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Configuring Junos OS for the First Time on a Router or Switch with a Single Routing Engine

1. Connect a terminal or laptop computer to the router through the console port—a serial port on the front of the router. Only console access to the router is enabled by default.
2. Power on the router and wait for it to boot.

   The Junos OS boots automatically. The boot process is complete when you see the login: prompt on the console.

3. Log in as the user root.

   Initially, the root user account requires no password. You can see that you are the root user, because the prompt on the router shows the username root@#.

4. Start the Junos OS command-line interface (CLI):
   root@# cliroot@>
5. Enter Junos OS configuration mode:
   cli> configure[edit]root@#
6. Configure the name of the router (the router hostname). We do not recommend spaces in the router name. However, if the name does include spaces, enclose the entire name in quotation marks ("  ").
   [edit]root@# set system host-name hostname
7. Configure the router’s domain name:
   [edit]root@# set system domain-name domain-name

   Note: Before you begin Step 8, see Supported Routing Engines by Chassis to find the management Ethernet interface that you should use to perform this configuration.

8. 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 devices that use management Ethernet interface fxp0:
     [edit]root@# set interfaces fxp0 unit 0 family inet address address/prefix-length
   • For devices that use management Ethernet interface em0:
     [edit]root@# set interfaces em0 unit 0 family inet address address/prefix-length

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

9. Configure the IP address of a backup or default router. This device is called the backup router, because it 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 only or when the Junos routing software (the routing protocol process, rpd) is not running.

   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.

   [edit]root@# set system backup-router address
10. Configure the IP address of a DNS server. The router uses the DNS name server to translate hostnames into IP addresses.
    [edit]root@# set system name-server address
11. Set the root password, entering either a clear-text password that the system will encrypt, a password that is already encrypted, or an SSH public key string.

    Choose one of the following:

    1. To enter a clear-text password, use the following command:
       [edit]root@# set system root-authentication plain-text-passwordNew password: type passwordRetype new password: retype password
    2. To enter a password that is already encrypted, use the following command:
       [edit]root@# set system root-authentication encrypted-password encrypted-password
    3. To enter an SSH public key, use the following command:
       [edit]root@# set system root-authentication ssh-rsa key
12. Optionally, display the configuration statements:
    [edit]root@ show

    system {host-name hostname;domain-name domain.name;backup-router address;root-authentication {(encrypted-password "password" | public-key);ssh-dsa "public-key";ssh-ecdsa "public-key";ssh-rsa "public-key";}name-server {address;}interfaces {fxp0 {unit 0 {family inet {address address ;}}}}}

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

13. Commit the configuration, which activates the configuration on the router:
    [edit]root@# commit

    After committing the configuration, you see the newly configured hostname appear after the username in the prompt—for example, user@host#.

    The defaults for Junos OS are now set on the router.

    If you want to configure additional Junos OS properties at this time, remain in the CLI configuration mode and add the necessary configuration statements. You need to commit your configuration changes to activate them on the router.

14. Exit from the CLI configuration mode.
    [edit]root@hostname# exitroot@hostname>
15. Back up the configuration on the hard drive.

    After you have installed the software on the router, committed the configuration, and are satisfied that the new configuration is successfully running, you should issue the request system snapshot command to back up the new software to the /altconfig file system. If you do not issue the request system snapshot command, the configuration on the alternate boot device will be out of sync with the configuration on the primary boot device.

    The request system snapshot command causes the root file system to be backed up to /altroot, and /config to be 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 the backup copy of the software are identical.