Dears,

If Exchange 2013 CAS Windows NLB Cluster Mode is set to IGMP multicast, will  this affect Exchange operation or it is ok?

Try it and see.

Hi,

According to my knowledge and research, we need static ARP entries in your switches and use Multicast. Heres some notes for IGMP multicast:
https://technet.microsoft.com/en-us/library/cc786939(WS.10).aspx

Besides, please pay attention to below link to get more information about Selecting the Unicast or Multicast Method of Distributing Incoming Requests:
https://technet.microsoft.com/en-us/library/cc782694(v=ws.10).aspx

Thanks

I tested CAS NLB in IGMP multicast mode by pinging NLB IP from a vlan other than CAS servers vlan and it ping works fine. Also I restarted one CAS server and ping to NLB IP continues to work.

• Marked as answer by Ahmad K. Jayyusi 3 hours 48 minutes ago