Wednesday, June 26, 2013

Microsoft Network Load Balancing, and how to make it work with a Cisco Nexus

Microsoft Network Load Balancing has one or two “interesting” issues due to the way it does networking.  More specifically, it utilises a Multicast MAC address with a Unicast IP address.  Someone much smarter than me explains the ins and outs of the issue here

This issue manifests itself in that clients outside of the cluster’s LAN cannot connect to the IP.

Now that we understand the issue,  how do we resolve it?  The fixes listed in the article are all valid, however we can get this working by tweaking the config on our Nexus.

interface Vlan10
  no ip redirects
  ip address 192.168.10.1/24
  ip arp 192.168.10.100 03BF.0A03.00CF
  description Server Farm
  no shutdown

Your clients should now be able connect to the cluster IP address without issue.