In a fresh Dell VxRail deployment, node discovery is orchestrated by the proprietary Loudmouth service, which natively broadcasts over the default IPv6 multicast address using VLAN 3939. If an implementation engineer explicitly alters the default port group configurations on the standard virtual switches across the ESXi hosts to utilize an alternative VLAN ID, such as 3940, the operational state of the discovery daemon is not dynamically updated.
Although the underlying esxcli commands successfully reconfigure the "Private Management Network" and
"Private VM Network" port group parameters within the hypervisor network layer, the active Loudmouth process continues to bind to the previous network state. Because the Loudmouth service was not restarted following the command executions, it fails to initialize its discovery listens and broadcasts over the newly designated VLAN 3940 interface. Consequently, the VxRail Manager cannot locate or establish communication with the nodes over the modified Top-of-Rack switch fabric. To rectify this discovery failure, the administrator must issue a service restart command directly to the Loudmouth daemon across all target nodes, ensuring that the background discovery process initializes cleanly on the updated VLAN assignment.
References: Dell VxRail Deploy Study Guide; Loudmouth Service Architecture; Node Discovery and Network Validation.