The common fault diagnostic commands include display, reset, ping, and tracert commands. Additionally, alarms, logs, and packet header obtaining are effective methods to locate faults.
- 8.1 display Commands
Using display commands and understanding command functions are essential skills of maintenance engineers. - 8.2 reset Commands
reset commands are used to clear statistics. These commands help you quickly locate faults. - 8.3 Ping and Tracert
This section describes how to use Ping and Tracert commands to check network connectivity and locate network faults. The Ping command checks network connectivity and host reachability and the Tracert command tracks the gateways that packets pass through from the source host to the destination host. - 8.4 Alarms
- 8.5 Logs
- 8.6 Mirroring (V200R003&V200R005)
Remote mirroring is used to obtain packet headers. The device copies packet headers from the mirrored port to an observing port . - 8.7 Mirroring (V200R006 and Later Versions)
Remote mirroring is used to obtain packet headers. The device copies packet headers to an observing port .
8.1 display Commands
Using display commands and understanding command functions are essential skills of maintenance engineers.
8.1.1 Overview
The display commands provide the following information:
- Current device status
- Neighbor device information
- Overall network information
- Network fault location
The display commands can be executed in any view.
The following is an example of display commands:
<Huawei> display ?
aaa AAA
access-user User access
accounting-scheme Accounting scheme
acl <Group> acl command group
actual Current actual
alarm Alarm
antenna Current antenna that outputting radio
anti-attack Specify anti-attack configurations
ap <Group> ap command group
---- More ----
NOTE: After you enter display ?, the system displays all the keywords behind display. More keywords can be added behind these displayed keywords.
Different device models or versions support different features. The keywords actually displayed may be different from the preceding example.
This section involves only commonly used display commands. For more display commands, see the Huawei Wireless Access Points Command Reference.
8.1.2 Regular Expression in display Commands
When running the display command to check the command output, you can use the regular expression (specifying the rule to display) to filter the output information and locate needed information quickly.
Regular Expressions
A regular expression is a mode matching tool. It consists of common characters (such as letters from a to z) and special characters (called meta-characters). The regular expression is a template according to which you can search for the required string.
Searches for and obtains a sub-string that matches a rule in the string.
Substitutes a string based on a certain matching rule.
The regular expression consists of common characters and special characters.
Common characters
Common characters are used to match themselves in a string, including all upper-case and lower-case letters, digits, punctuations, and special symbols. For example, a matches the letter "a" in "abc", 202 matches the digit "202" in "202.113.25.155", and @ matches the symbol "@" in "xxx@xxx.com".
Special characters
Special characters are used together with common characters to match the complex or special string combination. Table 8-1 describes special characters and their syntax.
Table 8-1 Description of special charactersSpecial Characters
Function
Example
\
Defines an escape character, which is used to mark the next character (common or special) as the common character.
\* matches "*".
^
Matches the starting position of the string.
^10 matches "10.10.10.1" instead of "20.10.10.1".
$
Matches the ending position of the string.
1$ matches "10.10.10.1" instead of "10.10.10.2".
*
Matches the preceding element zero or more times.
10* matches "1", "10", "100", "1000", and so on.
(10)* matches "null", "10", "1010", "101010", and so on.
+
Matches the preceding element one or more times.
10+ matches "10", "100", "1000", and so on.
(10)+ matches "10", "1010", "101010", and so on.
?
Matches the preceding element zero or one time.
NOTE:Huawei datacom devices do not support regular expressions with ?. When regular expressions with ? are entered on Huawei datacom devices, helpful information is provided.
10? matches "1" or "10".
(10)? matches "null" or "10".
.
Matches any single character.
0.0 matches "0x0", "020", and so on.
.oo. matches "book", "look", "tool", and so on.
()
Defines a subexpression, which can be null. Both the expression and the subexpression should be matched.
100(200)+ matches "100200", "100200200", and so on.
x|y
Matches x or y.
100|200 matches "100" or "200".
1(2|3)4 matches "124" or "134", instead of "1234", "14", "1224", and "1334".
[xyz]
Matches any single character in the regular expression.
[123] matches the character 2 in "255".
[^xyz]
Matches any character that is not in the regular expression.
[^123] matches any character except for "1", "2", and "3".
[a-z]
Matches any character within the specified range.
[0-9] matches any character ranging from 0 to 9.
[^a-z]
Matches any character beyond the specified range.
[^0-9] matches all non-numeric characters.
