What You Need to Know about Junos Command Hierarchy
All the Junos OS commands are split between operational and configuration mode. Yet, each mode still has hundreds of possible commands. If the command line interface (CLI) showed them all in a single list, it would fill many screens and be difficult to use. So the Junos OS software arranges them into hierarchies that group together related commands.
Among the most commonly used of the operational hierarchies are the show and clear commands. You use the show command to display status and statistics for just about everything on the device, from the network interfaces (show interfaces) to the hardware (show chassis hardware) to the routing protocols (show ospf, show bgp, and so on). You use the clear command to clear, or zero, statistics collected by the device.
In the hierarchies under the clear and show commands of the operational mode, both top-level commands have bgp, interfaces, and system commands. Then the next level down has different options in the hierarchies. From these hierarchies, some of the commands available are clear bgp neighbor neighbor-name, show bgp neighbor neighbor-name, and show interfaces.
When you first log in to the device, you are in operational mode. By typing a ? at the command prompt, you can view a list of all the top-level operational commands for your device. A subset of the operational mode command hierarchy, where the command name is on the left and a description is on the right, follows:
wiley@netnik> ? Possible completions: clear Clear information in the system configure Manipulate software configuration information file Perform file operations help Provide help information monitor Show real-time debugging information ping Ping remote target quit Exit the management session request Make system-level requests restart Restart software process set Set CLI properties, date/time, craft interface message show Show system information ssh Start secure shell on another host telnet Telnet to another host traceroute Trace route to remote host
If you have experience using Cisco IOS software, know that Junos does not use the keyword IP in its commands. Many of the operations commands are otherwise the same. For example, the IOS command show ip route becomes show route in Junos.
If you peek under each command, you see the next level in the hierarchy. For example, this is a truncated list of the different varieties of the show commands.
wiley@netnik> show ? Possible completions: accounting Show accounting profiles and records aps Show Automatic Protection Switching information arp Show system Address Resolution Protocol table entries as-path Show table of known autonomous system paths bfd Show Bidirectional Forwarding Detection information bgp Show Border Gateway Protocol information chassis Show chassis information class-of-service Show class-of-service (CoS) information cli Show command-line interface settings configuration Show current configuration
Using ? allows you to see the subordinate commands in the next level of the hierarchy. Drill down one more level of the hierarchy, into the show chassis hierarchy, and you see
wiley@netnik> show chassis ? Possible completions: alarms Show alarm status environment Show component status, temperature, cooling system speeds firmware Show firmware and operating system version for components fpc Show Flexible PIC Concentrator status hardware Show installed hardware components location Show physical location of chassis mac-addresses Show media access control addresses pic Show Physical Interface Card state, type, and uptime routing-engine Show Routing Engine status
The hierarchy for a command ends when you see Enter as one of the possible command completions.
wiley@netnik> show chassis hardware ? Possible completions: <[Enter]> Execute this command detail Include RAM and disk information in output extensive Display ID EEPROM information models Display serial number and model number for orderable FRUs | Pipe through a command
So, when you finally reach the end of the hierarchy, press Enter to see output data.
wiley@netnik> show chassis hardware Hardware inventory: Item Version Part number Serial number Description Chassis 25708 M20 Backplane REV 03 710-002334 BB9738 M20 Backplane Power Supply A REV 06 740-001465 005234 AC Power Supply Display REV 04 710-001519 BA4681 M20 FPM Board Routing Engine 0 REV 06 740-003239 1000224893 RE-2.0 Routing Engine 1 REV 06 740-003239 9000022146 RE-2.0 SSB 0 REV 02 710-001951 AZ8112 Internet Processor IIv1 SSB 1 N/A N/A N/A Backup FPC 0 REV 03 710-003308 BD8455 E-FPC PIC 0 REV 08 750-002303 AZ5310 4x F/E, 100 BASE-TX PIC 1 REV 07 750-004745 BC9368 2x CT3-NxDS0 PIC 2 REV 03 750-002965 HC9279 4x CT3 Fan Tray 0 Front Upper Fan Tray Fan Tray 1 Front Middle Fan Tray Fan Tray 2 Front Bottom Fan Tray Fan Tray 3 Rear Fan Tray
The output of the show commands in operational mode is different from the output of the show commands in configuration mode. Operational mode has a large group of show commands to display status and statistics for just about everything on the device. In configuration mode the command outputs a listing of the candidate configuration.