Heartbeat Network – Original Posted Feb 10, 2005

This is pet peeve of mine. I have run into several instances where clusters have been installed and the heartbeat network is not properly configured. The heartbeat network is a private network shared just by the nodes of a cluster and is not accessible to other systems. It is not supposed to be routable at all. When it is built, you should select the option for "Internal cluster communications only (private network)" for the private heartbeat network. Selecting anything else can be a problem since this network is not routable and can’t connect to other networks. Make sure that you use IP addresses for your heartbeat network that do not exist anywhere else in your network or on the Internet.

You basically have a few choices when it comes to building the private heartbeat network:

  1. Use a cross over cable between the nodes (only valid for two node clusters)
  2. Use a VLAN on a switch
  3. Use a dedicated switch
  4. Use a dedicated hub

I highly recommend using a dedicated hub over a switch for a couple of very good reasons.

  • Power problems can cause the loss of the switch configuration. I have seen this with static shocks to switches as well as power spikes and brown outs.
  • Network admins often seem to have problems remembering to save the configurations to NVRAM. Anytime the power is cycled the info is lost.
  • Hubs don’t have configurations that can be lost or corrupted. They either work or they are broken. The only problemt that I have ever seen with a hub is the power supply failing, and that same risk exists with a switch.
  • Hubs are incredibly cheap and available at your favorite street side vendor along with a hot dog with all the fixings. You can also find spare power supplies for your hub in your junk drawer in many cases.

Some other steps that you should take with the heartbeat network is configuring the network connection in the operating system to remove the "Client for Microsoft Networks" and the "File and Printer Sharing for Microsoft Networks" on the General tab for the connection properties. You should also go into the "Internet Protocol TCI/IP" properties and in the advanced properties on the DNS tab you should unselect "Register this connection’s addresses in DNS" and on the WINS tab select the radio button for "Disable NetBIOS over TCP/IP" since the private network does not need them.

 

Even after configuring the private heartbeat network, don’t forget to also configure the public network connections so that they are set for "All communications (mixed network)" so that the public network connections can be used to run the heartbeat if the private network fails for some reason.

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