3Com 10014299 manual Configure Loopback, Null Interface

156CHAPTER 11: CONFIGURING LOGICAL INTERFACE

	Some applications (such as configuring local peer of SNA) requires that a local
	interface with specified IP address should be configured without affecting physical
	interface configuration. Furthermore, this address should have a 32-bit mask to
	reduce the use of IP addresses and it should be advertised by the routing
	protocols. Therefore, the loopback interface is added to meet this requirement.
Configure Loopback	Loopback interface configuration includes:
Interface	■ Create the loopback interface

■ Configure operating parameters of the interfacE

1Create loopback interface

Table 187 Create/delete loopback interface

Operation	Command
Create the loopback interface and enter loopback	interface loopback number
interface view
Delete the specified loopback interface	undo interface loopback
	number

2Configure operating parameters on the interface

The parameters such as IP address and IP routing can be configured on loopback interface. For detailed configuration, refer to Operation Manual – Network Protocol.

The 32-bit mask can be configured for the loopback interface, that is, the mask can be 255.255.255.255. The IP address with this 32-bit mask can be advertised by the routing protocols.

When configuring the ip address of loopback interface, it is recommended to configure the 32bit mask to save the ip address.

Null Interface	The 3Com Router support Null interface. Null interface is always in UP status, but
	cannot forward data packet or configure IP address or encapsulate other
	protocols.
	Null interface is a virtual interface. Any network data packet sent to this interface
	will be dropped.

Configure Null Interface Null interface configuration includes:

■Create the Null interface

■Configure operating parameters of the interface

1Create the Null interface

Only one interface Null 0 can be created on the 3Com Router. Please perform the following configurations in all views.

Table 188 Create/Delete Null interface:

Operation	Command
Create the Null interface and enter Null interface view	interface null 0
Delete the Null interface	undo interface null 0