Apple Mac OS X Server Setting Up IP Failover, IP Failover Prerequisites, IP Failover Operation

Setting Up IP Failover

IP failover allows a secondary server to acquire the IP address of a primary server if the primary server ceases to function. Once the primary server returns to normal operation, the secondary server relinquishes the IP address. This allows your website to remain available on the network even if the primary server temporarily goes offline.

Note: IP failover only allows a secondary server to acquire a primary server’s IP address. You need additional software tools, such as rsync, to provide capabilities such as mirroring the primary server’s data on the secondary server. See the rsync man page for more information.

IP Failover Prerequisites

IP failover isn’t a complete solution; it is one tool you can use to increase your server’s availability to your clients. To use IP failover, you need to set up the following hardware and software.

Hardware Requirements

IP failover requires the following hardware setup:

ÂPrimary server

ÂSecondary server

ÂPublic network (the servers must be on same subnet)

ÂPrivate network between the servers (requires an additional network interface card)

Note: Because IP failover uses broadcast messages, both servers must have IP addresses on the same subnet of the public network. Both servers must also have IP addresses on the same subnet of the private network.

Software Requirements

IP failover requires the following software setup:

ÂUnique IP addresses for each network interface (public and private)

ÂSoftware to mirror primary server data to the secondary server

ÂScripts to control failover behavior on the secondary server

IP Failover Operation

When IP failover is active, the primary server periodically broadcasts a brief message confirming normal operation on both the public and private networks. This message is monitored by the secondary server.

ÂIf the broadcast is interrupted on both public and private networks, the secondary server initiates the failover process.

ÂIf status messages are interrupted on only one network, the secondary server sends email notification of a network anomaly, but doesn’t acquire the primary server’s IP address.

Chapter 14 Working with Network Services

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