This Knowledge Base article provides information about configuring the SolarWinds Channel and explains why the SolarWinds Channel cannot be configured to use the same subnet as the Principal (Public) NIC's
The SolarWinds Channel is used to transmit heartbeat "Yes I'm alive" messages between the primary and secondary servers and replication traffic from the active server to the passive server. If the SolarWinds Channel were configured to use the same subnet as the Principal (Public) network, production traffic would be impacted thereby causing reduced throughput on the Principal (Public) network.
SolarWinds Orion Failover Engine prerequisites require that the SolarWinds Channel be configured on a separate subnet from the Principal (Public) subnet to allow maximum throughput via the SolarWinds Channel and production Principal (Public) network.
SolarWinds Orion Failover Engine All Versions