Unicast Microsoft (NLB) mode support on Nexus 9000 switches

[faizan.khan]

We Want Cisco's help to confirm that if this will work.

  BIOS: version 07.41

  NXOS: version 7.0 (3) I2 (2d)

  BIOS compile time: 10/12/2015

  NXOS image file is: bootflash: ///nxos.7.0.3.I2.2d.bin

 NXOS compile time: 4/24/2016 13:00:00 [04/24/2016 22:28:19]

We will move trunks to 2 Nexus 9396, the servers are available in 2 HP switches.

What we fear is that Microsoft NLB will not work when moving, given the "Design Considerations" below.

Or does it work in our version?

So, what does Cisco recommend how to configure Microsoft NLB, is multicast or unicast mode?

We intended to try with unicast NLB, and then it says this:

Design Considerations:

With these static entries in place, you must account for these designs considerations:

"All NLB cluster members must be reachable via the same port-channel / physical interface from the perspective of the Nexus 9000.

"The ability to adapt to change in the physical location of the NLB cluster members, due to vMotion, is not possible without an appropriate design.

https://www.cisco.com/c/en/us/support/docs/switches/nexus-9000-series-switches/118951-config-nexus9000-unicast-nlb-00.html

[faizan.khan · Accepted solution]

Nexus 9396 (NX-OS) only supports Microsoft NLB in unicast mode by statically configuring an ARP entry for the NLB cluster. In the example, this is 200.200.200.200 / c8c8.c8c8.c8c8.

https://www.cisco.com/c/en/us/support/docs/switches/nexus-9000-series-switches/118951-config-nexus9000-unicast-nlb-00.html

The letter "All NLB cluster members must be reachable via the same port-channel / physical interface from the perspective of the Nexus 9000.": Means that all cluster members (ie, clusters with cluster IP 200.200.200.200.2005) must sit behind Po3 (ie. behind a logical / physically outgoing interface from the Nexus pair perspective). If there are more cluster members then they need to be connected to the switch that is connected with the Po3 to the Nexus pair. Of course, this can be a switch pair running MLAG (vPC) against N9396-1 and N9396-2. It is strongly recommended to prune a VLAN 200 to minimize the impact that NLB has in unicast mode (when it uses flooding).

Alternative:
1. Look at the Nexus 9300-EX or later. The platform also supports NLB in Multicast mode which is better than driving in unicast.
2. Evaluate if ITD (Intelligent Traffic Director) could fit. This is a built-in load balancing function in the NX-OS. Supports for IPv4 in Nexus 9396. Requires a Network Services license. Attached are examples of how ITD can replace NLB.