_
Matches a comma ",", left brace "{", right brace "}", left parenthesis "(", and right parenthesis ")".
Matches the starting position of the input string.
Matches the ending position of the input string.
Matches a space.
_2008_ matches "space 2008 space", ",2008,", "{2008}", "(2008)", "{2008)", and "(2008}".
_2008 matches "space 2008", ",2008", "{2008","(2008".
_2008 matches "2008 space", "2008,", "2008{","2008)".
NOTE: Unless otherwise specified, all the characters in the preceding table must be printable characters.
Degeneration of special characters
Certain special characters, when placed at certain positions in a regular expression, degenerate to common characters.
The special characters following "\" match special characters themselves.
The special characters "*", "+", and "?" are placed at the starting position of the regular expression. For example, +45 matches "+45" and abc(*def) matches "abc*def".
The special character "^" is placed at any position except for the start of the regular expression. For example, abc^ matches "abc^".
The special character "$" is placed at any position except for the end of the regular expression. For example, 12$2 matches "12$2".
A right parenthesis ")" or right bracket "]" is not paired with a corresponding left parenthesis "(" or bracket "[". For example, abc) matches "abc)" and 0-9] matches "0-9]".
NOTE: Unless otherwise specified, degeneration rules also apply when the preceding regular expressions are subexpressions within parentheses.
Combination of common and special characters
In actual usage, regular expressions combine multiple common and special characters to match certain strings.
Specifying a Filtering Mode in a Command
NOTE: The device uses a regular expression to implement the pipe character filtering function. A display command supports the pipe character only when there is excessive output information.
When filtering conditions are set to query output information, the first line of the command output starts with the entire regular expression but not the string to be filtered.
Some commands can carry the keyword | count to display the number of matching entries. The keyword | count can be used together with other keyword.
Three filtering modes are provided for commands that support regular expressions.
| begin regular-expression: displays all the lines beginning with the line that matches the regular expression.
Filter the character strings to be entered until the specified case-sensitive character string is displayed. All the character strings following this specified character string are displayed on the screen.
| exclude regular-expression: displays all the lines that do not match the regular expression.
If the character strings to be entered do not contain the specified case-sensitive character string, they are displayed on the screen. Otherwise, they are filtered.
| include regular-expression: displays all the lines that match the regular expression.
If the character strings to be entered contain the specified case-sensitive character string, they are displayed on the screen. Otherwise, they are filtered.
NOTE: The value of regular-expression is a string of 1 to 255 characters. If regular-expression contains special characters, to interpret them literally, add a backslash "\" before the characters.
The following examples describe how to specify a filter mode in a command.
Example 1: Run the display interface brief command to display all the lines that do not match the regular expression GigabitEthernet|NULL|Wlan-Radio. GigabitEthernet|NULL|Wlan-Radio matches GigabitEthernet, NULL or Wlan-Radio.
<Huawei> display interface brief | exclude GigabitEthernet|NULL|Wlan-RadioPHY: Physical *down: administratively down (l): loopback (s): spoofing (e): ETHOAM down (d): Dampening Suppressed InUti/OutUti: input utility/output utility Interface PHY Protocol InUti OutUti inErrors outErrors Vlanif10 down down -- -- 0 0 Vlanif2001 up up -- -- 0 0
Example 2: Run the display current-configuration command to display all the lines that match the regular expression vlan.
<Huawei> display current-configuration | include vlan
vlan batch 10 2001 port trunk allow-pass vlan 2001
NOTE: The preceding information is used for reference only.
8.1.3 Common display Commands
The device provides various display commands to display hardware, interface, and software information. The information helps you locate various faults.
The following table lists the commands used to collect fault information.
