4. What is the state of the loopback interface 0 when the command loopback interface 0 is used? CLI Interface Configuration RTA GO/0/0 RTB 10.0.12.1/24 RH1.1.1.1/32 GO/0/0 Configure an IP address of 10.0.12.1/24 on interface G0/0/0 and an IP address of 1.1.1.1/32 on loopback interface 0. system-view [Huawei] interface GigabitEthernet 0/0/0 [Huawei-GigabitEthernet0/0/01 ip address 10.0.12.1 255.255.255.0 [Huawei-GigabitEthernet0/0/0] interface loopback 0 [Huawei-LoopBack0lip address 1.1.1.1 32 In order to run IP services on an interface, an IP address must be configured for the interface. Generally, an interface needs only the primary IP address. In special cases, it is possible for a secondary IP address to be configured for the interface. For example, when an interface of a router such as the AR2200 connects to a physical network, and hosts on this physical network belong to two network segments. In order to allow the AR2200 to communicate with all the hosts on the physical network, configure a primary IP address and a secondary IP address for the interface. The interface has only one primary IP address. If a new primary IP address is configured on an interface that already has a primary IP address, the new IP address overrides the original one. The IP address can be configured for an interface using the command ip address {mask | mask-length} where mask represents the 32 bit subnet mask e.g. 255.255.255.0, and mask-length represents the alternative mask-length value e.g. 24, both of which can be used interchangeably. The loopback interface represents a logical interface that is applied to represent a network or IP host address, and is often used as a form of management interface in support of a number of protocols through which communication is made to the IP address of the loopback interface, as opposed to the IP address of the physical interface on which data is being received.