JN0-690 Junos Troubleshooting

Junos Troubleshooting Exam Objectives (Exam: JN0-691)

Troubleshooting Methodology
Identify the elements to build a framework for approaching troubleshooting Junos devices
General troubleshooting methodology
Broad troubleshooting steps
Identify tools that can be used to troubleshoot Junos devices
CLI
Craft interface
Logging
Traceoptions
Real-time monitoring
Core files
Port mirroring
Identify tools that can be used for device and network monitoring
SNMP
RMON
Sampling

Chassis Monitoring and Troubleshooting
Identify the concepts, tools and features used to monitor and troubleshoot chassis-related components of Junos devices
Chassis
RE and PFE components
Fans and power supplies
System
Storage and file system
Boot media and start-up sequence
System software
Backups
Given a scenario, demonstrate knowledge of how to monitor and troubleshoot the chassis and core system components of Junos devices
show commands
Logging

Control Plane Monitoring and Troubleshooting
Identify the concepts, tools and features used to monitor and troubleshoot the control plane of Junos devices
System processes
User processes
ARP
RIB/FIB
Given a scenario, demonstrate knowledge of how to monitor and troubleshoot the control plane of Junos devices
show commands
clear commands
monitor commands
Logging
Traceoptions

Data Plane Monitoring and Troubleshooting
Identify the concepts, tools and features used to monitor and troubleshoot the data plane of Junos devices
PFE issues
Ethernet interfaces
MTU issues
Link flapping
Forwarding table issues
PFE load balancing
Local vs. transit traffic
Firewall filters and policers
Given a scenario, demonstrate knowledge of how to monitor and troubleshoot the data plane of Junos devices
request commands
show commands
monitor commands
clear commands
Loopback testing

Layer 2 and Layer 3 Protocol Monitoring and Troubleshooting
Identify the concepts, tools and features used to monitor and troubleshoot Layer 3 protocols on Junos devices
Routing table information
Routing loops
OSPF neighbors
OSPF adjacencies
BGP peering and peer groups
BGP neighbor states
Identify the concepts, tools and features used to monitor and troubleshoot Layer 2 protocols on Junos devices
VLAN’s
bridging concepts
xSTP protocols
switching table
Given a scenario, demonstrate knowledge of how to perform basic monitoring and troubleshooting of Layer 3 protocols on Junos devices
show commands
clear commands
Traceoptions
Given a scenario, demonstrate knowledge of how to perform basic monitoring and troubleshooting of Layer 2 protocols on Junos devices
show commands
clear commands
Traceoptions

High Availability (HA) Monitoring and Troubleshooting
Identify the concepts, tools and features used to monitor and troubleshoot HA components for Junos devices
Graceful Routing Engine switchover (GRES)
Graceful restart (GR)
Nonstop active routing/bridging
Virtual router redundancy protocol (VRRP)
Link aggregation groups (LAG)
Unified in-service software upgrade (ISSU)
Given a scenario, demonstrate knowledge of how to perform monitoring and troubleshooting of HA features on Junos devices
monitor commands
show commands
request commands

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QUESTION 1
Which CLI command is used to restart a software process?

A. restart
B. reboot
C. commit
D. reload

Answer: A

Explanation: To restart a process one have to use restart <process name>, reboot is not even a
valid command.
Possible completions:
restart Restart software process

---

QUESTION 2
Which CLI command applies the candidate configuration to the active configuration?

A. load
B. merge
C. copy run start
D. commit

Answer: D

Explanation: Copy run start is a Cisco specific command and is nowhere to be found in Junos.
>commit Commit current set of changes

---

QUESTION 3
Which operational CLI command would you use to troubleshoot hardware-related problems?

A. show system
B. show chassis
C. show route
D. show cli

Answer: B

Explanation: Show route will only show you routing, show chassis will show you hardware related
information.
>show chassis ?
Possible completions:
alarms Show alarm status
cluster Show chassis cluster information
craft-interface Show craft interface status
environment Show component status and temperature, cooling system speeds
fan Show fan and fan tray information
firmware Show firmware and operating system version for components
forwarding Show forwarding process (fwdd) status
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
temperature-thresholds Show chassis temperature threshold settings
usb Show chassis USB status

---

QUESTION 4
In the Junos OS, which type of file dumps the program’s environment in the form of memory
pointers, instructions, and register data to a file in the event of a panic or other serious
malfunction?

A. log file
B. backup file
C. configuration file
D. core file

Answer: D

Explanation: Junos will under a panic create a core-dump file, definitely not a backup file.
> show system core-dumps
/var/crash/*core*: No such file or directory
/var/tmp/*core*: No such file or directory
/var/tmp/pics/*core*: No such file or directory
/var/crash/kernel.*: No such file or directory
/tftpboot/corefiles/*core*: No such file or directory

---

QUESTION 5
Which operational CLI command would you use to display information about the system and
software processes?

A. show system
B. show chassis
C. show route
D. show cli

Answer: A

Explanation: Show route will only show you routing, show system will show you software related
information:
>show system ?
Possible completions:
alarms Show system alarm status
audit Show file system MD5 hash and permissions
auto-snapshot Show auto-snapshot status when system booted from alternate slice
autoinstallation Show autoinstallation information
autorecovery Show autorecovery information
boot-messages Show boot time messages
buffers Show buffer statistics
certificate Show installed X509 certificates
commit Show pending commit requests (if any) and commit history
configuration Show configuration information
connections Show system connection activity
core-dumps Show system core files
directory-usage Show local directory information
download Show status of downloads
firmware Show all firmware version information
health Show online diagnostic status
license Show feature licenses information
login Show system login state
memory Show system memory usage
processes Show system process table
queues Show queue statistics
reboot Show any pending halt or reboot requests
resource-cleanup Show resource cleanup information
rollback Show rolled back configuration
services Show service applications information
snapshot Show snapshot information
software Show loaded JUNOS extensions
statistics Show statistics for protocol
storage Show local storage data
threads Show system threads table
uptime Show time since system and processes started
users Show users who are currently logged in
virtual-memory Show kernel dynamic memory usage

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