JNCIA-Junos study guide
JNCIA-Junos · Work through your exam, one topic at a time.
The Juniper Networks Certified Associate – Junos (JNCIA-Junos) is an entry-level certification that verifies you can work confidently in the Junos OS command-line interface and understand the fundamentals of IP networking. It is the usual starting point for network engineers, NOC and operations staff, and anyone who administers Juniper routers, switches, or SRX firewalls, and it also serves as the foundation for Juniper's higher-tier specialist tracks. The JNCIA-Junos study guide has 7 sections and about 2,394 words.
01Networking Fundamentals
Junos questions lean on general networking. Know the seven OSI layers and what lives at each: Ethernet frames and MAC addresses at Layer 2, IP addressing, ARP and ICMP at Layer 3, TCP/UDP ports at Layer 4.
316 words, about 2 min02Junos OS Fundamentals
The single most important idea is that Junos OS, built on FreeBSD, separates the control plane from the forwarding plane. The Routing Engine (RE) runs routing protocols, maintains the routing table (RIB) and runs management processes.
324 words, about 2 min03User Interfaces
Operational mode (prompt ends in ) is for monitoring: show, monitor, request, clear, ping, traceroute. Configuration mode (prompt ends in #) is entered with configure and edits the candidate configuration.
348 words, about 2 min04Configuration Basics
Junos configuration is a tree. set, delete and replace: statements edit it.
356 words, about 2 min05Operational Monitoring and Maintenance
Core operational commands: show version, show chassis alarms, show chassis routing-engine, show system uptime, show interfaces terse (one line per interface with admin and link state), show interfaces extensive (errors, drops, queue counters), show arp, show route and show route forwarding-table (the FIB as the PFE sees it), show log messages, show log chassisd. Pipe filters sharpen output: show interfaces match up, except, count, no-more.
343 words, about 2 min06Routing Fundamentals
The Routing Engine computes routes and rpd builds the routing table. For each prefix only the best route is active and installed into the forwarding table used by the PFE.
340 words, about 2 min07Routing Policy and Firewall Filters
Match conditions in from include protocol, prefix-list, route-filter (with exact, longer, orlonger, upto /n, prefix-length-range), community, as-path, neighbor and interface. Actions in then include accept, reject, next term, next policy, metric, preference, local-preference, community add or delete, next-hop and as-path prepend.
367 words, about 2 min