vSAN Stretched Cluster Networking Statements

AD.

A vSAN Stretched Cluster is a deployment model that spans two or more sites and provides high availability and disaster recovery capabilities. It requires a proper networking configuration to ensure that data can be replicated between the sites and that virtual machines can be migrated between them.

Here are the explanations for the two true statements:

B. The vSAN data network must communicate with the vSAN witness host.

The vSAN witness host is a virtual machine that is deployed at a third location and acts as a tie-breaker in case of a network partition between the two sites. It does not store any data but is responsible for maintaining quorum and ensuring that the vSAN cluster can continue to operate even if one site becomes unavailable. Therefore, it is essential that the vSAN data network can communicate with the vSAN witness host to ensure that it can perform its duties. This communication is typically done using Layer 3 protocols such as UDP.

D. A Stretched Cluster can use Layer 2 or Layer 3 communication for the vSAN network.

The vSAN network is responsible for replicating data between the hosts in the cluster. It can use either Layer 2 or Layer 3 communication depending on the networking configuration. A Layer 2 network extends the same broadcast domain across the sites, which can simplify the networking configuration but may also increase the risk of broadcast storms and other issues. A Layer 3 network uses routing to forward packets between the sites, which can provide better isolation and security but may require more complex configuration.

A and C are false statements because:

A. A 5ms RTT or less is required between the data sites.

The Round Trip Time (RTT) is the time it takes for a packet to travel from one site to another and back. A 5ms RTT or less is recommended but not required for a vSAN Stretched Cluster. However, a longer RTT may impact the performance of the cluster and the responsiveness of virtual machines, so it is important to consider the latency when designing the networking infrastructure.

C. PIM is required for stretched vSAN clusters.

Protocol Independent Multicast (PIM) is a Layer 3 protocol that is used for multicast communication. It is not required for a vSAN Stretched Cluster, but it can be used to optimize the replication of data between the sites. PIM can help reduce the network traffic and improve the efficiency of the vSAN network, especially in scenarios where large amounts of data need to be replicated frequently. However, PIM requires additional configuration and may not be suitable for all environments.

E is also false because:

E. A Stretched Layer 2 network is required at the vSAN data sites and at the witness site.

A Layer 2 network is not required for a vSAN Stretched Cluster, and it is up to the network administrator to choose the appropriate networking configuration. While a Layer 2 network can simplify the configuration and provide seamless connectivity between the sites, it may also introduce additional risks and limitations. A Layer 3 network can provide better isolation and security, but it may require more configuration and maintenance.