How the appliance determines outbound interfaces to use

Default behavior for determining outbound interface use

By default, NetCache binds all types of traffic to all interfaces. You can, however, bind specific types of traffic to specific interfaces to balance the load across interfaces or to provide an additional level of security. Any time you bind traffic to a particular interface, NetCache sends or accepts that type of traffic only on that interface.

By default, if the NetCache appliance has multiple interfaces, NetCache performs a route lookup when it receives a request and selects the interface closest to the origin server. NetCache performs only one route lookup, and it selects the most efficient route to the server. Therefore, in typical circumstances, you do not need to configure NetCache to instruct NetCache how to select the outbound interfaces.

Options for controlling outbound interface use

In some circumstances, however, it is desirable to control the interfaces that NetCache selects for traffic to servers. The following two options are available to influence how NetCache selects the interfaces to use for outgoing traffic:

Load Balancing Interfaces option
Organizations that need to balance responses from servers across multiple lines can use this option. By specifying the interfaces over which NetCache is to balance outgoing traffic, responses from origin servers are distributed over multiple lines on their way to the NetCache appliance. See About balancing server-to-NetCache traffic over interfaces for more information.
Disabled Outgoing Interfaces option
This option enables you to identify outgoing interfaces that you do not want NetCache to use. See About restricting interfaces for connecting to servers for more information.

The following table shows how these two option settings control outbound interface selection.

Load Balancing Interfaces setting	Disabled Outgoing Interfaces setting	What NetCache does
No interfaces are listed.	No interfaces are listed.	NetCache uses the interface closest to the server.
No interfaces are listed.	An interface is listed, for example, E0.	NetCache includes all interfaces in its load balancing determination except for interfaces listed in the Disabled Outgoing Interfaces option. Note For the first packet and for UDP, NetCache performs a route lookup.
Specific interfaces are listed, for example, E7 and E8.	No interfaces are listed.	NetCache balances traffic only over the interfaces listed in the Load Balancing Interfaces option (in this example, only over E7 and E8 and any aliases of E7 and E8). Note For the first packet and for UDP, NetCache performs a route lookup and might select an interface not listed in the Load balancing Interfaces option.

Load Balancing Interfaces setting

Disabled Outgoing Interfaces setting

What NetCache does

No interfaces are listed.

NetCache uses the interface closest to the server.

No interfaces are listed.

An interface is listed, for example, E0.

NetCache includes all interfaces in its load balancing determination except for interfaces listed in the Disabled Outgoing Interfaces option.

Note
For the first packet and for UDP, NetCache performs a route lookup.

Specific interfaces are listed, for example, E7 and E8.

No interfaces are listed.

NetCache balances traffic only over the interfaces listed in the Load Balancing Interfaces option (in this example, only over E7 and E8 and any aliases of E7 and E8).

Note
For the first packet and for UDP, NetCache performs a route lookup and might select an interface not listed in the Load balancing Interfaces option.