Item | Command | Description |
|---|---|---|
Basic information | display diagnostic-information | This command collects basic system information. It displays outputs of multiple display commands, including display version and display current-configuration. This command is necessary for any network problems. Executing this command takes a long time. You can press Ctrl+C to pause diagnosis information display on screen. |
Interface information | display interface | This command displays interface information to help you analyze cause of interface interconnection failures and check statistics on lost packets. |
Versions | display version | Version information is important for device fault location. This command displays versions of the system software, uBoot, MPU, as well as sizes of storage devices. |
Patch information | display patch-information | This command displays current patch information, including the patch package version and patch package name. |
Electronic label information | display elabel | Electronic labels identify information about hardware components of a device. This command displays electronic labels of cards on a device. |
Device status | display health | This command displays the temperature, power supply information, power, CPU usage, memory usage, and storage medium usage of a device. |
Current configurations | display current-configuration | This command displays all configuration information on a device. You can specify a regular expression to obtain the required configuration information. |
Saved configurations | display saved-configuration | If a device has started but is not working properly, run the display saved-configuration command to check the startup files specified by the startup saved-configuration command. Run the display saved-configuration last command to check the configuration saved last time. Run the display saved-configuration time command to check the last time when the configuration is saved. |
Time | display clock | This command displays the current system date and time. |
User logs | display logfile buffer | Executing this command in the diagnostic view can display user logs in the log buffer. |
Diagnostic log | display diag-logfile buffer | Executing this command in the diagnostic view can display user logs in the log buffer. |
Alarms | display trapbuffer | This command displays information recorded in the trap buffer. |
Memory usage | display memory-usage | This command displays memory usage of the device. |
CPU usage | display cpu-usage | This command displays CPU usage of the device. |
8.2 reset Commands
reset commands are used to clear statistics. These commands help you quickly locate faults.
8.2.1 Overview
reset commands include:
- Commands used for resetting
- Commands used for clearing statistics
This section involves the reset commands clearing statistics.
8.2.2 reset Commands Clearing Packet Statistics
reset counters interface and reset ip statistics are often used to clear packet statistics displayed in the display interface and display ip interface command output.
- The display interface command provides counters to collect statistics on sent and received Layer 2 packets. The reset counters interface command resets these counters.
- The display ip interface command provides counters to collect statistics on sent and received Layer 3 packets. The reset ip statistics command resets these counters.
8.2.3 Using reset Commands
Context
When you use the ping command to test link connectivity, you also need to run the display interface or display ip interface command to check whether packets are correctly sent and received on interfaces and whether a CRC error occurs. Then you can locate the interface where the fault occurs.
The display interface or display ip interface command output shows packet statistics generated after the device starts or the counter is reset; therefore, the packet statistics may contain unnecessary information that interferes with fault location.
To collect packet statistics accurately, perform the following operations:
Procedure
- Run the reset counters interface or reset ip statistics command to clear existing packet statistics.
- Run the ping command to enable router interfaces to send and receive packets.
- Run the display interface or display ip interface command to view the statistics.
Example
For example, after you run the display interface gigabitEthernet 0/0/0 command, the following statistics are displayed:
Input: 736 packets, 344842 bytes
Unicast: 0, Multicast: 714
Broadcast: 22, Jumbo: 0
Discard: 0, Total Error: 0
CRC: 0, Giants: 0
Jabbers: 0, Throttles: 0
Runts: 0, Symbols: 0
Ignoreds: 0, Frames: 0
Output: 2911 packets, 514228 bytes
Unicast: 0, Multicast: 2910
Broadcast: 1, Jumbo: 0
Discard: 0, Total Error: 0
Collisions: 0, ExcessiveCollisions: 0
Late Collisions: 0, Deferreds: 0 If the value of Total Error is not 0, there is an error in packet sending and receiving.
To check when the error occurs, run the reset counters interface gigabitEthernet 0/0/0 command to clear existing statistics, use the ping command to send ping packets, and run the display interface gigabitEthernet 0/0/0 command to view new statistics. If the Total Error value is still not 0, the error may need to be rectified.
8.3 Ping and Tracert
This section describes how to use Ping and Tracert commands to check network connectivity and locate network faults. The Ping command checks network connectivity and host reachability and the Tracert command tracks the gateways that packets pass through from the source host to the destination host.
Introduction to the Ping Command
Based on the Internet Control Message Protocol (ICMP), the Ping command is used to check network connectivity and host reachability. The source sends an ICMP Echo Request message to the destination, and determines reachability. The source determines the quality of the link from which the destination is reachable based on the number of sent ICMP Echo Request messages and received ICMP Echo Response messages, and the round-trip time (RTT) of ping packets.
Ping Command Format
NOTE: Huawei Wireless Access Points Command Reference provides detailed description of command parameters and usage. Here lists only some commonly used parameters and their descriptions.
ping [ ip ] [ -a source-ip-address | -c count | -f | -s packetsize | -t timeout ] *host
-a: specifies the source IP address for sending Echo Request messages. If no source IP address is specified, the IP address of the outbound interface is used as the source IP address.
-c: specifies the count for sending Echo Request messages. The default value is 5. You can increase the number of outgoing packets to detect the network quality based on the packet loss ratio.
