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JNCIE-SP: System and Platform Configuration

JNCIE-SP · Work through your exam, one topic at a time.

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System and Platform Configuration

What this domain tests

This domain checks operational fluency with Junos OS itself: local and remote authentication, login classes, syslog destinations, NTP synchronization, SNMP access, chassis/interface configuration, and the software upgrade and commit lifecycle. The exam favors exact hierarchy names and predictable rollback behavior.

Core rules and concepts

  • Login classes combine permissions (for example configure, view, interface) with allow-commands and deny-commands regular expressions. A class with configure permission can still be constrained by command regexes.
  • Authentication order is set with set system authentication-order [radius password]; if the first method is unreachable, Junos falls through to the next.
  • Syslog uses facility and severity: set system syslog file messages any info. Severities run emerg, alert, crit, err, warning, notice, info, debug. Add archive size 10m files 10 world-readable for rotation.
  • NTP needs a server, optionally prefer, and for authentication a key, trusted-key, and the same key attached to the server.
  • SNMP v2c uses a community with authorization read-only; v3 uses USM users with authentication and privacy.
  • Software is added with request system software add <package> validate reboot; rollback returns to the previous set, snapshot copies to the alternate root, and zeroize wipes configuration.

Worked example

A router must authenticate to an NTP server using MD5 key 1:

set system ntp authentication-key 1 type md5 value JunosNTP!
set system ntp trusted-key 1
set system ntp server 192.0.2.10 key 1 prefer

Reasoning: the first line defines key material; trusted-key 1 tells ntpd to trust key ID 1; key 1 on the server attaches that key to the association. Without trusted-key, authenticated packets are rejected. prefer makes this server the primary source.

Traps

  • commit check validates syntax but does not apply; commit confirmed 5 auto-rolls back unless confirmed with a second commit.
  • A syslog severity logs that severity and all more severe messages, not just that level.
  • request system software add requires a package matching the RE platform; no-validate skips checks and is risky.
  • A login class without allow-commands is not automatically limited; permissions and command regexes are separate controls.