Dell VxRail Network Planning Guide

Configure unicast for VxRail vSAN network

You can skip this task if you do not plan to use VMware vSAN as primary storage resource on the VxRail cluster.

For early versions of VxRail, multicast was required for the VMware vSAN VLAN. One or more network switches that connect to VxRail must allow the pass-through of the multicast traffic on the VMware vSAN VLAN. From VxRail 4.5.x and later, all VMware vSAN traffic replaces multicast with unicast. This change helps reduce network configuration complexity and simplifies switch configuration with unicast. Unicast is a common protocol that is enabled by default on most enterprise Ethernet switches. To configure multicast, VxRail multicast traffic for vSAN is limited to broadcast domain per vSAN VLAN. There is minimal impact on network overhead as management traffic is nominal. You can limit multicast traffic by enabling IGMP Snooping and IGMP Querier. If your switch supports, enable both IGMP Snooping, and IGMP Querier and configure this setting.

IGMP Snooping software examines IGMP protocol messages within a VLAN to discover which interfaces are connected to hosts or other devices that are interested in receiving this traffic. Using the interface information, IGMP Snooping can reduce bandwidth consumption in a multi-access LAN environment to avoid flooding an entire VLAN. IGMP Snooping tracks ports that are attached to multicast-capable routers to help manage IGMP membership report forwarding. It also responds to topology change notifications.

IGMP Querier takes care of the following:

• Sends out IGMP group membership queries at a fixed interval.
• Retrieves IGMP membership reports from active members.
• Allows updates to group membership tables.

By default, most switches enable IGMP Snooping but disable IGMP Querier. If so, you must change the settings. If IGMP Snooping is enabled, IGMP Querier must be enabled. If IGMP Snooping is disabled, IGMP Querier must be disabled.