Huawei V200R001C01 Operating instructions

Huawei AR2200-S Series Enterprise Routers
V200R001C01
Troubleshooting
Issue 01
Date 2012-01-06
HUAWEI TECHNOLOGIES CO., LTD.

Copyright © Huawei Technologies Co., Ltd. 2012. All rights reserved.
No part of this document may be reproduced or transmitted in any form or by any means without prior written
consent of Huawei Technologies Co., Ltd.
Trademarks and Permissions
and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.
All other trademarks and trade names mentioned in this document are the property of their respective holders.
Notice
The purchased products, services and features are stipulated by the contract made between Huawei and the
customer. All or part of the products, services and features described in this document may not be within the
purchase scope or the usage scope. Unless otherwise specified in the contract, all statements, information,
and recommendations in this document are provided "AS IS" without warranties, guarantees or representations
of any kind, either express or implied.
The information in this document is subject to change without notice. Every effort has been made in the
preparation of this document to ensure accuracy of the contents, but all statements, information, and
recommendations in this document do not constitute the warranty of any kind, express or implied.
Huawei Technologies Co., Ltd.
Address: Huawei Industrial Base
Bantian, Longgang
Shenzhen 518129
People's Republic of China
Website: http://www.huawei.com
Email: [email protected]
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About This Document
Intended Audience
This document describes the procedure for troubleshooting various services supported by the
AR2200-S in terms of common causes, flowchart, troubleshooting procedure, alarms and logs,
and case studies.
This document is intended for:
lSystem maintenance engineers
lCommissioning engineers
lNetwork monitoring engineers
Symbol Conventions
The symbols that may be found in this document are defined as follows.
Symbol Description
DANGER
Indicates a hazard with a high level of risk, which if not
avoided, will result in death or serious injury.
WARNING
Indicates a hazard with a medium or low level of risk, which
if not avoided, could result in minor or moderate injury.
CAUTION
Indicates a potentially hazardous situation, which if not
avoided, could result in equipment damage, data loss,
performance degradation, or unexpected results.
TIP
Indicates a tip that may help you solve a problem or save
time.
NOTE
Provides additional information to emphasize or supplement
important points of the main text.
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Command Conventions
The command conventions that may be found in this document are defined as follows.
Convention Description
Boldface The keywords of a command line are in boldface.
Italic Command arguments are in italics.
[ ] Items (keywords or arguments) in brackets [ ] are optional.
{ x | y | ... } Optional items are grouped in braces and separated by
vertical bars. One item is selected.
[ x | y | ... ] Optional items are grouped in brackets and separated by
vertical bars. One item is selected or no item is selected.
{ x | y | ... }*Optional items are grouped in braces and separated by
vertical bars. A minimum of one item or a maximum of all
items can be selected.
[ x | y | ... ]*Optional items are grouped in brackets and separated by
vertical bars. Several items or no item can be selected.
&<1-n> The parameter before the & sign can be repeated 1 to n times.
# A line starting with the # sign is comments.
Change History
Updates between document issues are cumulative. Therefore, the latest document issue contains
all updates made in previous issues.
Changes in Issue 01 (2010-01-06)
Initial commercial release.
