Apple Mac OS X Server (Administrator’s Guide) - Manual (Page 568)

m If status messages are interrupted on only one network, the secondary server sends email
notification of a network anomaly, but does not acquire the primary server’s IP address.
Email notification is sent when the secondary server detects a failover condition, a network
anomaly, and when the IP address is relinquished back to the primary server.
Normal operation and failover operation are illustrated in the following two diagrams.
Crossover Cable
en1 en1
en0 en0
100.0.0.11 100.0.0.10
10.0.0.1 10.0.0.2
Primary server
(Web server) Secondary server
(mirrors primary
content, but not
running Web
server software)
Normal Operation
Network
Hub
Failover Operation
en0
en1 en1
en0
100.0.0.10 and 100.0.0.11) 100.0.0.10
10.0.0.1 10.0.0.2
Primary server
(Web server) Secondary server
(acquires primary
IP address and
starts Web
server software)
Network
Hub