Use of host IDs offers the following advantages:

• A host ID represents information that is a unique ID within the system. So, even if a multi-domain system contains hosts with identical host names, the host IDs can be used to identify them as separate hosts.
• When a client is moved in a network environment that uses a node identification key, its host name and IP address are changed. This means that the client is no longer recognized as the same client. In contrast, if host IDs are used, the existing asset information for the client is inherited at the client's new location.

A host ID is generated for a client when the client is installed, and is stored in a host ID management file. If a client already has a host ID management file when the client is re-installed, a new host ID is not generated.

A generated host ID is registered in the higher systems. To enable registration, in the Software Distribution Manager Setup dialog box, choose the ID Key for Operations page, and then select Yes for Use host IDs.

The host ID is registered automatically in higher systems as shown in the following figure.

Figure 6-1 Automatic registration of host IDs

The following table shows the times at which host IDs are registered automatically in the next-higher system, depending on the settings for automatic registration of system configuration information.

Table 6-1 Times at which host IDs are registered automatically in the next-higher system

Is system configuration information registered automatically?	Automatic registration times
Yes	When the client is installed. Whenever the connection server is changed during setup Whenever the host name, IP address, or host ID is changed Whenever the setup contents are registered Whenever a connection is made to a higher system (if the host ID has not been registered in that higher system)
No	When connection is established with a higher system (if the host ID has not been registered in that higher system, or after the host ID has been changed)

In a system in which multiple managing servers are configured in a hierarchy, if you wish to upgrade a JP1/Software Distribution Manager that does not support host IDs and then use host IDs, after you upgrade the higher JP1/Software Distribution Manager you must then upgrade the lower JP1/Software Distribution Managers.