About the Access IP Addresses

OpenStack deployments generally provide new servers 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?

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