-f: indicates that packets are not fragmented when they are sent. The device discards the packets if the packet size exceeds the MTU.
-s: specifies the length of an Echo Request message without the IP header and ICMP header.
-t: specifies the timeout interval of Echo Response messages. You can set a larger timeout interval if the network is unstable. The default value is 2s. If the device receives no Echo Request message, it determines that the destination is unreachable.
host: indicates an IP address or a domain name. If it is a domain name, the device performs DNS resolution and displays the resolved IP address.
NOTE: You can use the parameters -s and -f simultaneously to test the path MTU (PMTU). For example, if the ping operation succeeds when the parameter -s is set to 1472 but fails when the parameter is set to 1473, the PMTU is 1500, which is the total sum of 1472, 20 (IP header), and 8 (ICMP header).
The ping function varies with the operating system of a PC. The Windows operating system is used as an example.
ping [ -n number ] [ -t ] [ -l number ] [ -f ] [ -a ] ip-address
-n: specifies the number of ping packets. The default value is 5.
-t: indicates that the source sends Echo Request messages to the destination continuously until manual operations are involved. You can press Ctrl+Break to temporarily stop the ping command and view the statistics, and press Ctrl+C to end the ping operation.
-l: specifies the number of bytes of data in ping packets. The value ranges from 0 to 65500.
-f: indicates that packets are not fragmented when they are sent. The device discards the packets if the packet size exceeds the MTU.
-a: indicates that the device resolves an IP address into a host name.
Description of the Ping Command Output
<Huawei> ping 100.135.18.118
PING 100.135.18.118: 56 data bytes, press CTRL_C to break
Reply from 100.135.18.118: bytes=56 Sequence=1 ttl=255 time=1 ms
Reply from 100.135.18.118: bytes=56 Sequence=2 ttl=255 time=1 ms
Reply from 100.135.18.118: bytes=56 Sequence=3 ttl=255 time=2 ms
Reply from 100.135.18.118: bytes=56 Sequence=4 ttl=255 time=1 ms
Reply from 100.135.18.118: bytes=56 Sequence=5 ttl=255 time=2 ms
--- 100.135.18.118 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 1/1/2 ms In this example:
The device sends five ping packets and receives response for all the five packets.
The ping packets use the default size, 56 bytes.
The TTL value is 255, indicating that the source is directly connected to the destination.
The time is 1 ms, indicating that the device receives an Echo Response message 1 ms after it sends an Echo Request message. This parameter can be used as a reference to determine whether the network is congested.
The device sends five ping packets by default. You can set a larger value of -c to accurately detect the network status. The device determines the network status based on the number of ping packets returned.
Fault Description | Possible Cause |
|---|---|
All packets can reach the destination but require a long time. | The intermediate network is unstable. QoS is deployed on the gateway, which lowers the forwarding speed. |
No packet can reach the destination. | Services on the network are interrupted due to device or cable faults. The firewall on the intermediate network discards ICMP packets. A loop occurs on the network and packets are discarded when the TTL value is reduced to 1. Packets are delayed due to network congestion. |
Some packets cannot reach the destination. | Some ping packets are discarded on the unstable network. Load balancing is configured on the intermediate network and some ping packets are discarded on one path. Packet flooding attacks. |
Introduction to the Tracert Command
The Ping command checks whether the destination host is reachable and the Tracert command tracks the gateways that packets pass through from the source host to the destination host. This helps check network connectivity and locate network faults. The tracert process is as follows:
The source host sends a UDP packet with TTL 1.
The first hop sends back an error ICMP packet, indicating that the packet cannot be sent due to TTL timeout.
The source host then sends a packet with TTL 2.
The second hop drops the packet and sends an ICMP TTL-expired packet.
This process proceeds until the packet reaches the destination host. The source host obtains the path to the destination host based on the source IP addresses of TTL-expired packets.
Tracert Command Format
NOTE: Huawei Wireless Access Points Command Reference provides detailed description of command parameters and usage. Here lists only some commonly used parameters and their descriptions.
tracert [ -a source-ip-address | -f first-ttl | -m max-ttl | -q nqueries | -w timeout ] *host
-a: specifies the source address. If this parameter is not specified, the IP address of the outbound interface is used as the source IP address of outgoing packets.
-f: specifies the initial TTL. If the number of hops is smaller than the initial TTL, the source host receives no TTL-expired packet. If a maximum TTL is set, the initial TTL must be smaller than the maximum TTL.
