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Configuring Junos OS on the EX9251

EX9251 Switch Default Configuration

Each EX9251 switch is programmed with a factory default configuration that contains the values set for each configuration parameter when a switch is shipped. The default configuration file sets values for system parameters such as the system log and file messages.

When you commit changes to the configuration, a new configuration file is created that becomes the active configuration. You can always revert to the factory default configuration. See Reverting to the Default Factory Configuration for the EX Series Switch.

This topic shows the factory default configuration file of an EX9251 switch:

Connecting and Configuring an EX9251 Switch (CLI Procedure)

Before you begin connecting and configuring an EX9251 switch, gather the following information:

  • Name the switch will use on the network

  • Domain name the switch will use

  • IP address and prefix length information for the Ethernet interface

  • IP address of a default switch

  • IP address of a DNS server

  • Password for the root user

The EX9251 switch is shipped with the Junos OS preinstalled and ready to be configured when the switch is powered on. There are two 16-MB internal NAND Flash memory devices located on the baseboard for BIOS storage. You can insert the USB storage device into the USB slot on the front panel. The switch also has two built-in M.2-based solid-state drives (SSDs) (labeled SSD0 and SSD1). There are three copies of the software: one each on the SSD drives and one on a USB flash drive that can be inserted into the slot in the faceplate of the RE module.

When the switch boots, it first attempts to start the image on the USB flash drive. If there is no USB flash drive installed or if the attempt otherwise fails, the switch next attempts to start the software from the SSD installed in slot SSD0, and finally from the SSD installed in slot SSD1.

You configure the switch by issuing Junos OS command-line interface (CLI) commands, either on a console device attached to the console (CON) port on the front panel, or over a telnet connection to a network connected to the Ethernet management (MGMT) port on the front panel.

This procedure connects the switch to the network, but does not enable it to forward traffic. For complete information about enabling the switch to forward traffic, including examples, see the Junos OS configuration guides.

To configure the software:

  1. Verify that the switch is powered on.
  2. Log in as the root user. There is no password.
  3. Start the CLI.
  4. Enter configuration mode.
  5. Set the root authentication password by entering either a clear-text password, an encrypted password, or an SSH public key string (DSA or RSA).




  6. Configure the name of the switch. If the name includes spaces, enclose the name in double quotation marks (“ ”).
  7. Create a user account.
  8. Set the user account class to super-user.
  9. Configure the switch’s domain name.
  10. Configure the IP address and prefix length for the switch’s Ethernet interface.
  11. Configure the IP address of a backup router, which is used only while the routing protocol is not running.
  12. Configure the IP address of a DNS server.
  13. (Optional) Configure the static routes to remote subnets with access to the management port. Access to the management port is limited to the local subnet. For more information about static routes, see the Junos OS Administration Library for Routing Devices.
  14. Configure the telnet service at the [edit system services] hierarchy level.
  15. (Optional) Display the configuration to verify that it is correct.
  16. Commit the configuration to activate it on the switch.
  17. (Optional) Configure additional properties by adding the necessary configuration statements. Then commit the changes to activate them on the switch.
  18. When you have finished configuring the switch, exit configuration mode.

Ensure that the removable storage media that contains a copy of Junos OS is not installed in the switch except when you want to install Junos OS from the storage media. If the storage media is installed during normal operation and if the switch is rebooted intentionally or accidentally (for example, as a result of a power outage), the configuration in the switch is deleted and the copy of the software in the storage media is installed in the switch.