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Contents
About This Document.....................................................................................................................ii
1 Hardware.........................................................................................................................................1
1.1 Board Registration Troubleshooting..................................................................................................................2
1.1.1 A Board Fails to Be Registered.................................................................................................................2
2 System..............................................................................................................................................5
2.1 CPU Troubleshooting.........................................................................................................................................6
2.1.1 CPU Usage Is High....................................................................................................................................6
2.2 Telnet Troubleshooting.....................................................................................................................................10
2.2.1 The User Fails to Log in to the Server Through Telnet...........................................................................10
2.3 SSH Troubleshooting.......................................................................................................................................13
2.3.1 The User Fails to Log in to the Server Through SSH.............................................................................13
2.4 Mirroring Troubleshooting...............................................................................................................................17
2.4.1 Monitoring Device Does Not Receive Any Mirrored Packet After Port Mirroring Is Configured.........17
2.4.2 Monitoring Device Does Not Receive Any Mirrored Packets After Traffic Mirroring Is Configured
..........................................................................................................................................................................20
2.4.3 Troubleshooting Cases............................................................................................................................23
2.5 SNMP Troubleshooting....................................................................................................................................26
2.5.1 An SNMP Connection Cannot Be Established........................................................................................26
2.5.2 The NMS Fails to Receive Trap Messages from the Host......................................................................29
2.6 NQA Troubleshooting......................................................................................................................................31
2.6.1 A UDP Jitter Test Instance Fails to Be Started.......................................................................................31
2.6.2 A Drop Record Exists in the UDP Jitter Test Result...............................................................................33
2.6.3 A Busy Record Exists in the UDP Jitter Test Result...............................................................................35
2.6.4 A Timeout Record Exists in the UDP Jitter Test Result.........................................................................37
2.6.5 The UDP Jitter Test Result Is "Failed", "No Result" or "Packet Loss"...................................................39
2.7 NTP Troubleshooting.......................................................................................................................................41
2.7.1 The Clock Is Not Synchronized...............................................................................................................41
2.8 CWMP Troubleshooting...................................................................................................................................42
2.8.1 Failed to Manage AR2200-S Using CWMP...........................................................................................42
3 Physical Connection and Interfaces.........................................................................................46
3.1 Eth-Trunk Interface Troubleshooting...............................................................................................................47
3.1.1 Eth-Trunk Interface Cannot Forward Traffic..........................................................................................47
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3.1.2 Troubleshooting Cases............................................................................................................................51
4 LAN................................................................................................................................................56
4.1 VLAN Troubleshooting....................................................................................................................................57
4.1.1 Users in a VLAN Cannot Communicate with Each Other......................................................................57
4.2 MAC Address Table Troubleshooting.............................................................................................................61
4.2.1 Correct MAC Address Entries Cannot Be Generated.............................................................................61
4.3 MSTP Troubleshooting....................................................................................................................................66
4.3.1 MSTP Topology Change Leads to Service Interruption.........................................................................66
4.4 Transparent Bridging Troubleshooting............................................................................................................72
4.4.1 Layer 2 Traffic Forwarding in a Bridge Group Fails..............................................................................72
4.4.2 Traffic Forwarding in IP Routing of Bridge Groups Fails......................................................................75
5 WAN...............................................................................................................................................80
5.1 E1/T1 Troubleshooting.....................................................................................................................................81
5.1.1 E1/T1 Interface in Up State Fails to Correctly Send and Receive Data..................................................81
5.2 FR Troubleshooting..........................................................................................................................................85
5.2.1 Local Device Fails to Ping the Remote Device When the Link Protocol Status of Their Connected FR
Interfaces Is Up.................................................................................................................................................85
5.2.2 Troubleshooting Cases............................................................................................................................92
5.3 MFR Troubleshooting......................................................................................................................................92
5.3.1 Local Device Fails to Ping the Remote Device When the Link Protocol Status of Their Connected MFR
Interfaces Is Up.................................................................................................................................................93
5.3.2 Troubleshooting Cases............................................................................................................................98
5.4 DCC Troubleshooting.......................................................................................................................................99
