Tags
7010, ccie data center, cisco, data center, Fryguy, fryguy_pa, nexus, nexus 7000, nexus 7010, nexus 7018, nlb, nxos
Oh the joys of Microsoft Network Load Balancing (NLB). One of the wonderful ways that it is usually configured is using a Multicast MAC address utilizing a Unicast IP address. Needless to say, most network devices do not like that and thus have problems when devices outside the local LAN attempt to connect to the NLB address. In order to work around this problem you need to configure a static ARP entry on the gateway so that the devices know how to get to the server.
On IOS, this is not so hard as you configure the a static ARP entry (arp 10.1.1.99 0300.5e11.1111). That command there on the gateway will usually get things working. You may also need to define where that MAC address lives – and the command to do that would be mac-address-table static 0300.5e11.1111 vlan 200 interface fa2/3 fa2/4 This information was obtained from a Cisco document can be found here if you need more information – http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a0080a07203.shtml
Now, on the NX-OS it is a little different as you need to configure the static ARP entry under the VLAN interface in order for it to work:
interface Vlan100
no shutdown
description [—-[ Standard VM VLAN ]—-]
no ip redirects
ip address 10.1.1.2/24
ip arp 10.1.1.99 0300.5e11.1111
N7K1# sh ip arp | inc 1111
10.1.1.99 – 0300.5e11.1111 Vlan100
Does it matter what method of NLB i am using , unicast or multicast ? the method i am using is multicast but the mac address i am getting from the cluster is unicast : 03bf.ac13.20c9 . I have a 6509 as a layer2 switch and nexus 7k is the gateway.
Thanks .
That is the problem we have also, it is a multicast mac to a unicast address. If you do the static ARP on the gateway it should fix it. You may also need to do it on the switch (depending on mac/port configuration) – but I think the gateway should be sufficient.
Commenting on microsoft nlb multicast mode mac address is the format 03-BF-0A-XX-XX-XX Where xx just mapped to last 3 octet of the ip address . On nexus side if I use igmp multicast mode which maps the multicast mac to 01-00-5E Format but I could not put the static arp on Nexus 7K ,it gave me error that you can not put the static entry for multicast address . I could enter 03-BF-0A though.