Specifications

248 Chapter 14 Configuring and Managing Network Services
Hardware Requirements
IP failover requires the following hardware setup:
 Primary server
 Secondary server
 Public network (the servers must be on same subnet)
 Private network between 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:
 Unique IP addresses for each network interface (public and private)
 Software to mirror primary server data to the secondary server
 Scripts 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 the public and private networks. This message is
monitored by the secondary server.
 If the broadcast is interrupted on both public and private networks, the secondary
server initiates the failover process.
 If status messages are interrupted on only one network, the secondary server sends a
mail notification of a network anomaly, but doesn’t acquire the primary server’s IP
address.
Mail notification is sent when the secondary server detects a failover condition or a
network anomaly and when the IP address is relinquished back to the primary server.
Enabling IP Failover
You enable IP failover by adding command lines to the file /etc/hostconfig on the
primary and the secondary server. Enter these lines exactly as shown, with regard to
spaces and punctuation marks.
To enable IP failover:
1 On the primary server, add the following line to /etc/hostconfig:
FAILOVER_BCAST_IPS="10.0.0.255 100.0.255.255"
Substitute the broadcast addresses used on your server for the public and private
networks. This instructs the server to send broadcast messages over relevant network
interfaces, indicating that the server at those IP addresses is functioning.
2 Restart the primary server so your changes can take effect.