Manually Configuring Master and Backup Routing Engines

For routers with two Routing Engines, you can configure which Routing Engine is the master and which is the backup. By default, the Routing Engine in slot 0 is the master (RE0) and the one in slot 1 is the backup (RE1).

To modify the default configuration, include the routing-engine statement at the [edit chassis redundancy] hierarchy level:

[edit chassis redundancy]

routing-engine slot-number (master | backup | disabled);

slot-number can be 0 or 1. To configure the Routing Engine to be the master, specify the master option. To configure it to be the backup, specify the backup option. To switch between the master and the backup Routing Engines, you must modify the configuration and then activate it by issuing the commit command.

The running state of a Routing Engine (master, backup, or disabled) is determined by mastership election upon system boot.

• Master—If a Routing Engine is configured as master, it has full functionality. It receives and transmits routing information, builds and maintains routing tables, communicates with interfaces and Packet Forwarding Engine components, and has full control over the chassis. Once a Routing Engine becomes master, it resets the switch plane (SSB, SCB, and SFM) and downloads its current version of the microkernel to the Packet Forwarding Engine components, guaranteeing software compatibility.
• Backup—If a Routing Engine is configured to be the backup, it does not maintain routing tables or communicate with Packet Forwarding Engine or chassis components. However, it runs through its memory check and boot sequence to the point of displaying a login prompt. A backup Routing Engine supports full management access through the Ethernet, console, and auxiliary ports, and can communicate with the master Routing Engine. Additionally, a backup Routing Engine responds to the Routing Engine request chassis routing-engine master switch command. The backup Routing Engine maintains a connection with the master Routing Engine and monitors the master Routing Engine. If the connection is broken, you can switch mastership by entering the switchover command. If the master Routing Engine is hot-swapped out of the system, the backup takes over control of the system as the new master Routing Engine. Once a Routing Engine becomes master, it resets the switch plane and downloads its own version of the microkernel to the Packet Forwarding Engine components.
• Disabled—A disabled Routing Engine has progressed through its memory check and boot sequence to the point of displaying a login prompt (similar to backup state) but does not respond to a request chassis routing-engine master switch command. A Routing Engine in disabled state supports full management access through the Ethernet, console, and auxiliary ports, and can communicate with the master Routing Engine. A disabled Routing Engine does not participate in a mastership election. To move from disabled state to backup state, the Routing Engine must be reconfigured to be the backup Routing Engine.

Action

To configure RE1 to be the default master, issue the following CLI command in configuration mode at the [edit] hierarchy level:

For slot 0:

[edit]

user@host# set chassis redundancy routing-engine 1 master

[edit]

user@host# commit

For slot 1:

[edit]

user@host# set chassis redundancy routing-engine 0 backup 

[edit]

user@host# commit 

Action

To view the Routing Engine mastership/backup status, use the following CLI command in operational mode:

user@host> show chassis routing-engine

Sample Output

user@host> show chassis routing-engine

Routing Engine status:

  Slot 0:

    Current state                  Backup

    Election priority              Backup (default)

    Temperature                 26 degrees C / 78 degrees F

    DRAM                      2048 MB

    Memory utilization          12 percent

    CPU utilization:

      User                       0 percent

      Background                 0 percent

      Kernel                     1 percent

      Interrupt                  0 percent

      Idle                      99 percent

    Serial ID                      210929000142

    Start time                     2004-05-12 13:14:30 PDT

    Uptime                        5 days, 22 hours, 7 minutes, 9 seconds

    Load averages:                 1 minute   5 minute  15 minute

                                       0.07       0.02       0.00

Routing Engine status:

  Slot 1:

    Current state                  Master

    Election priority              Master (default)

    Temperature                 27 degrees C / 80 degrees F

    DRAM                      2048 MB

    Memory utilization          13 percent

    CPU utilization:

      User                       0 percent

      Background                 0 percent

      Kernel                     0 percent

      Interrupt                  0 percent

      Idle                     100 percent

    Serial ID                      210929000143

    Start time                     2004-04-05 17:08:41 PDT

    Uptime                        42 days, 18 hours, 12 minutes, 45 seconds

What It Means

Each Routing Engine only checks its own configuration. Therefore, you must configure the redundancy settings on both Routing Engines correctly for the system to operate properly.

If both Routing Engines are configured as master, whichever Routing Engine comes up first will be the master. When the second Routing Engine comes up, it will try to assume mastership. However, the current master Routing Engine will reject this request, and the second Routing Engine will become the backup.

If both Routing Engines are configured as backup and come up after bootup, neither Routing Engine becomes master. The only way for either to become master is if one of the host module components (such as the Routing Engine) is physically removed, or if a Routing Engine has failover on-loss-of-keepalives configured and the connection between Routing Engines is interrupted for a period of time. The resulting timeout due to a loss of keepalives will force one of the Routing Engines to become the master. See Configuring the Backup Routing Engine to Assume Mastership on Failure of Keepalives for more information.