3troubleshootingjunos

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Network Utiliti s and A lications: Part 2

JUNOS Software off rs support for Telnet, SSH or SCP, and FTP. As with the ping and

traceroute utiliti s, th se applications support switches that are useful in

troubleshooting. The following are some of the key switches:

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no-resolve: This switch disables the normal reverse lookup

performed the host address specified in a telnet command. Use

this switch when sessions take a long time to open because of the

inability to perform the reverse lookup.

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port: The port switch allows you to specify a destination port other than

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the default port normally associated with that service.

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routing-instance: This switch supports VPN and routing instance

context for applications like Telnet and FTP. A classic use would be to

establish a Telnet connection from a provider edge (PE) router to an

attached customer edge (CE) device, which, being part of a VPN, would

reside in a specific routing table and instance.

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source: As with ping, altering the source address used in a connection

request might uncover problems with routing that prevent connection

establishment when sourcing traffic from the egress interface (the

default).

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Network Utilities and A lications: Part 3

The monitor traffic command provides CLI-based access to the tcpdump utility.

This command monitors only traffic originating or terminating local the RE. This

capability is the best way to monitor and diagnose problems at Layer 2 with JUNOS

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Softwa e because tracing, which is similar to debug on equipment from other

vendo s, does not function for Layer 2 protocols. We cover tracing subsequent

pages that deal with system logging.

N te that p t col filtering functions (for example, matching on only UDP traffic sent

m a specific port) are currently not supported for real-time monitoring because in

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real-time m de, the Layer 2 headers are stripped at ingress, which prevents filtering

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Troubleshooting Tools: Th Craft Interface Panel

The slide highlights the topic we discuss next.

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The Craft Interface

The craft interface pan l for syst

ms that support the LCD status screen is an

excellent troubleshooting and op

rational analysis tool because it provides

component and system alarm status in a manner that is easy to interpret. When

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wo king emotely you can issue a show chassis craft-interface command

to obtain an ASCII representation of the LEDs and messages that the craft interface

displays.

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Troubleshooting Tools: Syst m Logs and Protocol Tracing

The slide highlights the topic we discuss next.

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Troubleshooting JUNOS Platforms

Syslog Options Example (contd.)

The following table illustrates the mapping of numeric codes to message severity:

0

emergency

System panic or other condition that causes the

routing platform to stop functioning

1

alert

Conditions that require immediate correction, such as a

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corrupted system database

2

critical

Critical conditions, such as hard disk err rs

3

error

Error conditions that generally have less ser us

consequences than errors in the emergency, alert, and critical

levels

4

warning

Conditions that warrant monitoring

5

notice

Conditions that are no

errors b t might warrant

special handling

6

info

Events or nonerror con

itions of interest

7

debug

Software debugging messages; specify this level only when so

directed by a technical support representative

The following are examples f a sysl g message, both with and without an explicit

priority, respectively:

Aug 21 12:36:30 router1 chassisd[522]: %DAEMON-6 CHASSISD PARSE COMPLETE:

Aug 21 12:36:30 router1 chassisd[522]: CHASSISD PARSE COMPLETE: Using new

configuration

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