_c2c_overlay.html.md.erb

##<a id="overlay"></a> Configure the Overlay Network

Container-to-Container Networking uses an overlay network to manage communication between app instances.
By default, each Diego cell in the overlay network is allocated a /24 range that supports 254 containers per cell, one container for each of the usable IP addresses, `.1` through `.254`.
For more information about the overlay network, see [Overlay Network](../../concepts/understand-cf-networking.html#overlay-network) in _Container-to-Container Networking_.

###<a id="cells"></a> Configure the Number of Diego Cells

If you want to modify the number of Diego cells supported by the overlay network, follow the steps below:

1. In Ops Manager, select the PAS tile.
1. Select **Networking**.
1. Under **Overlay Subnet**, enter an IP range for the overlay network. By default, Ops Manager uses `10.255.0.0/16`. Modifying the subnet range allocated to the overlay network changes the number of Diego cells supported in your deployment. Use the table below as a reference.

<table>
  <tr>
    <th>Overlay subnet mask</th>
    <th>Number of cells</th>
    <th>Containers per cell </th>
  </tr>
  <tr>
    <td>/20</td>
    <td>15</td>
    <td>254</td>
  </tr>
  <tr>
    <td>/16</td>
    <td>255</td>
    <td>254</td>
  </tr>
  <tr>
    <td>/12</td>
    <td>4,095</td>
    <td>254</td>
  </tr>
</table>
<p class="note warning"><strong>Warning</strong>: The overlay network IP address range must not conflict with any other IP addresses in the network. If a conflict exists, Diego cells cannot reach any endpoint that has a conflicting IP address.</p>