5.4.1 Failed to Initiate Calls..............................................................................................................................99
5.4.2 Failed to Receive Calls..........................................................................................................................103
5.5 ISDN Troubleshooting...................................................................................................................................107
5.5.1 Link Failed to Be Established on ISDN Interfaces................................................................................107
5.6 PPPoE Troubleshooting..................................................................................................................................113
5.6.1 PPPoE Dialup Fails...............................................................................................................................113
5.7 PPP Troubleshooting......................................................................................................................................117
5.7.1 Protocol Status of a PPP Interface Is Down..........................................................................................117
5.8 xDSL Troubleshooting...................................................................................................................................122
5.8.1 Packets Fail to Be Forwarded on an ADSL Interface Working in ATM Mode....................................123
5.8.2 Packets Fail to Be Forwarded on a G.SHDSL Interface Working in ATM Mode................................127
5.9 3G Troubleshooting........................................................................................................................................132
5.9.1 3G Calls Failed After Dialing Parameters Were Correctly Set.............................................................132
6 Voice.............................................................................................................................................138
6.1 Voice Service Troubleshooting......................................................................................................................139
6.1.1 No Feed Is Detected on a Telephone.....................................................................................................139
6.1.2 No Dial Tone Is Heard After Offhook...................................................................................................141
6.1.3 Call Quality Is Low...............................................................................................................................143
6.1.4 Busy Tone Is Heard After Offhook.......................................................................................................145
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6.1.5 A Call Fails to Be Connected................................................................................................................149
6.1.6 Calling Number Is Not Displayed on the Called Party's Telephone.....................................................152
6.1.7 Fax Service Fails...................................................................................................................................155
6.1.8 A SIP AG Cannot Work Properly.........................................................................................................158
7 IP Forwarding and Routing.....................................................................................................162
7.1 A Ping Operation Fails...................................................................................................................................163
7.1.1 The Ping Operation Fails.......................................................................................................................163
7.1.2 Troubleshooting Cases..........................................................................................................................171
7.2 DHCP Troubleshooting..................................................................................................................................173
7.2.1 A Client Cannot Obtain an IP Address (the AR2200-S Functions as the DHCP Server).....................173
7.2.2 A Client Cannot Obtain an IP Address (the AR2200-S Functions as the DHCP Relay Agent)...........178
7.3 RIP Troubleshooting.......................................................................................................................................181
7.3.1 Device Does not Receive Partial or All the Routes...............................................................................182
7.3.2 Device Does not Send Some or All Routes...........................................................................................185
7.4 OSPF Troubleshooting...................................................................................................................................189
7.4.1 The OSPF Neighbor Relationship Is Down..........................................................................................189
7.4.2 The OSPF Neighbor Relationship Cannot Reach the Full State...........................................................194
7.4.3 Trouble Cases........................................................................................................................................198
8 Multicast......................................................................................................................................205
8.1 Layer 3 Multicast Troubleshooting................................................................................................................206
8.1.1 Multicast Traffic Is Interrupted.............................................................................................................206
8.1.2 The PIM Neighbor Relationship Remains Down..................................................................................209
8.1.3 The RPT on a PIM-SM Network Fails to Forward Data.......................................................................212
8.1.4 The SPT on a PIM-SM Network Fails to Forward Data.......................................................................216
8.1.5 MSDP Peers Cannot Generate Correct (S, G) Entries...........................................................................221
8.1.6 The Multicast Device Cannot Generate IGMP Entries or MLD Entries...............................................226
9 QoS...............................................................................................................................................231
9.1 Traffic Policy Troubleshooting......................................................................................................................232
9.1.1 Traffic Policy Fails to Take Effect........................................................................................................232
9.1.2 Troubleshooting Cases..........................................................................................................................235
9.2 Priority Mapping Troubleshooting.................................................................................................................237
9.2.1 Packets Enter Incorrect Queues.............................................................................................................237
9.2.2 Priority Mapping Results Are Incorrect................................................................................................240
9.2.3 Troubleshooting Cases..........................................................................................................................244
9.3 Traffic Policing Troubleshooting...................................................................................................................247
9.3.1 Traffic Policing Based on Traffic Classifiers Fails to Take Effect.......................................................247
9.3.2 Interface-based Traffic Policing Results Are Incorrect.........................................................................248
9.3.3 Troubleshooting Cases..........................................................................................................................251
