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vSphere 5.5 Enhanced LACP Support Design Considerations


Simple LACP LAGBeginning with vSphere 5.1, VMware introduced LACP support on vSphere Distributed Switch (LACP v1), to form a Link Aggregation team with physical switches. LACP is a standard method (IEEE 802.3ad) to control the bundling of several physical network links together to form a logical channel for increased bandwidth and redundancy purposes.

LACP enables a network device to negotiate an automatic bundling of links by sending LACP packets (LACPDUs) to the peer. Compared to Static EtherChannel (sole possibility in vSphere ≤ 5.0), LACP has some significant benefits like failover or avoiding misconfigured and non-matching device-to-device settings.

However, that initial version of LACP support in vSphere 5.1 had some limitations, and especially the following two:

  • No benefit in regards to hashing, as the load distribution remains based on IP hash (src-dst-ip),
  • vSphere supports only one LACP group (Uplink Port Group with LACP enabled) per distributed switch and only one LACP group per host.

The latest statement is the most significant: indeed, you must enable LACP on the uplink port group…wait, so LACP will be used for all traffic of the Distributed Switch? Yes! :|

This means that you cannot override load balancing configuration for a portgroup: as I would not recommend EtherChannel/LACP for VMkernels (except for NFS, and only with a good design), this impact would imply to separate traffic types in different Distributed Switches, which may not be possible in the context (due to constraint or requirements), or undesired for manageability.

Superman bring Enhanced LACP Support to vSphere 5.5But this was for LACP v1. Enhanced LACP Support (LACP v2) on VMware vSphere 5.5 (released in september 2013) introduces a larger set of features to improve dynamic link aggregation flexibility compared with vSphere 5.1 and address the gaps with competitors.

The biggest difference into the fact that multiple LAGs can now be created on a single Distributed Switch. In vSphere 5.1, only one LAG can be created per vSphere Distributed Switch. In vSphere 5.5, up to 64 LAGs can be created per vSphere Distributed Switch.

Furthermore, another enhanced LACP feature in vSphere 5.5 is the support for all LACP load balancing types (20 different hash methods).

Enhanced LACP Support configuration

As you must have guessed, you must use the vSphere Web Client to configure Enhanced LACP. :)

First, take a look at your VDS: Enhanced LACP Support requires Distributed Switch in version 5.5.0.

vSphere 5.5 enhanced LACP support: Distributed Switch version and config

The next step is to create a new Link Aggregation Group in “Manage > Settings > LACP > New Link Aggregation Group” (via the green cross). You need to define at least a name, the number of LAG ports (24 max.), the LACP mode and the load balancing mechanism. You can create up to 64 LAGs per VDS.

vSphere 5.5 enhanced LACP support: new Link Aggregation Group

Per default, DVS is acting in Passive Mode with Normal Interval (30s). The differences between the two modes are:

  • Active – The port is in an active negotiating state, in which the port initiates negotiations with remote ports by sending LACP packets.

  • Passive – The port is in a passive negotiating state, in which the port responds to LACP packets it receives but does not initiate LACP negotiation.

Concerning the load balancing mechanism, vSphere 5.5 supports these types:

  1. Destination IP address
  2. Destination IP address and TCP/UDP port
  3. Destination IP address and VLAN
  4. Destination IP address, TCP/UDP port and VLAN
  5. Destination MAC address
  6. Destination TCP/UDP port
  7. Source IP address
  8. Source IP address and TCP/UDP port
  9. Source IP address and VLAN
  10. Source IP address, TCP/UDP port and VLAN
  11. Source MAC address
  12. Source TCP/UDP port
  13. Source and destination IP address
  14. Source and destination IP address and TCP/UDP port
  15. Source and destination IP address and VLAN
  16. Source and destination IP address, TCP/UDP port and VLAN
  17. Source and destination MAC address
  18. Source and destination TCP/UDP port
  19. Source port ID
  20. VLAN

Note: These policies are configured for a LAG.

Depending the context, you may now migrate network traffic to this new LAG, or add host to the Distributed Switch. I will not cover the details of the migration to LACP in this post, but one of the required step is to change your existing distributed portgroups configuration (or create new ones) to move the newly created LAG group to “Active Uplinks”.

The LAG is represented as an uplink like any other physical NIC and can be selected in the failover order configuration. Additionally, you can notice the warning on the load balancing drop-down menu: the load balancing policy is rendered useless by the LAG.

vSphere 5.5 enhanced LACP support: edit teaming policy on Distributed Portgroup

If you try to keep standalone uplink(s) in Active or Standby, the system will warn you and prevent you from continuing: indeed, mixing LAGs and standalone uplinks in a portgroup is not supported.