Hello there,
In unicast mode, NLB uses the NLB MAC address to replace the original hardware MAC address of each adapter in each node of the cluster and this seems to be behavior by design.
This article describes how the different Network Load Balancing (NLB) operation modes affect network infrastructure and the best ways in which the network can support each mode.
Configure network infrastructure to support the NLB operation mode https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/configure-network-to-support-nlb-operation-mode
----------------------------------------------------------------------------------------------------------------------------------------------------
--If the reply is helpful, please Upvote and Accept it as an answer–