Chapter 1 System Maintaining and Debugging
When maintaining and debugging the system, go
to these sections for information you are interested in:
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System
Maintaining and Debugging Overview
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System
Maintaining and Debugging
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System
Maintaining Example
1.1 System Maintaining and Debugging Overview
1.1.1 Introduction to System Maintaining and Debugging
You can use the ping command and the
tracert command to verify the current network connectivity.
I. The ping command
You can use the ping command to
verify whether a device with a specified address is reachable, and to examine
network connectivity.
The ping command involves the following
steps in its execution:
1)
The source device sends an ICMP echo request to
the destination device.
2)
If the network is functioning properly, the
destination device responds by sending an ICMP echo reply to the source device after
receiving the ICMP echo request.
3)
If there is network failure, the source device
displays timeout or destination unreachable.
4)
Display related statistics.
Output of the ping command includes:
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Information on the destination’s responses
towards each ICMP echo request, if the source device has received the ICMP echo
reply within the timeout time, it displays the number of bytes of the echo
reply, the message sequence number, Time to Live (TTL), and the response time.
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If within the period set by the timeout timer,
the destination device has not received the ICMP response, it displays the prompt
information.
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The ping command can apply to the destination’s
name or IP address. If the destination’s name is unknown, the prompt information
is displayed.
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The statistics during the ping operation, which
include number of packets sent, number of echo reply messages received,
percentage of messages not received, the minimum, average, and maximum response
time.
II. The tracert command
By using the tracert command, you
can trace the switches involved in delivering a packet from source to
destination. This is useful for identification of failed node(s) in the event
of network failure.
The tracert command involves the
following steps in its execution:
1)
The source device sends a packet with a TTL
value of 1 to the destination device.
2)
The first hop (the routing device that first receives
the packet; the value of TTL decreases by 1 by each hop) responds by sending a
TTL-expired ICMP message to the source, with its IP address encapsulated. In
this way, the source device can get the address of the first switch.
3)
The source device sends a packet with a TTL
value of 2 to the destination device.
4)
The second hop responds with a TTL-expired ICMP message,
which gives the source device the address of the second routing device.
5)
The above process continues until the ultimate
destination device is reached. In this way, the source device can trace the
addresses of all the routing devices that a packet traverses from the source
device to the destination device.
The device provides various debugging
functions. For the majority of protocols and features supported, the system
provides corresponding debugging functions to help users diagnose errors.
The following two switches control the display
of debugging information:
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Protocol debugging switch, which controls the
output of protocol-specific debugging information
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Screen output switch, which controls whether to display
the debugging information on a certain screen.
Figure 1-1 illustrates
the relationship between the protocol debugging switch and the screen output
switch. Only when both are turned on can debugging information be output on a
terminal.
Figure 1-1 The relationship between the protocol and screen debugging switch
1.2 System Maintaining and Debugging
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To do…
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Use the command…
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Remarks
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Check whether a specified IP address can
be reached
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ping [ ip
] [ -a source-ip | -c count | -f | -h
ttl | -i interface-type interface-number | -m interval
| -n | -p pad | -q | -r | -s packet-size
| -t timeout | -tos tos | -v | -vpn-instance
vpn-instance-name ] * remote-system
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Optional
Used in IPv4 network
Available in any view
|
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ping [ ipv6
] [ -a source-ip | -c count | -m interval
| -s packet-size | -t timeout ] * remote-system
[ -i interface-type interface-number ]
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Optional
Used in IPv6 network
Available in any view
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View the routes from the source to the
destination
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tracert [ -a
source-ip | -f first-ttl | -m max-ttl |
-p port | -q packet-number | -vpn-instance vpn-instance-name
| -w timeout ] * remote-system
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Optional
Used in IPv4 network
Available in any view
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|
tracert [ ipv6
] [-f first-ttl | -m max-ttl | -p port
| -q packet-number | -w timeout ] * remote-system
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Optional
Used in IPv6 network
Available in any view
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For a low-speed network, you are recommended to set
a larger value for the timeout timer (indicated by the -t parameter in
the command) when configuring the ping command.
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Only the directly connected segment address can
be pinged if the outgoing interface is specified with the -i argument.
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To do…
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Use the command…
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Remarks
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Enable debugging for a specified module
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debugging
{ all [ timeout time ] | module-name [ option ]
}
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Required
Disabled by default
Available in user view
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Enable the terminal monitoring
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terminal monitor
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Optional
The terminal monitoring on the console is
enabled by default and that on the monitoring terminal is disabled by
default.
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Enable the terminal debugging
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terminal debugging
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Required
Disabled by default
Available in user view
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Display the enabled debugging functions
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display debugging
[ interface interface-type interface-number ] [
module-name ]
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Optional
Available in any view
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Display information about the optical
modules connected to the optical interfaces on the switch
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display lpu fiber-module [ interface-type interface-number ]
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Optional
Available in any view
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The debugging commands are usually used by
administrators in diagnosing network failure.
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Output of the debugging information may reduce
system efficiency, especially during execution of the debugging all
command.
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After completing the debugging, you are
recommended to use the undo debugging all command to disable all the
debugging functions.
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You must configure the debugging, terminal
debugging and terminal monitor commands first to display the detailed
debugging information on the terminal. For the detailed description on the terminal
debugging and terminal monitor commands, refer to Information
Center Commands in the System Volume.
1.3 System Maintaining Example
I. Network requirements
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The IP address of the destination device is
10.1.1.4.
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Display the routing devices a packet traverses from
the current device to the destination device.
II. Network diagram (omitted here)
III. Configuration procedure
<Sysname> tracert nis.nsf.net
traceroute to nis.nsf.net (10.1.1.4)
30 hops max, 40 bytes packet
1 128.3.112.1 19 ms 19 ms 10 ms
2 128.32.216.1 39 ms 39 ms 19 ms
3 128.32.136.23 39 ms 40 ms 39 ms
4 128.32.168.22 39 ms 39 ms 39 ms
5 128.32.197.4 40 ms 59 ms 59 ms
6 131.119.2.5 59 ms 59 ms 59 ms
7 129.140.70.13 99 ms 99 ms 80 ms
8 129.140.71.6 139 ms 239 ms 319
ms
9 129.140.81.7 220 ms 199 ms 199
ms
10 10.1.1.4 239 ms 239 ms 239 ms
The above output shows that a packet
traverses nine routing devices from the source to the destination device.
