Logical Interface

A single physical interface can be virtually split into multiple logical interfaces. Logical interfaces can be used to exchange data.

Table 1 Logical interface list

Interface Name

Usage Scenario and Interface Description

DCN serial interface

After DCN is enabled globally, a DCN serial interface is automatically created.

Virtual Ethernet (VE) interface

When an L2VPN accesses multiple L3VPNs, VE interfaces are used to terminate the L2VPN for L3VPN access. Because a common VE interface is bound to only one board, services will be interrupted if the board fails.

Global VE interface

When an L2VPN accesses multiple L3VPNs, global VE interfaces are used to terminate the L2VPN for L3VPN access.

  • A common VE interface is bound to only one board. If the board fails, services on the common VE interface will be interrupted. Unlike common VE interfaces, global VE interfaces support global L2VE and L3VE. Services on global VE interfaces will not be interrupted if some boards fail.

  • The loopback function on global VE interfaces works properly even when a board is powered off or damaged. The loopback process has been optimized on global VE interfaces to enhance the interface forwarding performance.

Global VE interfaces can be created on a device if the device is powered on.

Flexible Ethernet (FlexE) interface

A physical interface in standard Ethernet mode has fixed bandwidth. However, FlexE technology enables one or more physical interfaces to work in FlexE mode and adds them to a group. The total bandwidth of this group can be allocated on demand to logical interfaces in the group. The group to which physical interfaces are added is referred to as a FlexE group. The logical interfaces that share bandwidth of the physical interfaces in the FlexE group are called FlexE interfaces (also referred to as FlexE service interfaces).

FlexE interface bandwidth varies, which allows services to be isolated. Compared with traditional technologies, FlexE technology permits bit-level interface bundling, which solves uneven per-flow or per-packet hashing that challenges traditional trunk technology. In addition, each FlexE interface has a specific MAC address, and forwarding resources between interfaces are isolated. This prevents head-of-line blocking (HOL blocking) that occurs when traditional logical interfaces such as VLAN sub-interfaces are used for forwarding.

FlexE interface technology especially fits scenarios in which high-performance interfaces are required for transport, such as mobile bearer, home broadband, and leased line access. Services of different types are carried on specific FlexE interfaces, and are assigned specific bandwidth. FlexE technology achieves service-specific bandwidth control, and meets network slicing requirements in 5G scenarios.

VLAN channelized sub-interface

A channelized interface can strictly isolate interface bandwidth. A VLAN channelized sub-interface is a channelization-enabled sub-interface of an Ethernet physical interface. Different types of services are carried on different channelized sub-interfaces. Specific bandwidth values are configured on channelized sub-interfaces to strictly isolate bandwidth among different channelized sub-interfaces on the same physical interface. This allows each service to be assigned specific bandwidth and prevents bandwidth preemption among different sub-interfaces.

Loopback interface

A loopback interface can be either of the following:

  • Loopback interface

    If you need the IP address of an interface whose state is always up, you can select the IP address of a loopback interface. A loopback interface has the following advantages:

    • Once a loopback interface is created, its physical status and data link protocol status always stay up, regardless of whether an IP address is configured for the loopback interface.

    • The IP address of a loopback interface can be advertised immediately after being configured. A loopback interface can be assigned an IP address with a 32-bit mask, which reduces address consumption.

    • No link layer protocol can be configured for a loopback interface. Therefore, no data link layer negotiation is required, allowing the link layer protocol status of the interface to stay up.

    • The device drops the packet with a non-local IP address as its destination IP address and a local loopback interface as its outbound interface.

    The advantages of a loopback interface help improve configuration reliability. The IP address of a loopback interface can be used as follows:
    • As the source address of a packet to improve network reliability.
    • Can be used to control an access interface and filter logs to simplify information displaying.

    When a loopback interface monitors an interface monitoring group, the loopback interface may go down. In other cases, the physical status and link protocol status of the loopback interface are up.

  • InLoopback0 interface

    An InLoopBack0 interface is a fixed loopback interface that is automatically created at the system startup.

    An InLoopBack0 interface uses the fixed loopback address to receive data packets destined for the host where the InLoopBack0 interface resides. The loopback address of an InLoopBack0 interface is not advertised.

Null0 interface

A Null0 interface, similar to a null device supported in some operating systems, is automatically created by the system. All data packets sent to a Null0 interface are discarded.

Therefore, you only need to ensure that the data packets to be filtered out are forwarded to a Null0 interface without the need of configuring any ACL.

A Null0 interface is used as follows:
  • Routing loop prevention

    A Null0 interface can be used to prevent routing loops. For example, a route to a Null0 interface is created when a set of routes are summarized.

  • Traffic filtering

    A Null0 interface can filter packets without an ACL.

No IP address or data link layer protocol can be configured on a Null0 interface.

Ethernet sub-interface

An Ethernet sub-interface can be configured on a physical interface or logical interface. It has Layer 3 features and can be configured with an IP address to implement inter-VLAN communication. An Ethernet sub-interface shares the physical layer parameters of the main interface but has independent link layer and network layer parameters. Enabling or disabling an Ethernet sub-interface does not affect the main interface where the sub-interface resides, whereas a change in the main interface status affects the Ethernet sub-interface. Specifically, the Ethernet sub-interface can work properly only if the main interface is up.

Eth-Trunk interface

An Eth-Trunk interface can have multiple physical interfaces bundled to increase bandwidth, improve reliability, and implement load balancing.

For more information, see Trunk.

VLANIF interface

A VLANIF interface belongs to a Layer 3 interface and can be configured with an IP address. A VLANIF interface that has an IP address configured enables a Layer 2 device to communicate with a Layer 3 device. Layer 3 switching combines routing and switching and improves overall network whole performance. After a Layer 3 switch transmits a data flow using a routing table, it generates a mapping between a MAC address and IP address. When the Layer 3 switch receives the same data flow, it transmits the data flow over Layer 2 instead of Layer 3. The routing table must have correct routing entries, so that the Layer 3 switch can transmit the data flow for the first time. A VLANIF interface and a routing protocol must be configured on a Layer 3 switch to ensure Layer 3 route reachability.

Tunnel interface

A tunnel interface is used by an MPLS TE tunnel to forward traffic.

For more information, see Tunnel Interface.

Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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