User's Manual

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22.5 Configuring Logical Interface
This section describes how to configure a logical interface. The contents are as follows:
 Configuring null interface
 Configuring loopback interface.
 Configuring aggregation interface
 Configuring VLAN interface
 Configuring SuperVLAN interface
22.5.1 Configuring Null Interface
The whole system supports only one null interface. Its functions are similar to those of applied null devices on
most operating systems. The null interface is always available, but it never sends or receives communication
information. The null interface provides an optional method to filtrate communication. That is, the unwanted
network communication can be routed to the null interface; the null interface can function as the access control
list.
You can run the following command in global configuration mode to specify the null interface:
Command Usage Guidelines
interface null
0 Enters the null interface configuration state.
The null interface can be applied in any command that takes the interface type as its parameter.
The following example shows how to configure a null interface for the routing of IP 192.168.20.0.
ip route 192.168.20.0 255.255.255.0 null 0
22.5.2 Configuring Loopback Interface
The loopback interface is a logical interface. It always functions and continues BGP session even in the case
that the outward interface is shut down. The loopback interface can be used as the terminal address for BGP
session. If other switches try to reach the loopback interface, a dynamic routing protocol should be configured
to broadcast the routes with loopback interface address. Messages that are routed to the loopback interface
can be re-routed to the switch and be handled locally. For messages that are routed to the loopback interface
but whose destination is not the IP address of the loopback interface, they will be dropped. This means that
the loopback interface functions as the null interface.
Run the following command in global configuration mode to specify a loopback interface and enter the interface
configuration state:
Command Usage Guidelines
interface loopback
number Enter the loopback interface configuration state.
22.5.3 Configuring Aggregation Interface
The aggregator interface is introduced in the background that the bandwidth of a single Ethernet interface is
insufficient. It can bind together multiple full-duplex interfaces of the same rate to multiply the bandwidth.
Run the following command to define the aggregation interface: