I've setup lots NLB instances in lab environment. all NLB nodes are VMs which running on WIN2012R2 STD, the HOSTs are running on WIN2012R2 DC. each NLB node has two NICs, they are connected to same VLAN.
NLB mode is multicast, static ARP entry was added on L3 core switch. those NLBs have been working for a long time without any issue.
but Since Jan 2016, these NLB instances has problems almost at the same time. The NLB VIP can be reached from other subnet, but cannot be accessed within same subnet. based on the network capture on NLB node, I can't found response of ARP broadcast.
I try to enable MAC address spoofing, the NLB VIP would get available for client which from same VLAN.
my question is
1. how to resolve this issue without enable MAC spoofing?
2. what's the root Cause?
I hadn't made any changes on switch devices. except monthly windows update on server side.