9.4 Traffic Shaping Troubleshooting....................................................................................................................252
9.4.1 Queue-based Traffic Shaping Results Are Incorrect.............................................................................252
9.4.2 Troubleshooting Cases..........................................................................................................................255
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9.5 Congestion Avoidance Troubleshooting........................................................................................................257
9.5.1 Congestion Avoidance Fails to Take Effect..........................................................................................257
9.6 Congestion Management Troubleshooting.....................................................................................................260
9.6.1 Congestion Management Fails to Take Effect......................................................................................260
9.6.2 Troubleshooting Cases..........................................................................................................................263
10 Security......................................................................................................................................266
10.1 AAA Troubleshooting..................................................................................................................................267
10.1.1 RADIUS Authentication Fails.............................................................................................................267
10.1.2 HWTACACS Authentication Fails.....................................................................................................272
10.1.3 Troubleshooting Cases........................................................................................................................278
10.2 ARP Security Troubleshooting.....................................................................................................................284
10.2.1 The ARP Entry of an Authorized User Is Maliciously Modified........................................................284
10.2.2 The Gateway Address Is Maliciously Changed..................................................................................287
10.2.3 User Traffic Is Interrupted by a Large Number of Bogus ARP Packets.............................................289
10.2.4 IP Address Scanning Occurs...............................................................................................................291
10.2.5 ARP Learning Fails.............................................................................................................................294
10.3 NAC Troubleshooting..................................................................................................................................297
10.3.1 802.1x Authentication of a User Fails.................................................................................................297
10.3.2 MAC Address Authentication of a User Fails.....................................................................................301
10.3.3 MAC Address Bypass Authentication of a User Fails........................................................................305
10.4 Firewall Troubleshooting.............................................................................................................................305
10.4.1 SYN Flood Attacks Are Detected on a Network.................................................................................305
10.5 ACL Troubleshooting...................................................................................................................................307
10.5.1 Packet Filtering Firewall Fails Because of Invalid ACL Configuration.............................................307
10.6 NAT Troubleshooting...................................................................................................................................309
10.6.1 Internal Users Fail to Access the Public Network...............................................................................309
10.6.2 External Hosts Fail to Access Internal Servers...................................................................................312
10.6.3 Internal Host with a Conflicting IP Address Fails to Access an External Server................................315
11 Reliability..................................................................................................................................320
11.1 Interface Backup Troubleshooting...............................................................................................................321
11.1.1 Interface Backup Fails to Take Effect.................................................................................................321
11.1.2 Troubleshooting Cases........................................................................................................................324
11.2 BFD Troubleshooting...................................................................................................................................326
11.2.1 BFD Session Cannot Go Up................................................................................................................326
11.2.2 Interface Forwarding Is Interrupted After a BFD Session Detects a Fault and Goes Down...............329
11.2.3 Changed BFD Session Parameters Do Not Take Effect......................................................................331
11.2.4 Dynamic BFD Session Fails to Be Created.........................................................................................333
11.3 VRRP Troubleshooting................................................................................................................................335
11.3.1 Troubleshooting Cases........................................................................................................................335
12 VPN............................................................................................................................................340
12.1 GRE Troubleshooting...................................................................................................................................341
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12.1.1 Failed to Ping the IP Address of the Remote Tunnel Interface...........................................................341
12.1.2 Troubleshooting Cases........................................................................................................................344
12.2 IPSec Troubleshooting.................................................................................................................................347
12.2.1 SAs Fail to Be Established Manually..................................................................................................347
12.2.2 SAs Fail to Be Established by Using IKE Negotiation.......................................................................351
12.2.3 IPSec Fails to Be Configured by Using an IPSec Policy Template....................................................358
12.2.4 NAT Traversal in IPSec Fails..............................................................................................................365
12.2.5 GRE over IPSec Fails..........................................................................................................................372
12.2.6 Troubleshooting Cases........................................................................................................................379
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1 Hardware
About This Chapter
1.1 Board Registration Troubleshooting
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1.1 Board Registration Troubleshooting
1.1.1 A Board Fails to Be Registered
Common Causes
This fault is commonly caused by one of the following:
lThe board is starting.
lThe board was reset.
