The ‘admin down’ state is caused by the ‘disable’ configuration statement under the interface. The ‘delete interfaces ge-0/0/0 disable’ command removes this configuration, allowing the interface to become operational. The ‘set interfaces ge-0/0/0 disable’ command would keep it down, ‘activate’ is not a valid operational command for this purpose, and ‘commit confirmed’ is for committing changes with a rollback timer.

The ‘show system information’ command is specifically designed to display a summary including the hostname, model, Junos version, serial number, and system uptime. ‘show version’ shows the Junos version but not the serial or uptime. ‘show chassis hardware’ provides detailed hardware inventory but is less concise. ‘show system uptime’ only shows the uptime.

Junos automatically saves the last 50 committed configurations as rollback files (0 being the most recent). ‘Rollback 1’ loads the configuration from one commit prior, and ‘commit’ makes it active. This is the fastest and most reliable method. Manual deletion is error-prone, ‘load override’ requires a saved file, and rebooting is disruptive and unnecessary.

In Junos, the suffix following the dot (.) on an interface name (e.g., ge-0/0/1.0) denotes the logical unit number. This unit is where Layer 3 configuration like IP addresses, VLAN tagging, and family inet are applied. It is not related to physical hardware numbering or software versions.

In Junos, Layer 3 configuration must be applied to a logical unit (typically unit 0). The correct hierarchy is `set interfaces ge-0/0/0 unit 0 family inet address 192.168.1.1/24`. The configuration shown attempts to apply the address directly to the physical interface, which is not valid.

The Junos configuration model uses a candidate configuration. Changes are made in this temporary file. The ‘commit’ command validates the syntax and, if successful, copies the candidate configuration to become the new active/running configuration. It does not require a separate save step for activation.

For secure, remote out-of-band management, you must have: 1) An IP address on the dedicated management interface (fxp0 on older devices, em0, vme0, or mgmt on newer ones) to establish reachability, and 2) A root authentication method (password or SSH key) to permit login. Telnet is insecure and should not be used. A default gateway is only needed if the management network is outside the local subnet.

In Junos, ‘preference’ is equivalent to Administrative Distance in other vendors’ terminology. It indicates the trustworthiness of a routing source. A lower value is more trusted. A directly connected route (preference 0) is the most trusted. An OSPF internal route (preference 10) is trusted less than a direct route, so the direct route will be installed in the forwarding table if for the same prefix.

The ‘from’ field in the ‘show system users’ output indicates the source of the connection. ‘console’ specifically means the session is established through the physical serial console port on the device. ‘super-user’ is the login class, indicating privilege level, but the key identifier of the connection method is ‘console’.

The ‘admin down’ state is caused by the ‘disable’ configuration statement under the interface. The ‘delete interfaces ge-0/0/0 disable’ command removes this configuration, allowing the interface to become operational. The ‘set interfaces ge-0/0/0 disable’ command would keep it down, ‘activate’ is not a valid operational command for this purpose, and ‘commit confirmed’ is for committing changes with a rollback timer.0