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Copyright 2009Huawei Technologies Co., Ltd. All rights reserved.
VRP Troubleshooting Basics
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 1
Foreword
With the development of technology, network becomes more
and more complicated, and then there will be more probability
to occur faults and also will be more difficult to diagnose it.
As people do works on the network more and more, if the
network faults and can not be fixed in time, it may cause big
lost, even disaster.
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2Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 2
Objectives
Upon completion of this course, you will be able to:
Understand faults classification and common disposal method
Grasp the basic idea of fault diagnose process
Grasp common diagnose tools and commands
Perform basic trouble shooting and device operation and
maintenance
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 3
Contents
1. Fault classification and common disposal method
2. Common diagnose tools and command
3. Basic idea of fault diagnose and examples
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3Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 4
Fault Classification
ConnectionProblem
Performance Problem
FaultClassification
hardwaremediapower
faults
Mis-configuration
Network
congestion
Sub-best route to
destination
Insufficiency
power
Route loops
Network faults
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Fault Common Disposal Methods
Fault Removed
By replace
By segment
By block
By layer
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Idea of By Layer
Physical layer Data Link Layer Network Layer
Connect another device with one physical medium
Send and recieve binary data flow between ends
Interwork with data link layer
Main
Functions
Factors cableconnecting headsignal voltcodeingclockframe structure
Idea of
Trouble
shooting
Only when lower levels work normally, its high level may work normal
Forward information between network layer and physical layer
Define how to access and share for medium and identify device
Define how build frame according to binary data
Inconsistent encapsulation, etc. display interface shows physical interface is up, protocol is down. The fault occurs in the data link layer.
The usage of link, etc. link bandwidth is out of use.it may cause the fault connection or low performance of network
Segment
encapsulation
de-encapsulation the data Send error information Search the best route to send information
Wrong IP address or subnet mask
Overlapping IP address Routing protocol fault
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Idea of By Block
display current-configuration
view configuration
Port partaddress,
encapsulation, cost,
authentication, etc.
Access partsconsoleTelnetdial ,etc
OthersVPN configurationQos configuration, etc
Management partrouter name,
password, service, log, etc.)
Policy partroute policy, policy based route, security configuration,
etc.
Routing partstaticRIPOSPFBGProute
import
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Idea of By Segment
Host to Router LAN
interface
Router to CSU/DSUinterface
CSU/DSUto
telecommparts
interface
WAN Circuit
CSU/DSUor Router itself
Fault removed
Split the big network into several small networks
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Idea of By Replace
By replace is a common method for hardware error trouble
shooting
Doubtable of error LPU or device
Normal LPU or device
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6Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 10
Contents
1. Fault classification and common disposal method
2. Common diagnose tools and command
3. Basic idea of fault diagnose and examples
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 11
Common Diagnose Commands
debugging
View the router/switchs current
status, check the neighbor router,
monitor the network, locate the
network faults.
display
Test the passed nodes of packet
from sender to destination,
most used to locate the faults of
the network
Check the IP reachability of
network or host
ping
Help user to get the detailed
information of the packet
switching and processing.
tracert
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Ping in VRP
ping [ ip ] [ -a source-ip-address | -c count | -d | -f | -h ttl-
value | -i interface-type interface-number | -m time | -n | -p
pattern | -q | -r | -s packetsize | -t timeout | -tos tos-value | -v |
-vpn-instance vpn-instance-name ] * host
ping lsp [ -a source-ip-address | -c count | -exp exp-value | -h
ttl-value | -m time | -r reply-mode | -s packet-size | -t timeout |
-v ] * { ip destination-ip-address mask-length [ ip-address ] | te
tunnel tunnel-id }
Notes: for the difference of VRP version, some of the
parameters can be supported are different.
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 13
Ping in Windows
ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS][-r count]
[-s count] [[-j host-list] | [-k host-list]][-w timeout]
target_name
Target_name can be target hostname or target IP address.
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Tracert in VRP
tracert [ -a source-ip-address | -f first-TTL | -m max-TTL | -p
port | -q nqueries | -vpn-instance vpn-instance-name | -w
timeout ] * host
tracert lsp [ -a source-ip-address | -exp exp-value | -h ttl-
value | -r reply-mode | -t timeout ] * { ip destination-ip-address
mask-length [ ip-address ] | te tunnel tunnel-id }
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Tracert in Windows
tracert [-d] [-h maximum_hops] [-j host-list] [-w timeout]
target_name
Options:
-d Do not resolve addresses to hostnames.
-h maximum_hops Maximum number of hops to search for target.
-j host-list Loose source route along host-list.
-w timeout Wait timeout milliseconds for each reply.
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9Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 16
Display Introduction
Display can be used in all views, easy users to view most of the
information
View the running
status and statistics
information of
interface
View running
configuration
saved
configuration
Version of system software
Type of router or switch
The running time from last start
Information of MPU Information of LPU
display current-configuration/saved-configuration
display version display interface
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 17
Debugging Introduction
Debugging can be used to get the detailed information of
packet switching and processing. Effectively to locate the
network faults.
Using it when
network in low
load or non-
busy time
range
Try to reduce the
affect range of
debugging
Debugging all is
not suggested
unless necessary
When get the
necessary
information, close
the debugging
immediately
Reduce the usage
of system resource
Before using it,
you should full
grasp the usage
of the
debugging
command
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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 18
Display Together with Debugging
...
Provide the now running status of devicestatic
First using display to get the running information of device,
analyze the likely reason and then reduce the check range of
fault.
...