Troubleshooting Flowchart
The troubleshooting roadmap is as follows:
lCheck whether the board is starting.
lCheck whether the board is in an unregistered state after the board has finished startup.
lCheck whether the board was reset. If the board was reset, locate the cause.
Figure 1-1 shows the troubleshooting flowchart.
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Figure 1-1 A board fails to be registered
A board
fails to be
registered
Was board
reset?
Locate fault
according to
instructions
Is fault
rectified?
Seek
technical
support
End
No
No
Yes
Yes
Yes
Is board
starting?
No
Wait for the board
to complete
startup
Yes
Troubleshooting Procedure
NOTE
Saving the results of each troubleshooting step is recommended. If troubleshooting fails to correct the fault,
you will have a record of your actions to provide to Huawei technical support personnel.
Procedure
Step 1 Check whether the board is starting.
A board takes several minutes to complete registration after power-on. This period is called the
startup time. The startup times for specific boards are follows:
lThe startup time of the SRU is less than 3 minutes. If the device restarts after the system
software is upgraded, the startup time is less than 5 minutes.
lThe startup time of an LPU is less than 5 minutes. If the LPU needs to synchronize an update
from the SRU, the startup time is less than 10 minutes.
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lIf the board is still within its startup time, wait until it starts.
lIf the board has exceeded its startup time, run the display device command to check the
board status. If the Register field of the board is displayed as Unregistered, go to step 2.
Step 2 Check whether the board was reset.
lRun the display reset-reason [ slot slot-id ] command. If no information about board
resetting is displayed, the board has never been registered. Connect the board to a terminal
with a serial cable and check whether the system software has been loaded to the board
correctly. For details, see Board Software Loading Troubleshooting.
lIf information about board resetting is displayed, rectify the fault according to the
instructions in the command output.
If the fault persists, go to step 3.
Step 3 Collect the following information and contact Huawei technical support personnel.
lResults of the preceding troubleshooting procedure
lConfiguration file, log file, and alarm file of the AR2200-S
----End
Relevant Alarms and Logs
Relevant Alarms
None.
Relevant Logs
None.
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2 System
About This Chapter
2.1 CPU Troubleshooting
2.2 Telnet Troubleshooting
2.3 SSH Troubleshooting
This chapter describes common causes of the fault that the user fails to log in to the server through
SSH, and provides the corresponding troubleshooting flowcharts and examples.
2.4 Mirroring Troubleshooting
This chapter describes common causes of mirroring faults, and provides the corresponding
troubleshooting flowcharts, troubleshooting procedures, alarms, and logs.
2.5 SNMP Troubleshooting
2.6 NQA Troubleshooting
2.7 NTP Troubleshooting
2.8 CWMP Troubleshooting
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2.1 CPU Troubleshooting
2.1.1 CPU Usage Is High
Common Causes
CPU usage is the percentage of the time during which the CPU executes codes to the total time
period. CPU usage is an important index to evaluate device performance.
To view CPU usage, run the display cpu-usage command. If you see that CPU usage exceeds
70%, CPU usage is high. A high CPU usage will cause service faults, for example, BGP route
flapping, frequent VRRP active/standby switchovers, and even failed device login.
High system CPU usage occurs when CPU usage of some tasks remains high. This fault is
commonly caused by one of the following:
lA large number of packets are sent to the CPU when loops or DoS packet attacks occur.
lSTP flapping frequently occurs and a large number of TC packets are received, causing the
device to frequently delete MAC address entries and ARP entries.
lThe device generates a large number of logs, consuming a lot of CPU resources.
Troubleshooting Flowchart
Figure 2-1 shows the troubleshooting flowchart.
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Figure 2-1 CPU usage is high
CPU usage is high
Seek technical
support
Is fault
rectified?
Is fault
rectified?
Is fault
rectified?
Analyze packet
features to filter out
attack packets
Suppress TC-BPDUs
Eliminate the loop
Collect log files and
contact the Huawei
technical support
personnel
End
Yes
No
No
No
No
Yes
Yes
Yes
No
No
No
Yes
Yes
Yes
Are a large
number of logs
generated?
