Virtual interfaces on a NetCache appliance

About virtual interfaces

The feature that supports trunking on the NetCache appliance is known as a virtual interface. After being created, a virtual interface is indistinguishable from a physical network interface.

Types of virtual interfaces

There are two types of virtual interfaces:

Single-mode
Multi-mode

Single-mode virtual interface operation

In a single-mode virtual interface, all interfaces that constitute the virtual interface share an IP address and a media access control (MAC) address. However, only one interface in the virtual interface is active. The other interfaces are on standby, ready to take over if the active interface fails. Failure means that the link status of the interface is down, which signals that the interface has lost connection with the switch.

Note
When you create a single-mode virtual interface, an interface is selected randomly to be the active interface. However, if you want to specify a certain interface to be active, you can override the random selection and specify that interface as preferred. For example, if you want to make a standby or a new interface active, you must make that interface the preferred interface. There can only be one preferred interface in a single-mode virtual interface.

A single-mode virtual interface can recover from a failure of up to (n-1) interfaces, where n is the total number of interfaces that form the virtual interface.

Example

In the following illustration, e0 and e1 are part of the SingleVIF1 single-mode virtual interface. The active interface, e0, fails. The e1 interface takes over and maintains the connection to the switch.

Multi-mode virtual interface operation

In a multi-mode virtual interface, all the interfaces in the virtual interface are active at the same time. This logical aggregation of links provides higher throughput than possible if the interfaces were configured as a single-mode virtual interface.

With a multi-mode virtual interface, NetCache load balances outgoing traffic over the outgoing interfaces that are trunked. The switch automatically balances the load among the interfaces of the virtual interface if the following conditions are met:

The switch supports trunking over multiple ports
The switch is configured so that all ports to which links of a virtual interface are connected are part of a single logical port and share a common MAC address.

For information about configuring the switch, see your switch vendor's documentation.

Note
Some switches might not support trunking of ports configured for jumbo frames. For more information, see your switch vendor's documentation.

A multi-mode virtual interface can recover from a failure of up to (n-1) interfaces, where n is the total number of interfaces that form the virtual interface.

Example

In the following illustration, e0, e1, e2, and e3 are part of the MultiVIF1 multi-mode virtual interface. All four interfaces in the MultiVIF1 multi-mode virtual interface are active.

In the preceding illustration, if any three of the interfaces were to fail one-by-one or simultaneously, the NetCache appliance still stays connected to the network.

Routing on a NetCache appliance with a multi-mode virtual interface

If this physical interface goes down or is removed from the multi-mode virtual interface, load balancing occurs over the remaining interfaces.

Prerequisites to creating a virtual interface

Before creating a virtual interface, you need to

Identify the interfaces you want to aggregate into the virtual interface on your NetCache appliance.
If you are creating a multi-mode virtual interface, configure a switch that supports trunking over multiple port connections according to your switch vendor's instructions.