So today I learned a valuable lesson with cisco switches and wNLB. They don’t get along together! The MAC Address for the wNLB IP doesn’t get registered with the cisco switches so they will have a hard time routing. To fix this you have to create a static ARP entry for the MAC address of the wNLB IP that points to the wNLB IP.


Server 1 

  1. NIC IP –
  2. MAC – 00-00-00-00-00-00-00-01

Server 2

  1. NIC IP –
  2. MAC – 00-00-00-00-00-00-00-02

Clustered IP

  2. MAC – 00-00-00-00-00-00-00-03


Each NIC will have its own MAC address even the virtual IP. You have to flush the ARP cache in the cisco switch and manually enter the MAC Address

  1. Log into cisco switch
  2. Enter privileged mode
  3. Type – arp 00-00-00-00-00-00-00-03
  4. Save running config to startup 
  5. Test it out