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OAM Link Fault Management

 

Junos OS allows the Ethernet Interfaces to support the IEEE 802.3ah standard Operation, Administration, and Maintenance (OAM) of Ethernet in access networks. The topics discuss the use of Ethernet OAM link fault management, and its configuration details.

For features on EX Series Switches that require license, see Understanding Software Licenses for EX Series Switches. To understand more about Junos OS Software Licensing, see the Juniper Licensing Guide. Please refer to the product Data Sheets accessible from Products & Services for details, or contact your Juniper Account Team or Juniper Partner.

Juniper Networks Junos operating system (Junos OS) for Juniper Networks allows the Ethernet interfaces on these switches to support the IEEE 802.3ah standard for the Operation, Administration, and Maintenance (OAM) of Ethernet in access networks. The standard defines OAM link fault management (LFM). You can configure IEEE 802.3ah OAM LFM on point-to-point Ethernet links that are connected either directly or through Ethernet repeaters. The IEEE 802.3ah standard meets the requirement for OAM capabilities even as Ethernet moves from being solely an enterprise technology to a WAN and access technology, and the standard remains backward-compatible with existing Ethernet technology.

Ethernet OAM provides the tools that network management software and network managers can use to determine how a network of Ethernet links is functioning. Ethernet OAM should:

  • Rely only on the media access control (MAC) address or virtual LAN identifier for troubleshooting.

  • Work independently of the actual Ethernet transport and function over physical Ethernet ports or a virtual service such as pseudowire.

  • Isolate faults over a flat (or single operator) network architecture or nested or hierarchical (or multiprovider) networks.

The following OAM LFM features are supported:

  • Discovery and Link Monitoring

    The discovery process is triggered automatically when OAM is enabled on the interface. The discovery process permits Ethernet interfaces to discover and monitor the peer on the link if it also supports the IEEE 802.3ah standard. You can specify the discovery mode used for IEEE 802.3ah OAM support. In active mode, the interface discovers and monitors the peer on the link if the peer also supports IEEE 802.3ah OAM functionality. In passive mode, the peer initiates the discovery process. After the discovery process has been initiated, both sides participate in discovery. The switch performs link monitoring by sending periodic OAM protocol data units (PDUs) to advertise OAM mode, configuration, and capabilities.

    You can specify the number of OAM PDUs that an interface can miss before the link between peers is considered down.

  • Remote Fault Detection

    Remote fault detection uses flags and events. Flags are used to convey the following: Link Fault means a loss of signal, Dying Gasp means an unrecoverable condition such as a power failure, and Critical Event means an unspecified vendor-specific critical event. You can specify the periodic OAM PDU sending interval for fault detection. The switch uses the Event Notification OAM PDU to notify the remote OAM device when a problem is detected. You can specify the action to be taken by the system when the configured link-fault event occurs.

  • Remote Loopback Mode

    Remote loopback mode ensures link quality between the switch and a remote peer during installation or troubleshooting. In this mode, when the interface receives a frame that is not an OAM PDU or a pause frame, it sends it back on the same interface on which it was received. The link appears to be in the active state. You can use the returned loopback acknowledgement to test delay, jitter, and throughput.

    Junos OS can place a remote DTE into loopback mode (if remote loopback mode is supported by the remote DTE). When you place a remote DTE into loopback mode, the interface receives the remote loopback request and puts the interface into remote loopback mode. When the interface is in remote loopback mode, all frames except OAM PDUs are looped back without any changes made to the frames. OAM PDUs continue to be sent and processed.

Ethernet OAM link fault management (LFM) can be used for physical link-level fault detection and management. The IEEE 802.3ah LFM works across point-to-point Ethernet links either directly or through repeaters.

To configure Ethernet OAM LFM using the CLI:

  1. Enable IEEE 802.3ah OAM support on an interface:
    [edit protocols oam ethernet link-fault-management]

    user@switch# set interface interface-name
    Note

    You can configure Ethernet OAM LFM on aggregated interfaces.

    Note

    The remaining steps are optional. You can choose which of these features to configure for Ethernet OAM LFM on your switch.

  2. Specify whether the interface or the peer initiates the discovery process by configuring the link discovery mode to active or passive (active = interface initiates; passive = peer initiates):
    [edit protocols oam ethernet link-fault-management]

    user@switch# set interface interface-namelink-discovery active
  3. Configure a periodic OAM PDU-sending interval (in milliseconds) for fault detection:
    [edit protocols oam ethernet link-fault-management]

    user@switch# set interface pdu-intervalinterval
  4. Specify the number of OAM PDUs that an interface can miss before the link between peers is considered down:
    [edit protocols oam ethernet link-fault-management]

    user@switch# set interface interface-name pdu-threshold threshold-value
  5. Configure event threshold values on an interface for the local errors that trigger the sending of link event TLVs:

    • Set the threshold value (in seconds) for sending frame-error events or taking the action specified in the action profile:

      [edit protocols oam ethernet link-fault-management]

      user@switch# set interface interface-name event-thresholds frame-error count

    • Set the threshold value (in seconds) for sending frame-period events or taking the action specified in the action profile:

      [edit protocols oam ethernet link-fault-management]

      user@switch# set interface interface-name event-thresholds frame-period count


    • Set the threshold value (in seconds) for sending frame-period-summary events or taking the action specified in the action profile:

      [edit protocols oam ethernet link-fault-management]

      user@switch# set interface interface-name event-thresholds frame-period-summary count

    • Set the threshold value (in seconds) for sending symbol-period events or taking the action specified in the action profile:

      [edit protocols oam ethernet link-fault-management]

      user@switch# set interface interface-name event-thresholds symbol-period count
    Note

    You can disable the sending of link event TLVs.

