This white paper provides a clear introduction to the workings of the Junos operating system and the devices in the Junos lineup. Following the outline of the Introduction to the Junos Operating System course, we will focus on topics that will get your feet wet and have you talking Junos in no time.
None of us have much time to waste, so what can you do when your environment changes quickly and you need to come up to speed on a device that you have never seen before? You find the quickest way to bring yourself up to speed. This white paper will help you do just that by providing a clear introduction to the workings of the Junos operating system and the devices in the Junos lineup. The white paper follows the outline of the Introduction to the Junos Operating System Student Guide used in the Global Knowledge course.
Some of you will have experience with other vendors' equipment, and some of you will not have much experience at all; therefore, we will focus on topics that will get your feet wet the quickest and have you talking Junos in no time.
The core of Juniper devices is the Junos OS. Junos OS is based on the FreeBSD UNIX operating system (OS). The OS implements a single software train through the entire line of Junos products. The same train is used from the entry-level J series routers to the service provider TX Matrix switches. Each product line implements the same base OS, but each has additional code specific to that product line.
To create stable devices that can deliver high performance you need to adhere to sound logic and strict processes. Juniper has done this by keeping a clean separation between the control and forwarding planes on their devices. The control plane includes the routing engine and forwarding table. The forwarding table is linked to the packet-forwarding engine of the forwarding plane, allowing for stable control protocols and high speed forwarding capabilities. The forwarding plane is responsible for the other functions like policing, stateless firewall filtering, and class of service. Transit traffic is forwarded via the Packet Forwarding Engine without passing through the control plane. This is possible because the control plane updates the forwarding table for the forwarding plane. The exception traffic, traffic destined to the local device, is sent to the routing engine CPU.
There are three types of devices: switching, routing, and security. The smallest routing platform is the J Series routers, which are ideal for remote, branch, and regional offices. The M Series Multiservice Routers are ideal for enterprise and service provider networks. The T Series Core Routers are ideal for service provider networks. On the switching side, the EX Series Ethernet Switches are ideal for regional offices, campuses, and data centers. The MX Series Ethernet Services Routers are ideal for carrier Ethernet environments.
The original Junos product line lacked one product to compete in the enterprise arena, a security device. Juniper acquired Netscreen to initially bridge this gap with the Netscreen Screen OS devices, but the bigger picture was to manufacture a Juniper security device using the Junos OS. With this as the goal, Juniper introduced their first security appliance called the SRX Services Gateways. The SRX devices are ideal for enterprise and service provider networks.
You have the same access options that most other vendors provide; you can connect via console, telnet, and SSH to use the CLI interface. GUI access via HTPP is also available, but most people find that the CLI is much easier and quicker to use than the GUI.
Junos has the capability for a user to automatically login to the UNIX BSD shell just like you would normally with a Linux or UNIX device. For example, if you login as root, you will be placed into the UNIX BSD shell. You can't perform any switching, routing, or security functions from the BSD shell. You must switch to operation mode where you can display statistics and configuration information.
The UNIX BSD shell is designated with the % prompt. Here you can enter standard UNIX commands.
root@%
You can enter operation mode by typing cli and pressing enter. Operational mode is designated with the > prompt. Once you're in operation mode, you can utilize operational commands, and you can enter configuration mode from here.
root@% cli
root>
Once you're in operation mode, you will see that Junos uses a hierarchical system to arrange its commands. This is even more apparent in configuration mode.
Entering configure or edit at the operational prompt will place you in configuration mode. Configuration mode is designated with the # prompt. You will also notice that the word edit appears above the prompt in brackets. This shows your level in the command hierarchy and it will change as you change levels.
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