESXi management networking, VMkernel networking, and networking for VMs.
Figure 5.29 shows what NIC teaming looks like from within the vSphere Web Client. In this example, the vSwitch is configured with an association to multiple physical network adapters (uplinks). As mentioned previously, the ESXi host can have a maximum of 32 uplinks; these uplinks can be spread across multiple vSwitches or all tossed into a NIC team on one vSwitch. Remember that you can connect a physical NIC to only one vSwitch at a time.
Building a functional NIC team requires that all uplinks be connected to physical switches in the same broadcast domain. If VLANs are used, all the switches should be configured for VLAN trunking, and the appropriate subset of VLANs must be allowed across the VLAN trunk.
After a NIC team is established for a vSwitch, ESXi can then perform load balancing for that vSwitch. The load-balancing feature of NIC teaming does not function like the load-balancing feature of advanced routing protocols. Load balancing across a NIC team is not a product of identifying the amount of traffic transmitted through a network adapter and shifting traffic to equalize data ow through all available adapters. The load-balancing algorithm for NIC teams in a vSwitch is a balance of the number of connections—not the amount of traffic. NIC teams on a vSwitch can be configured with one of the following four load-balancing policies:
- vSwitch port-based load balancing (default)
- Source MAC-based load balancing
- IP hash-based load balancing
- Explicit failover order
The last option, explicit failover order, isn’t really a “load-balancing” policy; instead, it uses the administrator-assigned failover order whereby the highest order uplink from the list of active adapters that passes failover detection criteria is used. You’ll learn more about failover order in the section “Configuring Failover Detection and Failover Policy” later in this chapter. Also note that the list I’ve supplied here applies only to vSphere Standard Switches. I’ll cover vSphere Distributed Switches in another post.