Does a loop
occur on the
network?
Are a
large number of
TC packets
received?
Are a
large number of
packets sent to the
CPU?
Troubleshooting Procedure
NOTE
Saving the results of each troubleshooting step is recommended. If troubleshooting fails to correct the fault,
you will have a record of your actions to provide Huawei technical support personnel.
The following procedures can be performed in any sequence.
The command output in the following procedures varies based on the device model. The following
procedures describe how to view related information.
Procedure
Step 1 Check the names of tasks with a high CPU usage.
Run the display cpu-usage command to check the CPU usage of each task .
Record the names of tasks with CPU usage exceeding 70%.
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NOTE
CPU usage of 70% does not necessarily affect services. Services may not be affected when some tasks
consume 70% of CPU resources, but may be affected when some tasks consume 30% of CPU resources.
This outcome depends on the actual situation.
Step 2 Check whether a large number of packets are sent to the CPU.
Run the display cpu-defend statistics command to check statistics about the packets sent to the
CPU and focus on the Drop field.
<Huawei> display cpu-defend statistics all
-----------------------------------------------------------------------
Packet Type Pass Packets Drop Packets
-----------------------------------------------------------------------
8021X 0 0
arp-miss 1 0
arp-reply 5 0
arp-request 1450113 25597
bfd 0 0
bgp 0 0
dhcp-client 114693 136586
dhcp-server 0 0
dns 0 0
fib-hit 0 0
ftp 717 0
fw-dns 0 0
fw-ftp 0 0
fw-http 0 0
fw-rtsp 0 0
fw-sip 0 0
gvrp 0 0
http 798 0
hw-tacacs 0 0
icmp 10 0
igmp 0 0
ipsec 0 0
isis 0 0
lacp 0 0
lldp 33959 0
ntp 0 0
ospf 1569 0
pim 0 0
pppoe 0 0
radius 0 0
rip 0 0
snmp 0 0
ssh 0 0
stp 0 0
tcp 7671 0
telnet 71149 0
ttl-expired 656 0
udp-helper 0 0
unknown-multicast 6 0
unknown-packet 94189 0
vrrp 0 0
-----------------------------------------------------------------------
lIf the value of the Drop field of a certain type of packets is great and CPU usage is high,
packet attacks occur. Go to step 6.
lIf the value of the Drop field is within the specified range, go to step 3.
Step 3 Check whether a large number of TC packets are received.
If STP is enabled on a device, the device deletes MAC address entries and ARP entries when
receiving TC-BPDUs. If an attacker sends pseudo TC-BPDUs to attack the device, the device
will receive a large number of TC-BPDUs within a short period and frequently deletes MAC
address entries and ARP entries. As a result, the device CPU usage becomes high.
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Run the display stp command to check statistics about the received TC packets and TCN packets.
<Huawei> display stp interface Eth2/0/1
----[CIST][Port2(Ethernet2/0/1)][FORWARDING]----
Port Protocol :Enabled
Port Role :Designated Port
Port Priority :128
Port Cost(Dot1T ) :Config=auto / Active=199999
Designated Bridge/Port :4096.00e0-fc01-0005 / 128.2
Port Edged :Config=default / Active=disabled
Point-to-point :Config=auto / Active=true
Transit Limit :147 packets/hello-time
Protection Type :None
Port STP Mode :MSTP
Port Protocol Type :Config=auto / Active=dot1s
PortTimes :Hello 2s MaxAge 20s FwDly 15s RemHop 20
TC or TCN send :1
TC or TCN received :0
BPDU Sent :124008
TCN: 0, Config: 0, RST: 0, MST: 124008
BPDU Received :0
TCN: 0, Config: 0, RST: 0, MST: 0
lIf a large number of TC packets and TCN packets are received, run the stp tc-protection
command in the system view to suppress TC-BPDUs. After this command is used, only three
TC packets are processed within a Hello interval by default. Run the stp tc-protection
threshold command to set the maximum number of TC packets that can be processed. To
change the hello interval, run the stp timer hello command.
