Microsoft NLB on Nexus 5596T

Question

  Hi guys,
We recently installed two 5596T in a cluster at a customer. They are currently migrating their servers to a VMWARE solution and have asked if the nexus supports microsoft NLB on multicast mode.
I reached to Cisco TAC on this however I havent gotten any confirmation on the commands that are required. Can you advise what commands are required for this to allow servers to see the NLB server. So far the customer are able to migrate and the solution is working however is it recommended to set static maps on the nexus for the nlb server?
Thanks much.

Answer 1

Hi,
Look this document, I applied this configuration once and worked fine.
There are 3 modes to Microsoft Network Load Balancing (NLB)
1.      1.Unicast
2.      2.Multicast
3.      3.IGMP multicast  (check the IGMP checkbox in the GUI while in multicast mode)
In general,every mode uses a different sending and receiving mac address while keeping the unicast virtual IP address (VIP) constantacross all 3 modes. This concept makes switches flood traffic at layer 2 since the switch either never sees the destination mac address come in on any of its ports(and hence can’t learn it) or the multicast mac address floods. Either multicast mode, IGMP or normal multicast, also requires static ARP entries on the gateway router since Cisco routers will not learn an ARP reply with a multicast mac address tied to a unicast ip address.
Mac addresses in the 3 modes breakdown into the following components:
The     first number in the mac address is the type of NLB configuration: 01=IGMP,     02=Unicast, 03=Multicast (Note: bit 2 is the administered locally     multicast space)
The second number, (bf) is the same for unicast and multicast mode (not IGMP multicast mode     which uses the standard 01-00-5e mac address)
The last two (IGMP multicast mode) or four (unicast or     multicast mode) numbers are the virtual IP address, i.e. c0=192, a8=168,     04=4, 0a=10 and thus the IP of 192.168.4.10 has a multicast mac address 03-BF-C0-a8-04-0a     while an IGMP multicast mac address would be 01-00-5e-7f-04-0a
Summary of configuration
NLB mode
Switch  configuration
Router  configuration
Unicast
Mac  address-table static 02bf.xxxx.xxxx vlan y interface  
Not  required – unicast mac address with unicast ip address
Multicast
Mac-address-table static 03bf.xxxx.xxxx  vlan y interface   
n7k[5.2(1)]: mac address-table  multicast 03bf.xxxx.xxxx vlan y interface
Arp  03-bh-xx-xx-xx-xx arpa
IGMP multicast
Mac address-table static 01005exx.xxxx  vlan y interface   
Arp  01-00-5e-7f-xx-xx arpa
Basicly you have to add the mac address static to all ports that you learned the mac address of your cluster microsoft (including the vpc peer-link if exist).
In the router (could be the N5K, if it doing the L3 boundary) you have to add the arp entry in the vlan sub-interface configuraton mode.
The cluster comes up instantly.
Richard