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Boot Process for Routers with VM Host Support

The boot process involves configuring the basic parameters through the console port and filename synchronization.

Booting for the First Time

When you power on a device for the first time, the router initiates the boot process.

After hardware and field-programmable gate array (FPGA) level initialization is complete, the Unified Extensible Firmware Interface (UEFI) selects the boot device to launch the host OS. The host OS launches the default guest Junos OS, which is the administrative context for the user. After the device has powered on completely, a login prompt is displayed on the console port.

Boot Sequence

The Routing Engine boots from the storage media in the following sequence:

  • USB

  • Solid-state Drive 1 (SSD1)

  • Solid-state Drive 1 (SSD2)

  • Preboot Execution Environment (PXÈ)

Understanding Console Port

To perform the initial configuration, you need to connect a terminal or laptop computer to the router through the console port, which is a serial port on the front of the router. The console port is the management port used by administrators to log in to Junos OS directly—that is, without using a network connection.

Two universal asynchronous receiver/transmitter (UART) ports are connected to the midplane to provide CTY access to line cards. At any time, two ports can be active for the CTY application. These ports are available to the Junos VMs for configuration.

For more information about configuring the router’s basic properties, see Accessing a Junos OS Device the First Time.

Understanding Hostnames Synchronization

A hostname provides a unique identification for a router on the network. Junos OS uses the configured hostname as part of the command prompt, to prepend log files and other accounting information, as well as in other places where knowing the device identity is useful. Although Junos OS supports a maximum hostname length of 255 characters, the host OS supports hostnames that have only 64 characters or less. Therefore, hostnames need to be synchronized between Junos OS and the host OS. Keep in mind the following conditions when you synchronize the hostname configured on Junos OS with that on the host OS:

  • If the Junos OS-configured hostname has less than or equal to 58 characters, then the hostname supported by the host OS (Linux) has the format Junos hostname-node.

    For example, if the Junos OS-configured hostname is xx..xx, the hostname is xx..xx-node.

  • If the Junos OS-configured hostname is greater than 58 characters in length, then the synchronization process truncates characters from the 59th character onward and replaces the truncated characters with -node.

Related Documentation