Provide the running information in a time rangedynamic
Debugging the required command, view the debugging
information, diagnose it and remove the faults.
display
debugging
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 19
Contents
1. Fault classification and common disposal method
2. Common diagnose tools and command
3. Basic idea of fault diagnose and examples
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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 20
Basic Steps of Fault Disposal
Fault occurs
Solve the fault
View fault phenomenon
Collect fault information
Judge and analyze
List possible reasons
Trouble-shooting
Back to the former
network stateRecord the documents
End
YesNo
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 21
Analysis of Trouble Shooting
Network
Ethernet
PC4130.1.1.2/16
RouterA
RouterB
RouterC
Ethernet
Server2120.1.1.2/16
Server1110.1.1.8/16
PC3110.1.1.9/16
A schoolyard network, including three network segments. 110.1.0.0/16 s user network segment, 110.1.1.8 is log server. 120.1.0.0/16 is network server segment
One dayuser found that log server1 can not back up the logs of server2
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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 22
View the Fault Phenomenon
log server1 can not back up the logs of server2 is not a complete, clear
fault description. Network maintainer should guide the user to answer such
questions
Is the fault continuous? Or some times
Is it the connection problem (ping to check), or performance problem (back up
speed is low)
which network segment or server have the affection, what is the IP address?
After contacted with user, got the problem description:
At the peak of network load, the transfer of FTP from log server 110.1.1.8 to
server 2120.1.1.2 is about 0.6Mbit/s, too slow.
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 23
Collect Fault Information
Ask users questions about the network fault or key users
Methods of FaultInformation Collection
Prepare RelatedQuestions
Result
Network topology or configuration changed recently?
Users belong to network segment 110.1.0.0 increase fast
According to users fault, using tools to collect information, like network management system, protocol analyzer, display /debugging command etc.
Whether any users access affected servers successfully
PC4 in 130.1.0.0/16 FTP backup server with normal speed 7Mbit/s, but FTP log server slowly, only with speed 6Mbit/s
Compare the test performance and network standard
In the non-peak time, whats the bandwidth of FTP between log server and backup server?
In the non-peak time, the bandwidth of FTP between log server and backup server is 6Mbit/s
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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 24
Judge and Analyze
Ensure the fault range by using the former information and
trouble-shooting experience and the mastering knowledge of
Internet devices and protocols. By dividing fault range, ensure
the caring fault or devicesmedium and hosts.
In this case, now we can ensue that the problem is descending
network performance. Then, which one ? Is it 110.1.0.0Is it
inter-network including RouterARouterBRouterCOr is it
120.1.0.0
Because the FTP speed between hosts in 130.1.0.0 and backup
server is normal, there is no fault in 120.1.0.0.
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 25
List Probable Reasons
After Judging by experience and analyzing by theory, we can
summarize all the probable reasons.
The probable reasons are
1110.1.0.0 performance problem, the probable reasons are:
Log server Server1 performance problem
the gateway of 110.1.0.0 performance problem
110.1.0.0 itself performance problem
2 inter-network performance problem, the probable reasons are:
The route to segment 120.1.0.0 is not the best route.
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Trouble-shooting for Every Reason
According to all the listing reasons, make a plan for trouble-
shooting, and analyze the most probable reason.
Attentionoperation only one variable one time.
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 27
Circulation Fault Trouble-shooting 1
When one trouble-shooting way can not get the expectant aims, go into this step.
Before going into next circulation, the network must be in the former state before the
former trouble-shooting way. If not, it may cause new network problems.
Ensure one new trouble-shooting way according to new next reason and do it.
When one trouble-
shooting way can not
get the expectant aims,
go into this step.
Circulation fault trouble-shooting point
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Circulation Fault Trouble-shooting 2
Probable reason 1Its not the best route from 110.1.0.0 to
20.1.0.0
...
Probable reason 2
Log server Server1 performance problem
Probable reason 3
The problem of the gateway of 110.1.0.0
Probable reason 4
110.1.0.0 itself performance problem
scheme
in 110.1.0.0 network segment tracert10.15.245.253
the time for reply packets coming back is only 10ms. Its not this reason. Go into circulation fault trouble-shooting
scheme
check FTP speed between PC3 in the same network segment and Server1. And its normal 6Mbit/s. Its not this reason.
scheme
use display command to check the statistic information of receiving and sending information on the switch in the110.1.0.0 network. In the output packets, unicast packets are 3 times as broadcast. Its abnormally big.
use display command to check the statistic information of receiving and sending information on the switch in the120.1.0.0 network. In the output packets, unicast packets are 300 times as broadcast. Its normal.
scheme
check FTP speed between PC3 and backup Server2. And its normal 7Mbit/s. Its not this reason.
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 29
Circulation Fault Trouble-shooting 3
Communicate customers againand ensure the service in this network
segmentand get the true fault reason110.1.0.0 is ordinary users
network segment. Because of serviceevery user needs to send lots of
broadcast and multicast packets. When more and more users access
this networkthe server in this network will cost more resource to
deal with such packets. So, the transmission of service will low.
Fault reason solutionthis is the performance problem because of
incorrect network deploy. Relocate the serverit means to remove the
server in 120.1.0.0 network segment. Fault solved.
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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 30
View the Fault Trouble-shooting Result
After implementing one trouble-shooting way according to one
reason, we need to analyze the result and judge whether the
problem is solved or not, and whether new problem is
generated.
If problem is solved, we can record the documents ; If not, it
need to trouble-shooting again.
Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 31
Record the Trouble-shooting Documents
Documentsrecord
Fault phenomenondescription and
Information collection
Experience
Topology
Device listmediumprotocol and application list
Trouble-shooting ways
and results
Reasons
Documents are the summary of experience
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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page 32
Summary
What are the major ways to deal with IP network fault
What are the major processes to deal with IP network fault
What are the commonly used commands for dealing with fault
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