Juniper Junos Fundamentals
Junos OS is the network operating system you use to configure, monitor, and troubleshoot many Juniper routers, switches, and security devices. Its CLI separates operational checks from staged configuration changes that take effect when you commit them.
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Intro
Juniper Junos Fundamentals
Junos OS gives you one operating model for many Juniper network devices. You use it to inspect device state, define configuration, and control how routes reach the forwarding hardware.
The central idea is separation. The Routing Engine runs control and management processes. The Packet Forwarding Engine moves packets between interfaces. The Routing Engine selects active routes and supplies a forwarding table to the Packet Forwarding Engine.
This split helps you reason about a fault. A routing protocol can fail to learn a route in the control plane. A learned route can fail to become active. An active route can fail to reach the forwarding table. Packets can still fail because an interface or next hop is unavailable. Each stage needs a different check.
Two CLI modes
Operational mode answers, “What is the device doing?” Its prompt ends with >. Commands such as show, ping, and traceroute display state or test connectivity.
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Sources
- https://www.juniper.net/documentation/us/en/software/junos/cli/topics/topic-map/getting-started.html
Supports
- Operational and configuration mode prompts
- Entering configuration mode and running operational commands from it
- Context-sensitive help and basic show commands
- Loading and committing rollback configurations
- https://www.juniper.net/documentation/us/en/software/junos/cli/topics/topic-map/cli-overview.html
Supports
- CLI purpose and its two modes
- Hierarchical configuration statements
- Candidate and active configuration separation
- Commit activation boundary
- NETCONF as another monitoring and configuration tool
- https://www.juniper.net/documentation/us/en/software/junos/junos-overview/junos-overview.pdf
Supports
- Routing Engine and Packet Forwarding Engine architecture
- Separation of control operations from packet forwarding
- Routing Engine software processes and active-route selection
- Forwarding-table transfer to the Packet Forwarding Engine
- https://www.juniper.net/documentation/us/en/software/junos/cli/topics/topic-map/junos-cli-operational-overview.html
Supports
- Operational mode for monitoring and troubleshooting
- Purposes of show, ping, traceroute, request, and configure
- CLI Explorer and question mark help
- https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/command/commit.html
Supports
- Commit activation
- Commit check validation without activation
- Confirmed commit timer and automatic rollback
- Commit comments and platform-specific options
- https://www.juniper.net/documentation/us/en/software/junos/cli/topics/topic-map/junos-configuration-managing.html
Supports
- Rollback numbers and loading committed configurations
- Commit required to activate a loaded rollback
- Candidate comparison with active or earlier configurations
- Configuration history and differences
- https://www.juniper.net/documentation/us/en/software/junos/junos-overview/topics/concept/junos-software-routing-forwarding-table-overview.html
Supports
- Routing protocol process and multiple routing tables
- Active-route selection
- Forwarding-table installation and transfer
- Unicast, multicast, and MPLS routing information
- https://www.juniper.net/documentation/us/en/software/junos/static-routing/topics/topic-map/config_junos_routing_table.html
Supports
- Routing table and forwarding table distinction
- IPv4 unicast inet.0 table
- Active routes installed in the forwarding table
- Separate IPv4 and IPv6 routing tables
- https://www.juniper.net/documentation/us/en/software/junos/interfaces-fundamentals/topics/topic-map/protocol-family-interface-address-properties.html
Supports
- Physical interface, logical unit, family, and address hierarchy
- Inet and inet6 family meanings
- IPv4 prefix configuration example
- Platform-specific protocol-family notes
- https://github.com/sindresorhus/awesome
Supports
- Discovery starting point for curated awesome lists
- Networking category and listed software-defined networking collection
- https://github.com/networktocode/awesome-network-automation
Supports
- Curated discovery of network automation tools
- Junos PyEZ, NAPALM, Netmiko, and Ansible ecosystem relevance
- https://www.juniper.net/documentation/product/us/en/junos-pyez/
Supports
- Python microframework for managing and automating Junos devices
- Setup, developer guides, release notes, and support resources
- https://napalm.readthedocs.io/en/latest/
Supports
- Unified API across supported network operating systems
- Junos driver support
- Configuration manipulation and operational data retrieval
- https://ktbyers.github.io/netmiko/PLATFORMS.html
Supports
- Python library simplifying SSH connections to network devices
- Juniper Junos listed as a regularly tested platform
- https://docs.ansible.com/projects/ansible/latest/collections/junipernetworks/junos/index.html
Supports
- Junipernetworks Junos collection availability
- Manual installation direction
- Collection module and plugin documentation