Network path redundancy between cluster nodes is important for vSphere HA reliability. A single management network ends up being a single point of failure and can result in failovers although only the network has failed.
If you have only one management network, any failure between the host and the cluster can cause an unnecessary (or false) failover activity if heartbeat datastore connectivity is not retained during the networking failure. Possible failures include NIC failures, network cable failures, network cable removal, and switch resets. Consider these possible sources of failure between hosts and try to minimize them, typically by providing network redundancy.
You can implement network redundancy at the NIC level with NIC teaming, or at the management network level. In most implementations, NIC teaming provides sufficient redundancy, but you can use or add management network redundancy if required. Redundant management networking allows the reliable detection of failures and prevents isolation or partition conditions from occurring, because heartbeats can be sent over multiple networks.
Configure the fewest possible number of hardware segments between the servers in a cluster. The goal being to limit single points of failure. Additionally, routes with too many hops can cause networking packet delays for heartbeats, and increase the possible points of failure.
Network Redundancy Using NIC Teaming
Using a team of two NICs connected to separate physical switches improves the reliability of a management network. Because servers connected through two NICs (and through separate switches) have two independent paths for sending and receiving heartbeats, the cluster is more resilient. To configure a NIC team for the management network, configure the vNICs in vSwitch configuration for Active or Standby configuration. The recommended parameter settings for the vNICs are:
- Default load balancing = route based on originating port ID
- Failback = No
After you have added a NIC to a host in your vSphere HA cluster, you must reconfigure vSphere HA on that host.
Network Redundancy Using a Second Network
As an alternative to NIC teaming for providing redundancy for heartbeats, you can create a second management network connection, which is attached to a separate virtual switch. The original management network connection is used for network and management purposes. When the second management network connection is created, vSphere HA sends heartbeats over both management network connections. If one path fails, vSphere HA still sends and receives heartbeats over the other path.