[Huawei] stp tc-protection
[Huawei] stp tc-protection threshold 5
[Huawei] stp timer hello 200
lIf a small number of TC packets are received, go to step 4.
Step 4 Check whether loops occur on the network.
When multiple interfaces of a device belong to the same VLAN, if a loop occurs between two
interfaces, packets are forwarded only between these interfaces in the VLAN. Consequently,
CPU usage of the device becomes high.
Run the display current-configuration command to check whether the device is enabled to
generate an alarm when MAC address flapping is detected.
#
loop-detect eth-loop alarm-only
#
lIf this function is not configured, run the loop-detect eth-loop alarm-only command to
configure this function. If a loop occurs on the network, an alarm is generated when two
interfaces of the device learn the same MAC address entry. For example:
Feb 22 2011 18:42:50 Huawei L2IFPPI/4/MAC_FLAPPING_ALARM:OID
1.3.6.1.4.1.2011.5.25.42.2.1.7.12The mac-address has flap value .
(L2IfPort=0,entPhysicalIndex=0, BaseTrapSeverity=4, BaseTrapProbableCause=549,
BaseTrapEventType=1, MacAdd=0000-c0a8-0101,vlanid=100,
FormerIfDescName=Ethernet1/0/0,CurrentIfDescName=Ethernet1/0/1,DeviceName=HUAWE
I)
Check the interface connection and networking information based on the alarm:
–If no ring network is required, shut down one of the two interfaces based on the networking
diagram.
–If the ring network is required, disable loop detection and enable loop prevention
protocols, such as STP.
lIf the loop-detect eth-loop alarm-only command is used on the device but no alarm is
generated, go to step 5.
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Step 5 Check whether a large number of logs are generated on the device.
The device generates diagnostic information or logs continuously in some cases, for example,
attacks occur on the device, an error occurs during device operation, or an interface frequently
alternates between Up and Down states. If the storage device is frequently read or written, CPU
usage becomes high.
Run the display logbuffer command to check whether a large number of logs are generated. If
a certain log is repeatedly generated, go to step 6.
Step 6 Collect the following information and contact Huawei technical support personnel:
lResults of the preceding troubleshooting procedure
lConfiguration files, log files, and alarm files of the device
----End
Relevant Alarms and Logs
Relevant Alarms
None
Relevant Logs
None
2.2 Telnet Troubleshooting
2.2.1 The User Fails to Log in to the Server Through Telnet
Common Causes
This fault is commonly caused by one of the following:
lThe route is unreachable, and the user cannot set up a TCP connection with the server.
lThe number of users logging in to the server reaches the upper threshold.
lAn ACL is configured in the VTY user interface view.
lThe access protocol specified in the VTY user interface view is incorrect. For example,
when the access protocol is configured to SSH through the protocol inbound ssh
command, the user cannot log in to the server through Telnet.
Troubleshooting Flowchart
Figure 2-2 shows the troubleshooting flowchart.
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Figure 2-2 Troubleshooting flowchart for the fault that the client fails to log in to the server
through Telnet
No
The user fails to log
in to the server through
Telnet
Can the client
successfully ping the
server?
Locate and
rectify the fault
End
Is the fault
rectified?
Yes
Increase the
maximum
number of users
allowed to log in
Is the fault
rectified?
Is the user access
type set to
all or telnet?
Is the fault
rectified?
Set the user
access type to all
or telnet
Does the IP address
of the user exist in the
ACL?
Is the fault
rectified?
Yes
Permit the IP
address of the
user in the ACL
Is the authentication
mode configured?
Is the fault
rectified?
Configure the
authentication
mode
Seek technical
support
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Are all the current
VTY channels in use?
Troubleshooting Procedure
NOTE
Saving the results of each troubleshooting step is recommended. If your troubleshooting fails to correct
the fault, you will have a record of your actions to provide Huawei technical support personnel.
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