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    2-4-1 RLDP

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    Daniel Ibarra O
    RLDP is a protocol developed by Ruijie to rapidly detect Ethernet link failures through the use of probe and echo packets. It can detect one-way link failures, two-way link failures, and loops on switch ports. If a failure is detected, RLDP will process it according to the user configuration, such as generating alarms, shutting down ports, or disabling port learning. RLDP is useful for access layer switches to detect self-loops or downstream hub loops that cannot be prevented by STP.

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    2-4-1 RLDP

    Uploaded by

    Daniel Ibarra O
    113 views10 pages
    RLDP is a protocol developed by Ruijie to rapidly detect Ethernet link failures through the use of probe and echo packets. It can detect one-way link failures, two-way link failures, and loops on switch ports. If a failure is detected, RLDP will process it according to the user configuration, such as generating alarms, shutting down ports, or disabling port learning. RLDP is useful for access layer switches to detect self-loops or downstream hub loops that cannot be prevented by STP.

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    RLDP is a protocol developed by Ruijie to rapidly detect Ethernet link failures through the use of probe and echo packets. It can detect one-way link failures, two-way link failures, and loops on switch ports. If a failure is detected, RLDP will process it according to the user configuration, such as generating alarms, shutting down ports, or disabling port learning. RLDP is useful for access layer switches to detect self-loops or downstream hub loops that cannot be prevented by STP.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    113 views10 pages

    2-4-1 RLDP

    Uploaded by

    Daniel Ibarra O
    RLDP is a protocol developed by Ruijie to rapidly detect Ethernet link failures through the use of probe and echo packets. It can detect one-way link failures, two-way link failures, and loops on switch ports. If a failure is detected, RLDP will process it according to the user configuration, such as generating alarms, shutting down ports, or disabling port learning. RLDP is useful for access layer switches to detect self-loops or downstream hub loops that cannot be prevented by STP.

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    of 10

    RLDP Principle

    RLDP Overview

    Rapid Link Detection Protocol (RLDP) is developed by Ruijie for rapidly detecting Ethernet link
    failures.

    General Ethernet link detection mechanisms detect link connectivity based on physical connection
    status and automatic negotiation at the physical layer. Such mechanisms have limitations and cannot
    provide users with reliable link detection information in specific scenarios.
    o Scenario 1: Among the optical fiber of port SW1, the core receiving signals fails while the core transmitting signals is normal. As a
    fiber converter exists, the peer device displays normal Tx and Rx (the device transmits and receives signals successfully).
    o Scenario 2: An Internet service provider (ISP) transmission network exists between two Ethernet devices. If the network fails, the
    Ethernet devices at both ends cannot sense.

    SW1 SW2

    Rx Rx

    Tx Tx
    RLDP Principle

    RLDP defines two kinds of protocol packets: probe packet and echo packet, whose destination
    address is L2 multicast address (01-d0-f8-00-00-02).

    Each port with RLDP configured and in link up state periodically sends its probe packets and waits for
    adjacent ports to respond to the probe packet. It also expects probe packets from adjacent ports. If a
    link is normal both physically and logically, the port should be able to receive an echo packet and a
    probe packet from the adjacent port. Otherwise, the link is considered abnormal.

    Ruijie RLDP provides three functions: loop detection, one-way link detection, and both-way link
    detection.

    RLDP Probe
    RLDP Echo
    RLDP Loop Detection Function

    RLDP is mainly used on access layer switches for loop detection. (RLDP anti-loop can be used at the distribution
    layer as well, but the protection granularity is relatively large.) RLDP is especially applicable to the detection of self-
    loop of a downlink hub of a switch, which cannot be prevented by STP.

    It is recommended that RLDP be enabled for access switch ports connecting to end users in the project
    implementation phase. The optimized configuration that is deployed in advance can prevent loops on the ports.

    RLDP loop detection mainly applies to the following two scenarios:

    Access Switch

    Access Switch
    Port enabling portfast

    Scenario 1: Switch Self-Loop Scenario 2: Switch Port Self-Loop


    Principle of RLDP Loop Detection

    If a port of a switch configured with RLDP receives an RLDP packet of the switch itself, a loop occurs on the
    port. In this case, RLDP processes the fault according to the user configuration, including generating an
    alarm, setting the port in errdisable state, disabling the port SVI, and disabling port learning and forwarding.

    Actions in case of a loop:


    Switch A
    1. block Logically block the port.
    2. shutdown-port Set the port in errordisable state.
    3. shutdown-svi Disable the port SVI.
    4. Warning Produce a warning.

    RLDP Probe (Switch A) RLDP Probe (Switch A)


    Principle of RLDP One-way Link Detection

    If a one-way link failure occurs, the port link can only receive or send packets, which can be caused by, for
    example, incorrect connection of optical fibers. As shown in the figure below, if an RLDP port receives only
    a probe packet from an adjacent port, a one-way link failure occurs. In this case, RLDP processes the fault
    according to the user configuration.

    Switch A

    RLDP Probe (Switch B) RLDP Probe (Switch A)


    RLDP Notes

    Routed ports do not support the processing method of shutdown-svi. Therefore, the method can be configured but
    will not be executed if a failure is detected on a routed port.

    When loop detection is configured, neighbor devices downlink to a port cannot enable RLDP detection. Otherwise,
    detection on the port will be incorrect.

    If RLDP detects a link failure, a warning is generated. You can configure a log server to record at least three levels
    of device logs.

    Due to different product features, blocked ports of certain products still send packets to the CPU. As a result, if a
    loop is detected on a port and the processing method is configured as block, the port still transmits a large number
    of packets to the CPU. This does not achieve the effect of loop detection. Therefore, it is recommended that the
    shutdown-port processing method be configured for loop detection.

    In RLDP fault processing, the block function and STP are mutually exclusive. If the fault processing method of a
    port is configured as block, it is recommended that STP be disabled. Otherwise, if a one-way link failure occurs,
    which cannot be detected by STP, STP may allow port forwarding while RLDP blocks the port. To enable RLDP
    and STP at the same time, you are advised to configure the fault processing method as shutdown-port.
    Principle of RLDP Two-way Link Detection

    If a two-way link failure occurs, the port link fails to both receive and transmit packets. As shown in the
    figure below, if a device port sends an RLDP probe packet but fails to receive a probe packet and echo
    packet from a neighbor, a two-way link failure occurs.

    Switch A

    RLDP Probe (Switch A)


    Typical Application Scenarios of RLDP

    [Networking requirements] As shown in the figure below, uses from various departments of an enterprise access
    the network through switches A and B. Network loops occur from time to time due to network exceptions caused by
    quality issues of optical fibers interconnecting devices or due to incorrect operations of users.

    RLDP loop detection and one-way and two-way link detection functions need to be configured to rapidly locate
    failures and recover the network in time. Main requirements include:
    o 1. If a one-way or two-way failure is detected on the link between switches A and B, shut down the port.

    o 2. If a loop is detected on a downlink port of switches A and B, block the port.

    o 3. Recover a port five minutes after it is set in errordisable state, and detect all ports that failed the RLDP detection again.

    Switch A Gi0/24 Gi0/24 Switch B

    Gi0/1-20
    Gi0/1-20
    Summary

    RLDP can detect a one-way link failure, two-way link failure, and loop on a switch port, and
    enable different violation actions for detected failures.

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