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Maintaining MX104 Host Subsystem Components

 

Maintaining the MX104 Routing Engines

Purpose

For optimum router performance, verify the condition of the Routing Engines.

Action

On a regular basis:

  • Check the Routing Engine LEDs. For more information about the LEDs and the display, see MX104 Routing Engine Overview.

  • Issue the show chassis routing-engine command to check the status of the Routing Engines. The output is similar to the following:

    user@host> show chassis routing-engine

Meaning

The command output displays the Routing Engine slot number, current state (Master, Backup, or Disabled), election priority (Master or Backup), and airflow temperature. The command output also displays the total DRAM available to the Routing Engine processor, the CPU utilization percentage, and the Routing Engine serial number for the slot. Additionally, the command output displays when the Routing Engine started running, how long the Routing Engine has been running, and the time, uptime, and load averages for the last 1, 5, and 15 minutes.

Check the Uptime to ensure that the Routing Engine has not rebooted since it started running.

To check the Routing Engine environmental status information, such as the operating state, function, and operating temperature, use the show chassis environment routing-engine command:

user@host> show chassis environment routing-engine

For further description of the output from the command, see the show chassis routing-engine command summary in the CLI Explorer.

Replacing an MX104 Routing Engine

Effect of Taking the MX104 Routing Engine Offline

Before you replace a Routing Engine, you must take the Routing Engine offline. The Routing Engine is hot-pluggable.

Normally, if two Routing Engines are installed in the router, RE 0 functions as the master and RE 1 functions as the backup. You can remove the backup Routing Engine (or either of its components) without interrupting the functioning of the router. If you take the master Routing Engine offline, the backup Routing Engine becomes the master (the router might reboot, depending on your configuration). If the router has only one Routing Engine, taking the Routing Engine offline causes the router to shut down. The effect of taking the master Routing Engine offline varies depending on your configuration of high availability features.

Table 1 explains the effect of taking the Routing Engine offline.

Table 1: Effect of Taking the Routing Engine Offline

Type of Routing Engine

Effect of Taking the Routing Engine Offline

Nonredundant Routing Engine

The router shuts down.

Backup Routing Engine

The functioning of the router is not interrupted. The backup Routing Engine is hot-removable and hot-insertable.

Master Routing Engine

The backup Routing Engine becomes the master. The backup Routing Engine assumes Routing Engine functions. The master Routing Engine is hot-pluggable. Removal or failure of the master Routing Engine affects forwarding and routing based on the high availability configuration:

  • Dual Routing Engines without any high availability features enabled—Traffic is interrupted while the Packet Forwarding Engine is reinitialized. All kernel and forwarding processes are restarted. When the switchover to the new master Routing Engine is complete, routing convergence takes place and traffic is resumed.

  • Graceful Routing Engine switchover (GRES) is enabled—Graceful Routing Engine switchover preserves interface and kernel information. Traffic is not interrupted. However, graceful Routing Engine switchover does not preserve the control plane. Neighboring routers detect that the router has restarted and react to the event in a manner prescribed by individual routing protocol specifications. To preserve routing without interruption during a switchover, graceful Routing Engine switchover must be combined with nonstop active routing.

  • Nonstop active routing is enabled (graceful Routing Engine switchover must be configured for nonstop active routing to be enabled)—Nonstop active routing supports Routing Engine switchover without alerting peer nodes that a change has occurred. Nonstop active routing uses the same infrastructure as graceful Routing Engine switchover to preserve interface and kernel information. However, nonstop active routing also preserves routing information and protocol sessions by running the routing protocol process (rpd) on both Routing Engines. In addition, nonstop active routing preserves TCP connections maintained in the kernel.

  • Graceful restart is configured—Graceful restart provides extensions to routing protocols so that neighboring helper routers restore routing information to a restarting router. These extensions signal neighboring routers about the graceful restart and prevent the neighbors from reacting to the router restart and from propagating the change in state to the network during the graceful restart period. Neighbors provide the routing information that enables the restarting router to stop and restart routing protocols without causing network reconvergence. Neighbors are required to support graceful restart. The routing protocol process (rpd) restarts. A graceful restart interval is required. For certain protocols, a significant change in the network can cause graceful restart to stop.

Note

Router performance might change if the backup Routing Engine's configuration differs from the former master's configuration. For the most predictable performance, configure the two Routing Engines identically, except for parameters unique to each Routing Engine.

