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ME60 V800R010C10SPC500 Configuration Guide - LAN Access and MAN Access 01

This is ME60 V800R010C10SPC500 Configuration Guide - LAN Access and MAN Access
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Overview of Ethernet Interfaces

Overview of Ethernet Interfaces

Ethernet interfaces include conventional Ethernet interfaces, Fast Ethernet (FE) interfaces, and Gigabit Ethernet (GE) interfaces.


Both Ethernet and token ring networks are typical types of LANs. The Ethernet technology has become the most important LAN networking technology because it is flexible, simple, and easy to implement.

The ME60 supports the following types of Ethernet interfaces:

  • GE interfaces: comply with 1000Base-TX physical layer specifications and are compatible with the 10Base-T and 100Base-TX physical layer specifications.

  • 10GE interfaces comply: with IEEE 802.3ae and are compatible with 10Base-T, 100Base-TX, and 1000Base-TX physical layer specifications.

Ethernet electrical interfaces can work in either full-duplex or half-duplex mode. They support auto-negotiation. In auto-negotiation mode, they negotiate with other network devices for the most suitable duplex mode and rate. This simplifies system configuration and management.

Basic Concepts of Ethernet Interfaces

  • Ethernet interface type

    Table 3-1 shows the types of Ethernet interfaces defined on the device. Ethernet interfaces are classified into different types to meet various network requirements.

    Table 3-1 Ethernet interface type

    Interface type


    Layer 3 Ethernet interface

    A physical interface that operates at the network layer. The interface can be configured with an IP address, supporting Layer 3 protocols and providing routing functions.

    Layer 3 Ethernet sub-interface

    A logical interface that is configured on a main interface. The main interface can be a physical interface (such as a Layer 3 Ethernet interface) or a logical interface. The Layer 3 Ethernet sub-interface shares physical layer parameters of the main interface and can be configured with specific link layer and network layer parameters. You can activate or deactivate the sub-interface, without affecting the performance of the main interface. The change of the main interface status, however, affects the sub-interface. The sub-interface functions properly only if the main interface is in the Up state.

  • Ethernet interface rate and duplex mode


    The Ethernet interface rate and duplex mode are described as follows: Ethernet optical interfaces support the auto-negotiation mode but not the setting of interface rates and duplex modes.

    By default, the Ethernet interface rate and duplex mode are automatically negotiated. Auto-negotiation means that the local device automatically adjusts the interface rate and duplex mode based on the interface rate and duplex mode of the peer so that both ends can work in the same duplex mode at the highest possible speed.

    It is recommended to configure auto-negotiation in compliance with the automatic negotiation standard for Ethernet interfaces. If two ends of a link work at unmatched interface rates or in unmatched duplex modes, you need to disable auto-negotiation and manually set the interface rates and duplex modes.

    Manually setting interface rate and duplex mode usually complicates network planning and maintenance, and incorrect settings may affect or even interrupt the communication on a network.

    • If the rate of one end of a link is set to 10 Mbit/s and the rate of the other end to 100 Mbit/s, the link goes Down.

    • If one end of a link works in a duplex mode at a fixed rate (such as 10 Mbit/s or 100 Mbit/s) while the other end works in auto-negotiation mode, the interface working in auto-negotiation mode can detect the fixed rate of the peer interface but cannot detect that the peer device works in the duplex mode. In this case, even if negotiation between the two ends succeeds, the interface working in auto-negotiation mode adopts the default working mode, 10M half duplex.

      That is, if one end works in auto-negotiation mode while the other end works in a fixed mode, the auto-negotiation mechanism does not take effect. To implement the auto-negotiation mechanism, both the communicating parties must work in auto-negotiation mode.

    • If one end of a link works in full-duplex mode while the other end works in half-duplex mode, communication performance of the interfaces is affected.

    Manually setting the interface rate and duplex mode is recommended only when auto-negotiation of an Ethernet link fails. When there is an auto-negotiation problem, upgrade software or hardware to support the auto-negotiation mechanism defined in IEEE 802.3u/z.


    The poor quality of network cables may also cause auto-negotiation failures.

  • Maximum transmission unit (MTU)

    MTU is the largest packet of data that can be transmitted on a network, expressed in bytes. MTU is determined by data link layer protocols, and MTU values vary with networks.

    The size of packets is limited at the network layer. Whenever receiving an IP packet, the IP layer determines the next-hop interface for the packet and obtains the MTU configured on the interface. Then, the IP layer compares the MTU with the packet length. If the packet length is longer than the MTU, the IP layer fragments the packet into smaller packets, which are shorter than or equal to the MTU. If unfragmentation is configured, some packets may be discarded during data transmission at the IP layer.

    If the size of packets is much greater than the configured MTU value, the packets are broken into a great number of fragments. The packets may be discarded by quality of service (QoS) queues.

  • LAN/WAN mode of 10GE interfaces

    A ten-GigabitEthernet (10GE) interface can operate in either of the following modes in terms of its physical feature:
    • LAN mode: In this mode, the 10GE interface transmits Ethernet packets and connects to an Ethernet network.
    • WAN mode: In this mode, the 10GE interface transmits Synchronous Digital Hierarchy (SDH) frames and connects to an SDH network.

      The 10GE interface in WAN mode supports only point-to-point (P2P) packet transmission.


      A 10GE interface in WAN mode encapsulates Ethernet packets to SDH frames.

  • Overhead bytes

    SDH frames contain various overhead bytes that are used to implement operation and maintenance functions, such as layered management of SDH transport networks. J0 and J1 are used for interoperability between devices of different countries, areas, or manufacturers.

  • Loopback test functions of Ethernet interfaces

    By enabling the loopback test functions on an Ethernet interface, you can check whether the Ethernet interface operates properly.

    The loopback test functions of Ethernet interfaces include:

    • Internal loopback test: establishes a loop within the switching chip to check whether certain hardware of the Ethernet interface is faulty.

    • External loopback test: After receiving packets from a peer end, the local end sends the packets back to the peer end but does not forward the packets to their destination addresses. The external loopback test is used to detect whether a link between the local and peer ends is faulty.

    • An Ethernet interface cannot properly forward packets during the loopback test.

    • When an Ethernet interface is in the Down state, you can only perform the internal loopback test.

      After running the shutdown command in the view of a specified Ethernet interface and the interface status is displayed as Administratively Down, you cannot perform either the internal loopback test or the external loopback test on the Ethernet interface.

    • The shutdown command cannot be run on an Ethernet interface during the loopback test.

    • After the loopback test function is enabled on an Ethernet interface, the interface operates in full-duplex mode. After the loopback test function is disabled, the Ethernet interface restores the original settings.

Updated: 2019-01-04

Document ID: EDOC1100059440

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