Configuring Junos OS for the First Time on a Device with Dual Routing Engines

 

If a router has dual Routing Engines, you can create configuration groups and use the same configuration for both Routing Engines. This ensures that the configuration will not change during a failover scenario because of the identical configuration shared between the Routing Engines.

Configure the hostnames and addresses of the two Routing Engines using configuration groups at the [edit groups] hierarchy level. Use the reserved configuration group re0 for the Routing Engine in slot 0 and re1 for the Routing Engine in slot 1 to define Routing Engine-specific parameters. Configuring re0 and re1 groups enables both Routing Engines to use the same configuration file.

Use the apply-groups statement to reproduce the configuration group information in the main part of the configuration.

The commit synchronize command commits the same configuration on both Routing Engines. The command makes the active or applied configuration the same for both Routing Engines with the exception of the groups, re0 being applied to only RE0 and re1 being applied only to RE1. If you do not synchronize the configurations between two Routing Engines and one of them fails, the router may not forward traffic correctly, because the backup Routing Engine may have a different configuration.

To initially configure a router with dual Routing Engines, follow these steps:

  1. Go to Configuring Junos OS for the First Time on a Router or Switch with a Single Routing Engine and follow Step 1 through Step 5 to initially configure the backup Routing Engine.

  2. Create the configuration group re0. The re0 group is a special group designator that is only used by RE0 in a redundant routing platform.
  3. Navigate to the groups re0 level of the configuration hierarchy.
  4. Specify the router hostname.
    Note

    The hostname specified in the router configuration is not used by the DNS server to resolve to the correct IP address. This hostname is used to display the name of the Routing Engine in the CLI. For example, the hostname appears at the command-line prompt when the user is logged in to the CLI:

    Note

    Before you begin Step 5, see Supported Routing Engines by Router to find the management Ethernet interface that you should use to perform this configuration.

  5. Configure the IP address and prefix length for the router management Ethernet interface. The management Ethernet interface provides a separate out-of-band management network for the router.
    • For routers that use management Ethernet interface fxp0:

    • For routers that use management Ethernet interface em0:

      To use em0 as an out-of-band management Ethernet interface, you must configure its logical port, em0.0, with a valid IP address.

  6. Set the loopback interface address for the re0 configuration group:
  7. Return to the top level of the hierarchy.
  8. Create the configuration group re1.
  9. Navigate to the groups re1 level of the configuration hierarchy.
  10. Specify the router hostname.
    Note

    Before you begin Step 11, see Supported Routing Engines by Router to find the management Ethernet interface that you should use to perform this configuration.

  11. Configure the IP address and prefix length for the router management Ethernet interface.
    • For routers that use management Ethernet interface fxp0:

    • For routers that use management Ethernet interface em0:

      To use em0 as an out-of-band management Ethernet interface, you must configure its logical port, em0.0, with a valid IP address.

  12. Set the loopback interface address for re1 configuration group:
  13. Return to the top level of the hierarchy.
  14. Configure the apply-groups statement to reproduce the configuration group information to the main part of the configuration and to specify the group application order.
  15. Configure Routing Engine redundancy:
  16. Save the configuration change on both Routing Engines:

After the configuration changes are saved, complete the management console configuration.

  1. Configure the IP address of the DNS server.
  2. Configure the router domain name:
  3. Configure the IP address of a backup or default router. A backup router is used only while the routing protocol process is not running. Choose a router that is directly connected to the local router by way of the management interface. The router uses this backup router only when it is booting and or when the Junos routing software (the routing protocol process, rpd) is not running. For more information, see Configuring a Backup Router.

    For routers with two Routing Engines, the backup Routing Engine, RE1, uses the backup router as a default gateway after the router boots. This enables you to access the backup Routing Engine. (RE0 is the default master Routing Engine.)

    Note

    The backup router Routing Engine does not support more than 16 destinations. If you configure more than 16 destinations on the backup Routing Engine, the Junos OS ignores any destination addresses after the sixteenth address and displays a commit-time warning message to this effect.

  4. Set the root password by choosing one of the following:
    1. To enter a clear-text password, use the following command:

    2. To enter a password that is already encrypted, use the following command:

    3. To enter an SSH public key, use the following command:

  5. Optionally, display the configuration statements:

    On routers that use management Ethernet interface em0, you will see em0 in place of fxp0 in the show command output.

  6. After you have installed the new software and are satisfied that it is successfully running, issue the request system snapshot command to back up the new software on both master and backup Routing Engines.

    The root file system is backed up to /altroot, and /config is backed up to /altconfig. The root and /config file systems are on the router’s CompactFlash card, and the /altroot and /altconfig file systems are on the router’s hard disk.

    Note

    After you issue the request system snapshot command, you cannot return to the previous version of the software, because the running copy and backup copy of the software are identical.

For information about creating configuration groups, see CLI User Guide.

For information about configuring high availability features for redundant Routing Engine systems and the re0 group, see High Availability Feature Guide.