    To disable the sending of link event TLVs:

    [edit protocols oam ethernet link-fault-management]

    user@switch# set interface interface-name negotiation-options no-allow-link-events
  6. Create an action profile to define event fault flags and thresholds to be taken when the link fault event occurs. Then apply the action profile to one or more interfaces. (You can also apply multiple action profiles to a single interface.)
    1. Name the action profile:
      [edit protocols oam ethernet link-fault-management]

      user@switch# set action-profile profile-name
    2. Specify actions to be taken by the system when the link fault event occurs:
      [edit protocols oam ethernet link-fault-management]

      user@switch# set action-profile profile-name action syslog
      user@switch# set action-profile profile-name action link-down
    3. Specify events for the action profile:
      [edit protocols oam ethernet link-fault-management]

      user@switch# set action-profile profile-name event link-adjacency-loss
    Note

    For each action profile, you must specify at least one link event and one action. The actions are taken only when all of the events in the action profile are true. If more than one action is specified, all actions are executed. You can set a low threshold for a specific action such as logging the error and set a high threshold for another action such as system logging.

  7. Set a remote interface into loopback mode so that all frames except OAM PDUs are looped back without any changes made to the frames. Set the remote DTE in loopback mode (the remote DTE must support remote-loopback mode) and then enable remote loopback support for the local interface.
    [edit protocols oam ethernet link-fault-management]

    user@switch# set interface interface-name remote-loopback
    user@switch# set interface interface-name negotiation-options allow-remote-loopback

Junos OS allows the Ethernet interfaces on these switches to support the IEEE 802.3ah standard for the Operation, Administration, and Maintenance (OAM) of Ethernet in access networks. The standard defines OAM link fault management (LFM). You can configure IEEE 802.3ah OAM LFM on point-to-point Ethernet links that are connected either directly or through Ethernet repeaters.

This example describes how to enable and configure OAM LFM on a Gigabit Ethernet interface:

Requirements

This example uses the following hardware and software components:

  • Junos OS Release 9.4 or later for EX Series switches

  • Two EX3200 or EX4200 switches connected directly

Overview and Topology

Junos OS switches allows the Ethernet interfaces on these switches to support the IEEE 802.3ah standard for the Operation, Administration, and Maintenance (OAM) of Ethernet in access networks. The standard defines OAM link fault management (LFM). You can configure IEEE 802.3ah OAM LFM on point-to-point Ethernet links that are connected either directly or through Ethernet repeaters.

This example uses two EX4200 switches connected directly. Before you begin configuring Ethernet OAM LFM on two switches, connect the two switches directly through a trunk interface.

Configuring Ethernet OAM Link Fault Management on Switch 1

CLI Quick Configuration

To quickly configure Ethernet OAM LFM, copy the following commands and paste them into the switch terminal window:

[edit protocols oam ethernet link-fault-management]

set interface ge-0/0/0

set interface ge-0/0/0 link-discovery active

set interface ge-0/0/0 pdu-interval 800

set interface ge-0/0/0 remote-loopback

Step-by-Step Procedure

To configure Ethernet OAM LFM on switch 1:

  1. Enable IEEE 802.3ah OAM support on an interface:
    [edit protocols oam ethernet link-fault-management]

    user@switch1# set interface ge-0/0/0


  2. Specify that the interface initiates the discovery process by configuring the link discovery mode to active:
    [edit protocols oam ethernet link-fault-management]

    user@switch1# set interface ge-0/0/0 link-discovery active


  3. Set the periodic OAM PDU-sending interval (in milliseconds) to 800 on switch 1:
    [edit protocols oam ethernet link-fault-management]

    user@switch1# set interface pdu-interval 800


  4. Set a remote interface into loopback mode so that all frames except OAM PDUs are looped back without any changes made to the frames. Ensure that the remote DTE supports remote loopback mode. To set the remote DTE in loopback mode
    [edit protocols oam ethernet link-fault-management]

    user@switch1# set interface ge-0/0/0.0 remote-loopback

Results

Check the results of the configuration:

[edit]


user@switch1# show

Configuring Ethernet OAM Link Fault Management on Switch 2

CLI Quick Configuration

To quickly configure Ethernet OAM LFM on switch 2, copy the following commands and paste them into the switch terminal window:

[edit protocols oam ethernet link-fault-management ]

set interface ge-0/0/1

set interface ge-0/0/1 negotiation-options allow-remote-loopback

Step-by-Step Procedure

To configure Ethernet OAM LFM on switch 2:

  1. Enable OAM on the peer interface on switch 2:
    [edit protocols oam ethernet link-fault-management]

    user@switch2# set interface ge-0/0/1


  2. Enable remote loopback support for the local interface:
    [edit protocols oam ethernet link-fault-management]

    user@switch2# set interface ge-0/0/1 negotiation-options allow-remote-loopback

Results

Check the results of the configuration:

Verification

Verifying That OAM LFM Has Been Configured Properly

Purpose

Verify that OAM LFM has been configured properly.

Action

Use the show oam ethernet link-fault-management command:

Sample Output

Meaning

When the output displays the MAC address and the discover state is Send Any, it means that OAM LFM has been configured properly.