Sun Cluster 3.1 Data Services Developer's Guide

Multihomed Hosts

The term multihomed host describes a host that is on more than one public network. Such a host has multiple host names and IP addresses. It has one host name-IP address pair for each network. Sun Cluster is designed to permit a host to appear on any number of networks, including just one (the non-multihomed case). Just as the physical host name has multiple host name-IP address pairs, each resource group can have multiple host name-IP address pairs, one for each public network. When Sun Cluster moves a resource group from one physical host to another, the complete set of host name-IP address pairs for that resource group is moved.

The set of host name-IP address pairs for a resource group is configured as logical host name resources contained in the resource group. These network address resources are specified by the system administrator when the resource group is created and configured. The Sun Cluster Data Service API contains facilities for querying these host name-IP address pairs.

Most off-the-shelf data service daemons that have been written for the Solaris environment already handle multihomed hosts properly. Many data services do all their network communication by binding to the Solaris wildcard address INADDR_ANY. This binding automatically causes the data services to handle all the IP addresses for all the network interfaces. INADDR_ANY effectively binds to all IP addresses currently configured on the machine. A data service daemon that uses INADDR_ANY generally does not have to be changed to handle the Sun Cluster logical network addresses.