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?
There are 3 modes to Microsoft Network Load Balancing (NLB)
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
Mac address-table static 02bf.xxxx.xxxx vlan y interface
Not required – unicast mac address with unicast ip address
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
Mac address-table static 01005exx.xxxx vlan y interface
Thanks for the response. The server is actually virtualised and it is working now since they are directly connected to a 3com switch that uplinks to the nexus 5k.
This is temporary as they would be moving to the 10gb links that are directly connected to the 5k. The server network is flat and the L3 interface is the firewall not the n5k. So with this in mind should i statically add the mac address static to the 10GB interfaces alone since the microsoft server traffic will be coming from that link. Since that link will be a trunk uplink for the vmware cluster, how will this be affected. Please advise?
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