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How to Add a New Subnet to an Existing VM Network on VSphere

Environment

 Product  Version
 Pivotal Cloud Foundry® (PCF)

 1.7, 1.8, 1.9 

Symptom

In VSphere, when attempting to add a new subnet to an existing VM Network, you will inevitably have to select an availability zone in which to place the subnet. One might do this in order to add a new pool of IP addresses to the PCF environment to avoid running out. When selecting the Availability Zone to place the subnet in, and there's only one to choose from, you may see the following error:

A network's subnets must not have overlapping Availability Zones

Cause

This is currently a limitation with Ops Manager as it handles most of the networking/IP address Management, but this is not a limitation in BOSH. At this time, there aren't any plans to change this, however, to get around this problem, follow the resolution steps below.

Resolution

1.) Log into vSphere.

2.) Create a new resource pool.

3.) In Ops Manager, create a new Availability Zone using the resource pool created from step #2. This will be used by the subnet you're going to add.

4.) After this, if you attempt to balance new jobs in the new Availability Zone, you'll notice you're unable to. This is due to a protection feature of Ops Manager.

5.) To get around this, you'll need to enable Advanced Mode in Ops Manager. After doing so, you should be able to select to use the new Availability Zone.

Note: This was observed in a VSphere PCF 1.7 Environment.

Impact/Risk

Using Ops Manager while it is in advanced mode disables some of the protections that Ops Manager provides for you. This will allow you to make changes that could potentially be dangerous to your installation of Pivotal Cloud Foundry® (PCF). Pivotal does not recommend enabling advanced mode unless you have been directed to do so by Pivotal Support. Even then, please proceed with caution when advanced mode is enabled and disable advanced mode once you have completed the change that you set out to make.

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