Need advise to use unicast or multicast

[Zeeshan Siddiqui]

We are going to configure Windows NLB in the DMZ for the ADFS  servers this week. We can configure the cluster in either unicast or multicast  mode. I wondered if you had a preference

http://technet.microsoft.com/en-us/library/cc782694(WS.10).aspx

Have gone through the link above and the Unicast advised looks more like broadcast.

These are blade servers that connect to HP c7000 enclosures using Cisco switches

WS-CBS3020-HPQ (12.2(50)SE

Unicast is a easier option for us as we have multiple venders running on the network and multicast could become tricky

Your advise will be much appreciated

[jbrenesj2]

Well, from a network (switching) point of view this is what can be said.

Unicast

- Each NLB cluster node replaces its real MAC address with a new one (generated by the NLB software) and  each node in the NLB cluster uses the same "virtual" MAC. Because of  this virtual MAC being used by multiple computers, a switch is not able  to learn the port for the virtual NLB cluster MAC and is forced to send  the packets destined for the NLB MAC to all ports of a switch to make  sure packets get to the right destination.

So Unicast mode = flooding on the VLAN wherehttps://supportforums.cisco.com/thread/2107897

Multicast

Same thing but since the MAC is a multicast you can statically assign it to various ports of the switch at the same time thus restricting the flooding to only there the nodes are.

Another problem here: in the router, the MAC portion of the ARP entry for the NLB address shows as incomplete so you also have to configure a static ARP entry on the router

References:

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a0080a07203.shtml

HTH, Jorge

[Zeeshan Siddiqui]

Thanks for the update

When can not add the servers to the cluster using uni cast on windows NLB.

The example config we have is for Multicast

Do we have an example for uni cast windows NLB for cisco switches ?

I have used the below config on the switch ports

switchport mode access

switch port access vlan (vlan number)