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Veritas NetBackup™ Administrator's Guide, Volume I

Last Published: 2017-09-25

Product(s): NetBackup (8.1)

PREFERRED_NETWORK option for NetBackup servers

The PREFERRED_NETWORK option replaces the REQUIRED_INTERFACE and REQUIRED_NETWORK entries.

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.

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]
	The *target[/subnet]* is a host name or range of addresses to be compared to the prospective source or destination addresses being evaluated. The following are examples of how to indicate a target or a subnet: A host name: myserver.domain An IP address: 10.82.105.11 A network with subnet: 10.82.105.0/21 Any IPv4 address: 0.0.0.0 Any IPv6 address: 0::0 Any address: 0/0 Note: A host or a network name that cannot resolve causes the *target* to be ignored. However, any associated *source* is added to the source binding list.
	The *directive* (MATCH, ONLY, or PROHIBITED) determines how the *target* is compared to the source or the destination address that is under evaluation. MATCH This directive applies to destination addresses. If the address being evaluated matches the *target, then the address is immediately selected to be used and evaluation stops. If a target* is not matched, evaluation continues with the next entry. ONLY This directive applies to destination addresses. If the address under evaluation does not match a *target, it is not used and evaluation stops for this address. If the destination is the only potential destination, the connection is not attempted. If there is an additional potential destination, it is evaluated starting over with the first entry. PROHIBITED* The *target* applies to both the source and the destination addresses. If a *source* is specified, it is ignored and the *target* is still prohibited. If the matched address is a destination address, evaluation stops. If the matched address was the only potential destination, no connection is attempted. If there are additional potential destinations, they are evaluated starting over with the first entry. If the matched address is a source address, it is removed from the binding list. If *source* entries exist, the shortened binding list may not be used. On some platforms, prohibiting a local interface may cause unexpected results when NetBackup connects to remote hosts. Prohibiting a local interface does not affect the connections that are internal to the host.
	Indicating a *source[/subnet]* is optional. This is a host name or IP address range that is requested to be used as the local interface for outbound connection to addresses in *target. The source* applies to the directives ONLY and MATCH, but not to the directive PROHIBITED. Notes: The operating system may not honor the *source* request. NetBackup does not request a *source* which has already been PROHIBITED. A host or a network name that cannot be resolved is ignored, but the evaluation status of the *target* is still used.
Equivalent Administration Console property	NetBackup Management > Host Properties > Master Servers > Double-click on server > Preferred Network. See Preferred Network properties.

The following Support document contains more information about using the PREFERRED_NETWORK option:

http://www.veritas.com/docs/HOWTO60779

Examples of the PROHIBITED directive

An example that prevents the host from using IPv4 addresses:
```
PREFERRED_NETWORK = 0.0.0.0 PROHIBITED
```
An example that prevents the host from using IPv6 addresses:
```
PREFERRED_NETWORK = 0::0 PROHIBITED
```
This example prevents the host from using the address of the production_server:
```
PREFERRED_NETWORK = production_server PROHIBITED
```
This example prevents NetBackup from using any address between 12.34.0.0 and 12.34.255.255 as the source or destination for a connection. If it matches a local interface, NetBackup provides an ordered list of the remaining interfaces as the source binding list for the outbound interface when other entries do not specify a source. The operating system may always use the first one in the list instead of using the network routing tables to select the best one.
```
PREFERRED_NETWORK = 12.34.56.78/16 PROHIBITED
```

Examples of the ONLY directive

This example instructs the host to use only IPv6 addresses in that subnet range:
```
PREFERRED_NETWORK = 2001:1234:1efc::/48 ONLY
```
This example prevents NetBackup from connecting to any destination address outside the range of 12.34.56.0 to 12.34.56.255. The entry does not affect outbound interface selection.
```
PREFERRED_NETWORK = 12.34.56.78/24 ONLY
```
This example prevents NetBackup from connecting to any destination address outside the range of 12.34.56.0 to 12.34.56.255. The entry requests that the operating system use 98.76.54.32 as the outbound interface.
```
PREFERRED_NETWORK = 12.34.56.78/24 ONLY 98.76.54.32
```

Examples of the MATCH directive

This example instructs the host to use the interface IPs of Host_A for all IPv4 and IPv6 addresses. The entry can appear multiple times in the configuration file.
```
PREFERRED_NETWORK  = 0/0 MATCH Host_A
```
This example allows connectivity to the host names that resolve to 12.34.0.0 to 12.23.255.255. The entry does not affect outbound interface selection:
```
PREFERRED_NETWORK = 12.34.0.0/16 MATCH
```
This example allows connectivity to the host name that resolves to 12.34.56.78, and requests that the operating system use 98.76.54.32 as the outbound interface:
```
PREFERRED_NETWORK = 12.34.56.78 MATCH 98.76.54.32
```