About the Access IP Addresses
  =============================
  
  OpenStack deployments generally provide new [servers](servers.md) with one
  or two network interfaces, each with its own address(es). Usually, one of
  these will be a public interface, with its addresses available on the Internet.
  
  However, in some cases, the servers are created on an internal network
  (this is especially common in a hybrid solution where physical and virtual
  servers are intermixed). The servers may be behind a NAT device, firewall,
  or other network device that prohibits direct access to the server itself.
  
  The `Server` object provides two attributes that are used to instruct
  applications what IP address to use. These are called the *access IP*
  addresses, and they are, in essence, documentation strings used to
  direct applications to the correct network address. They can be changed
  at will by the server's owner, and OpenStack Nova does not perform any
  validation on them:
  
  * `accessIPv4` holds the IPv4 access address, and
  * `accessIPv6` holds the IPv6 access address.
  
  ### Updating the access IP address(es)
  
  For example, you may have a private cloud with internal addresses in the
  10.1.x range. However, you can access a server via a firewall device at
  address 50.57.94.244. In this case, you can change the `accessIPv4` attribute
  to point to the firewall:
  
      $compute = $cloud->Compute();
      $server = $compute->Server('908c5617-26c2-4535-99a9-3f20e4b74835');
      $server->Update(array('accessIPv4'=>'50.57.94.244'));
  
  When a client application retrieves the server's information, it will know
  that it needs to use the `accessIPv4` address to connect to the server, and
  *not* the IP address assigned to one of the network interfaces.
  
  ### Retrieving the server's IP address
  
  The `Server::ip()` method is used to retrieve the server's IP address.
  It has one optional parameter: the format (either IPv4 or IPv6) of the address
  to return (by default, it returns the IPv4 address):
  
  	$server = $compute->Server('...');	// get a server
  	print $server->ip();				// the IPv4 address
  	print $server->ip(4);				// the IPv4 address, too
  	print $server->ip(6);				// the IPv6 address
  	print $server->ip(8);				// causes an exception
  
  ## What next?
  
  Return to the [Table of Contents](toc.md)