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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. A single management network ends up being a single point of failure and can result in failovers although only the network has failed. Network path redundancy between cluster nodes is important for vSphere HA reliability. Use the das.isolationaddress advanced option to add isolation addresses for additional networks. Only one default gateway is specified, regardless of how many management networks have been defined. However, if the host cannot ping its isolation address, it is likely that the host has become isolated from the network and no failover action is taken.īy default, the network isolation address is the default gateway for the host. If a host can ping its network isolation address, the host is not network isolated, and the other hosts in the cluster have either failed or are network partitioned. This address is pinged only when a host has stopped receiving heartbeats from all other hosts in the cluster. Network Isolation AddressesĪ network isolation address is an IP address that is pinged to determine whether a host is isolated from the network. Therefore, to ensure network flow separation, the vmkNICs used by vSphere HA and by other features must be on different subnets. vSphere HA agents send packets using any pNIC that is associated with a given subnet when there is also at least one vmkNIC configured for vSphere HA management traffic. To keep vSphere HA agent traffic on the networks you have specified, configure hosts so vmkNICs used by vSphere HA do not share subnets with vmkNICs used for other purposes. With an ESXi host, if you want to use a network other than the one vCenter Server uses to communicate with the host for vSphere HA, you must explicitly enable the Management traffic check box.

On ESXi hosts in the cluster, vSphere HA communications, by default, travel over VMkernel networks.

To contain vSphere HA traffic to a subset of the ESX console networks, use the allowedNetworks advanced option.

VMkernel networks are not used by these hosts for vSphere HA communications.

On legacy ESX hosts in the cluster, vSphere HA communications travel over all networks that are designated as service console networks.

To identify which network operations might disrupt the functioning of vSphere HA, you must know which management networks are being used for heart beating and other vSphere HA communications. Networks Used for vSphere HA Communications Note: Because networking is a vital component of vSphere HA, if network maintenance must be performed inform the vSphere HA administrator. After you have made the networking configuration changes, you must reconfigure vSphere HA on all hosts in the cluster, which causes the network information to be reinspected.

When you change the networking configuration on the ESXi hosts themselves, for example, adding port groups, or removing vSwitches, suspend Host Monitoring.

Changing your network hardware or networking settings can interrupt the heartbeats that vSphere HA uses to detect host failures, which might result in unwanted attempts to fail over virtual machines. When changing the networks that your clustered ESXi hosts are on, suspend the Host Monitoring feature.The following network maintenance suggestions can help you avoid the accidental detection of failed hosts and network isolation because of dropped vSphere HA heartbeats.

Best Practices include recommendations for your ESXi hosts, and for cabling, switches, routers, and firewalls. Observe the following best practices for the configuration of host NICs and network topology for vSphere HA.