anchor.diff:  
   <p class="note"><b>Note:</b> Always use an odd number of AZs. This ensures that your deployment remains available when greater than half of the AZs are available. For example, a deployment with three AZs stays available when one AZ goes down and two AZs are still available.</p>
   
  -## <a id='external-lbs'></a> External Load Balancers for High Availability
  +### <a id='external-lbs'></a> External Load Balancers
   
   External load balancers distribute traffic coming from the internet to your internal network. 
   
  
positive.code: For more information about scaling applications and maintaining app uptime, see the following topics:
  
  * [Scaling an Application Using cf scale](../devguide/deploy-apps/cf-scale.html)
  *[Using Blue-Green Deployment to Reduce Downtime and Risk](../devguide/deploy-apps/blue-green.html).
  
  ### <a id='vert-scaling'></a> Scale Vertically
  
  
negative.code: 
  You can horizontally scale most <%= vars.product_short %> component VMs to multiple instances for high availability. 
  
  You should also distribute the instances of components across different AZs to minimize downtime during ongoing operation, product updates, and platform upgrades. For more information about using AZs, see [Availability Zones](#azs).
  
  ## <a id='instance-counts'></a> Recommended Instance Counts for High Availability
  
  <%= vars.scaling_ert %>
  
  <%= partial vars.scale_table %>
  
  
  ## <a id='supporting-scaling'></a> Infrastructure to Support Component Scaling
  
  The ability to scale component VMs is important for high availability. To scale component VMs, you must ensure that the surrounding infrastructure of your deployment supports VM scaling.
  
  This section describes the infrastructure required to support scaling component VMs for high availability.
  
  