4. oda021003 vrp troubleshooting basics issue1

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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.

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


Contents

1. Fault classification and common disposal method

2. Common diagnose tools and command

3. Basic idea of fault diagnose and examples


Fault Classification

ConnectionProblem

Performance Problem

FaultClassification

hardwaremediapower

faults

Mis-configuration

Network

congestion

Sub-best route to

destination

Insufficiency

power

Route loops

Network faults


Fault Common Disposal Methods

Fault Removed

By replace

By segment

By block

By layer


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


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


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


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


Contents





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


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.


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.


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 }


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.


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


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

10


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


Contents




11


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


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

12


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.


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

13


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.


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.

14


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.


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

15



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.



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.

16


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.


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

17


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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