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Veritas NetBackup™ Administrator's Guide, Volume I

Last Published: 2018-09-19

Product(s): NetBackup (8.1.2)

Platform: Linux,UNIX,Windows

PREFERRED_NETWORK option for NetBackup servers

The PREFERRED_NETWORK option is not needed in an environment if NetBackup is configured with appropriate host names. The operating system must resolve to the correct IP addresses and then route the addresses correctly.

When external constraints prevent the environment from being corrected, PREFERRED_NETWORK entries can be useful in the following situations:

To prevent NetBackup from connecting to specific destination addresses.
To cause NetBackup to connect only to specific destination addresses.
To request a subset of local interfaces for source binding when outbound connections are made.

Caution:

When used for source binding, the operating system may not honor the source binding list provided by NetBackup. If the operating system implements the weak host model, asymmetrical network routing may result. If asymmetrical routing occurs, the remote host may reject the inbound connection if it implements the strong host model. Similarly, stateful network devices may also drop asymmetrical connections. To ensure the use of specific outbound interfaces for specific remote hosts or networks, make sure that the OS name resolution and routing configurations are correct; create static host routes if needed. Ensure that all network drivers properly implement the IP and TCP networking protocols.

The local PREFERRED_NETWORK entries do not affect the forwarding profile that the local host returns to a remote host during initial CORBA connection setup; it will contain all the local plumbed interfaces. However, the End Point Selection algorithm within the remote process will utilize its local PREFERRED_NETWORK entries to evaluate the profile when selecting the destination for the subsequent CORBA connection.

Table: PREFERRED_NETWORK information

Usage	Description
Where to use	On NetBackup servers or clients.
How to use	Use the nbgetconfig and the nbsetconfig commands to view, add, or change the option. For information about these commands, see the NetBackup Commands Reference Guide. The option uses the following syntax: PREFERRED_NETWORK = target[/subnet] directive [source[/subnet]] Note: The *source* option is not allowed for the PROHIBITED directive. Multiple PREFERRED_NETWORK entries can be specified. During evaluation, the entries are sorted by length of target subnet. Entries with the largest (more precise) subnet are compared before entries with a shorter (less precise) subnet. If two entries have equal subnet specification, they are compared in the order configured, from the top of the list to the bottom. If a subnet is not specified, the default is /128 when the address is non-zero and /0 when the address is 0. This applies to both target and source addresses. A subnet of /0 cannot be used with a non-zero address because it effectively negates all of the bits in the address, making the target or the source match every address. For example, 0/0. The following topics describe details about each option: See target[/subnet]. See directive. See source[/subnet].
Equivalent Administration Console property	NetBackup Management > Host Properties > Master Servers > Double-click on server > Preferred Network. See Preferred Network properties.

Usage

Description

Where to use

On NetBackup servers or clients.

How to use

Use the nbgetconfig and the nbsetconfig commands to view, add, or change the option.

For information about these commands, see the NetBackup Commands Reference Guide.

The option uses the following syntax:

PREFERRED_NETWORK = target[/subnet] directive [source[/subnet]]

Note:

The source option is not allowed for the PROHIBITED directive.

Multiple PREFERRED_NETWORK entries can be specified. During evaluation, the entries are sorted by length of target subnet. Entries with the largest (more precise) subnet are compared before entries with a shorter (less precise) subnet. If two entries have equal subnet specification, they are compared in the order configured, from the top of the list to the bottom.

If a subnet is not specified, the default is /128 when the address is non-zero and /0 when the address is 0. This applies to both target and source addresses.

A subnet of /0 cannot be used with a non-zero address because it effectively negates all of the bits in the address, making the target or the source match every address. For example, 0/0.

The following topics describe details about each option:

Equivalent Administration Console property

NetBackup Management > Host Properties > Master Servers > Double-click on server > Preferred Network.

See Preferred Network properties.

See PREFERRED_NETWORK examples.