With link aggregation control protocol (LACP) support on a vSphere Distributed Switch, you can connect ESXi hosts to physical switches by using dynamic link aggregation. You can create multiple link aggregation groups (LAGs) on a distributed switch to aggregate the bandwidth of physical NICs on ESXi hosts that are connected to LACP port channels.

Figure 1. Enhanced LACP Support on a vSphere Distributed Switch

Architecture of the LACP support on a vSphere Distributed Switch.

LACP Configuration on the Distributed Switch

You configure a LAG with two or more ports and connect physical NICs to the ports. LAG ports are teamed within the LAG, and the network traffic is load balanced between the ports through an LACP hashing algorithm. You can use a LAG to handle the traffic of distributed port groups to provide increased network bandwidth, redundancy, and load balancing to the port groups.

When you create a LAG on a distributed switch, a LAG object is also created on the proxy switch of every host that is connected to the distributed switch. For example, if you create LAG1 with two ports, LAG1 with the same number of ports is created on every host that is connected to the distributed switch.

On a host proxy switch, you can connect one physical NIC to only one LAG port. On the distributed switch, one LAG port can have multiple physical NICs from different hosts connected to it. The physical NICs on a host that you connect to the LAG ports must be connected to links that participate in an LACP port channel on the physical switch.

You can create up to 64 LAGs on a distributed switch. A host can support up to 32 LAGs. However, the number of LAGs that you can actually use depends on the capabilities of the underlying physical environment and the topology of the virtual network. For example, if the physical switch supports up to four ports in an LACP port channel, you can connect up to four physical NICs per host to a LAG.

You can configure LACP timeout value. LACP functions by sending frames down all the links that have the protocol enabled. If it finds a device on the other end of the link that also has LACP enabled, it sends frames independently along the same links, enabling the two units to detect multiple links between themselves and then combine them into a single logical link. The timeout value is the amount of time that a LAG interface waits for a Protocol Data Unit (PDU) from the remote system before bringing the LACP session down. Periodic transmissions of LACP PDUs occur at either a slow or fast transmission rate.

Port Channel Configuration on the Physical Switch

For each host on which you want to use LACP, you must create a separate LACP port channel on the physical switch. You must consider the following requirements when configuring LACP on the physical switch:

  • The number of ports in the LACP port channel must be equal to the number of physical NICs that you want to group on the host. For example, if you want to aggregate the bandwidth of two physical NICs on a host, you must create an LACP port channel with two ports on the physical switch. The LAG on the distributed switch must be configured with at least two ports.
  • The hashing algorithm of the LACP port channel on the physical switch must be the same as the hashing algorithm that is configured to the LAG on the distributed switch.
  • All physical NICs that you want to connect to the LACP port channel must be configured with the same speed and duplex.