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Duplicate cluster ID numbers

Created: 08 Nov 2012 • Updated: 08 Nov 2012 | 2 comments
This issue has been solved. See solution.

Hello All,

VCS version (4.0 to 5.1)

OS version AIX, Solaris, Linux

    I have a question about Cluster ID numbers and the need for them to be unique. For the most part we have just assigned cluster ID numbers on pretty much of an add-hoc basis, with no one keeping track fo the ID #'s. This has worked for since many of our clusters use crossover cables or private vlans that were unique to each cluster.

     However, we are now starting to use blade servers in HP enclosures where the pVlan is shared between multiple clusters. We have found a problem where LLT will not start when the smae ID number is used on multiple clusters.

Now it does say Unique Cluster ID number during the VCS install/configuration. However, we have gotten away with using duplicate ID's in the past.

What I was hoping for want an explanation of how LLT works WRT to cluster ID's and pVlans.

So can anyone help me out here?

Thanks in Advance,


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mikebounds's picture

It sounds as though you have answered your own question, so I am not quite sure what you are asking.

Let me draw an anology.  IP addresses should to be unique, but if you have 2 nodes with the same IP, if the 2 servers are isloated from each other on the network, it won't cause an issue, but if you then put these 2 servers on the same network, then you will have a clash of IP.

The ClusterID is used in conjunction with the Node id (defined in llthosts) to uniquely identify each node in a cluster and so you can't use the same cluster id for clusters using heartbeats on the same VLAN, but if the heartbeats of 2 different clusters are not connected at a network level, then duplicate cluster ids are not going to cause an issue.

You may find download helpful in determining what cluster ids you are using so that when you move a cluster to the shared heartbeat VLAN you can check what cluster ids you can't use


UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows

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GeorgeC's picture


    What I was asking for was how deos LLT work. You duplicate IP issustration answered it perfectly. Thank you the confirmation. I guess I had an idea of what was going on with LLT and cluster ID's but, really needed a sanity check...

Thanks again,