I'm quite interested in finding out the general consencus on the best-practice for using a prefix for inter-cluster calls and why. I have generally been of the view that the prefix used for inter-cluster calls should use the IDD code of the country, but a colleague is suggesting an arbitrary prefix for each cluster.
As an example, consider this. There is Cluster1 in Australia and Cluster2 in China.
Cluster1 has an office that uses 6000-6999 for extensions and Cluster2 has an office that uses 6000-6499 for extensions. I have proposed using IDD codes, so Cluster1 calling Cluster2 would become 866000 and Cluster2 calling Cluster1 would become 616000. The colleague has suggested for Cluster1 calling Cluster2 to use a prefix of 06 (thus becoming 066000) and Cluster2 calling Cluster1 to use a prefix of 01 (thus becoming 016000).
My main concern is that a prefix of "0" is used for external calls on Cluster1, but otherwise I think both ideas would work.
Am I missing anything?