To configure Routing Engine-specific parameters and still use the same configuration on both Routing Engines, include the appropriate configuration statements under the re0 and re1 statements at the [edit groups] hierarchy level and use the apply-groups statement. For instructions, see the Junos OS Administration Library.

To configure Routing Engine-specific parameters and still use the same configuration on both Routing Engines, include the appropriate configuration statements under the re0 and re1 statements at the [edit groups] hierarchy level and use the apply-groups statement. For instructions, see the Junos OS Administration Library.

Note

For information about configuring graceful Routing Engine switchover, graceful restart, and nonstop active routing, see the High Availability Feature Guide.

Note

Graceful restart software requirements depend on the routing protocols configured on the router. For the minimum software requirements for graceful restart, see the High Availability Feature Guide.

Taking an MX104 Routing Engine Offline

Before you take a Routing Engine offline, see Effect of Taking the MX104 Routing Engine Offline.

To take the Routing Engine offline:

  1. Determine whether the Routing Engine is functioning as the master or as the backup, using one of the two following methods:
    • If the MASTER LED on the Routing Engine is lit, that Routing Engine is functioning as the master.

    • Issue the show chassis routing-engine command.

      user@host> show chassis routing-engine

      The master Routing Engine is designated Master in the current state field.

  2. If the Routing Engine is functioning as the master, switch it to backup using the request chassis routing-engine master switch command:
    user@host> request chassis routing-engine master switch
  3. On the console or other management device connected to the Routing Engine you are removing, enter CLI operational mode and issue the request system halt command. The command shuts down the Routing Engine cleanly, so its state information is preserved:
    user@host> request system halt

    Wait until a message appears on the console confirming that the operating system has halted.

    For more information about the command, see the CLI Explorer.

    Note

    The SCB might continue forwarding traffic for approximately five minutes after the request system halt command has been issued.

Removing an MX104 Routing Engine

Before you remove a Routing Engine, remove the cables that connect to it.

Caution

Before you replace a Routing Engine, you must take the Routing Engine offline. If there is only one Routing Engine, taking the Routing Engine offline shuts down the router.

Caution

If the Routing Engine to be replaced is currently functioning as the master Routing engine, switch it to be the backup before removing it.

To remove a Routing Engine from (see Figure 1):

  1. Take the Routing Engine offline gracefully.
  2. Place an electrostatic bag or antistatic mat on a flat, stable surface.
  3. Attach an ESD grounding strap to your bare wrist and connect the strap to one of the ESD points on the chassis.
  4. Verify that the Routing Engine LEDs are off.
  5. Loosen the captive screws on both sides of the Routing Engine.
  6. Grasp the Routing Engine by the captive screws, and slide it about halfway out of the chassis.
  7. Place one hand underneath the Routing Engine to support it, and slide it completely out of the chassis.
  8. Place the Routing Engine on the antistatic mat.Note

    To maintain proper airflow through the chassis, do not leave the chassis without a Routing Engine for extended periods of time. If a Routing Engine is removed, a replacement Routing Engine should be installed as soon as possible.

Figure 1: Removing an MX104 Routing Engine
Removing an MX104 Routing
Engine

Installing an MX104 Routing Engine

To install a Routing Engine (see Figure 2):

  1. Attach an ESD grounding strap to your bare wrist and connect the strap to one of the ESD points on the chassis.
  2. Place one hand underneath the Routing Engine to support it.
  3. Carefully align the sides of the Routing Engine with the guides inside the opening on the chassis.
  4. Slide the Routing Engine into the chassis until you feel resistance.
  5. Tighten the captive screws on both sides of the Routing Engine.
  6. Connect the management device cables to the Routing Engine. Note

    The Routing Engine might require several minutes to boot.

  7. After the Routing Engine boots, verify that it is installed correctly:
    • Check the LEDs on the Routing Engine. If the router is operational and the Routing Engine is functioning properly, the green ONLINE LED lights steadily. If the red OK/FAIL LED lights steadily instead, remove and install the Routing Engine again. If the red OK/FAIL LED still lights steadily, the Routing Engine is not functioning properly. Contact your customer support representative.

    • Check the status of the Routing Engine, using the show chassis environment routing-engine CLI command:

      user@ host > show chassis environment routing-engine

      If the router is operational and the Routing Engine is functioning properly, the state shows Online Master or Online Standby. For more information about using the show chassis routing-engine CLI command, see show chassis environment routing-engine.

Figure 2: Installing a Routing Engine
Installing a Routing Engine