Re: vSwitch - Unicast - MS NLB

Notes:

• VMware recommends configuring the cluster to use NLB multicast mode even though NLB unicast mode should function correctly if you complete these steps. This recommendation is based on the possibility that the settings described in these steps might affect vMotion operations on virtual machines. Also, unicast mode forces the physical switches on the LAN to broadcast all NLB cluster traffic to every machine on the LAN. If you plan to use NLB unicast mode, ensure that:
  
  
  
  • All members of the NLB cluster must be running on the same ESXi/ESX host.
    
  • All members of the NLB cluster must be connected to a single portgroup on the virtual switch.
    
  • vMotion for unicast NLB virtual machines is not supported (unless you want to migrate all NLB members to a different ESXi/ESX host).
    
  • The Security Policy Forged Transmit on the Portgroup is set to Accept.
    
  • The transmission of RARP packets is prevented on the portgroup / virtual switch as explained in the later part of the article.
    
• VMware recommends having two NICs on the NLB server.
  

Notes:

• ESXi/ESX vSwitch properties Notify Switches = NO
  
• Unicast mode reassigns the station (MAC) address of the network adapter for which it is enabled and all cluster hosts are assigned the same MAC (media access control) address, you cannot have ESXi/ESX send ARP or RARP to update the physical switch port with the actual MAC address of the NICs as this break the the unicast NLB communication
  
• ESXi/ESX vSwitch security properties must be set to default, Forged Transmits = Accept.
  
• 
  

Requirements and notes for setting up NLB unicast mode:

• Two machines running Windows Server 2003 or later
  
• Each machine should have at least two network cards and at least one fixed IP address
  
• VMware recommends two adapters in each machine for best performance
  
• One adapter mapped to the real IP address (Microsoft calls this the Dedicated IP), and one mapped to the virtual IP address (Microsoft calls this the Cluster IP)
  
• A second network card is required for communication between the servers
  

are you sure that you have followed all the above things... and did you checked any settings limited to unicast in physical switch