-m: specifies the maximum TTL. The maximum TTL is usually set to the number of hops through which a Tracert packet passes. If an initial TTL is set, the maximum TTL must be larger than the initial TTL.
-q: specifies the number of UDP packets sent each time. You can increase this value to ensure that UDP packets can reach the destination host.
-w: sets the timeout interval of Response messages. If a gateway sends a message indicating TTL timeout, " * " is displayed. You are advised to increase the timeout interval when the network is unstable and the transmission speed is low.
host: indicates an IP address or a domain name. If it is a domain name, the device performs DNS resolution and displays the resolved IP address.
The tracert function varies with the operating system of a PC. The Windows operating system is used as an example for illustration.
tracert [ -d ] [ -h maximum_hops ] [ -j host-list ] [ -w timeout ] ip-address
-d: indicates that the host name is not resolved.
-h: specifies the maximum TTL.
-j: specifies the loose source address routing list.
-w: sets the timeout interval of UDP packets, in milliseconds.
Description of the Tracert Command Output
<Huawei> tracert 100.135.18.118
traceroute to 100.135.18.118(100.135.18.118), max hops: 30 ,packet length: 40,press CTRL_C to break
1 192.168.200.100 10 ms 2 ms 2 ms
2 * * *
3 100.135.18.118 10 ms 1 ms 2 msInformation displayed in a line includes the number, IP address where the packet reaches, and three response time. * * * is displayed in the second line, indicating that the ping and tracert operations are not supported on this node.
The Ping command can only determine whether the destination is reachable, whereas the Tracert command can detect potential loops on a network. If you track an address and the same address is displayed multiple times, a route loop occurs.
8.4 Alarms
When a device becomes faulty or works abnormally, the device system generates an alarm according to the types of the fault and faulty module. The system stores the alarm to the alarm buffer and generates logs. If a network management system (NMS) is configured, the device system also sends a trap to the NMS through the Simple Network Management Protocol (SNMP). In addition, the system is capable of detecting changes in operation environment. When a requirement for operation conditions cannot be met, the system generates an alarm.
To view alarm information, enable alarm debugging to display alarm information on the terminal. Alarm information is also stored in the alarm buffer, so you can use commands to view all alarms in the alarm buffer.
Alarms are classified into:
Fault alarms: generated when hardware faults or exceptions of key functions occur.
Recovery alarms: generated when faulty devices or abnormal functions recover.
Event alarms: generated when the user needs to be prompted.
- Display alarms on the graphic user interface (GUI) of the NMS.
- Run the display trapbuffer [ size value ] command to view alarms in the alarm buffer. The displayed alarms vary according to the value field. If the actual number of alarms is smaller than the specified number of alarms to be displayed, the actual number of alarms are displayed.
8.5 Logs
During device operation, the log module records operations and events on the device. The recorded operations and events are log messages.
The generated logs can be viewed through the Console port or Telnet, or stored to the log server through the syslog protocol.
The syslog protocol is transmitted through UDP port 514. Any UDP datagram on port 514 is recorded in the log.
- Display logs on the GUI of the NMS.
- Run the display logbuffer [ size value | module module-name | level severity ] * command to view logs in the log buffer.
8.6 Mirroring (V200R003&V200R005)
Remote mirroring is used to obtain packet headers. The device copies packet headers from the mirrored port to an observing port .
The device cannot analyze packet headers except that a computer with the packet analysis software installed or a tester is connected to the observing port. The commonly used packet analysis software is WireShark, and most testers have the packet analysis function.
NOTE: The packets captured for troubleshooting may contain secure communication information. Therefore, Huawei does not capture packets for you. You must capture packets legally and with permission. Ensure that your customers' privacy is protected when collecting communication information.
Mirroring Packet Headers to an Observing Port
Packet headers are copied from the mirrored port to an observing port. As shown in Figure 8-1, the incoming packets on BSS1 are captured to GE0/0/0, and the observing device directly connected to GE0/0/0 analyzes the packet headers.
The procedure is as follows:
Set GE0/0/0 on the AP as an observing port.
<Huawei> system-view [Huawei] sysname AP [AP] observe-port interface gigabitethernet 0/0/0
Set BSS1 on the AP as a mirrored port and set the mirroring direction to inbound.
[AP] interface wlan-bss 1 [AP-Wlan-Bss1] mirror to observe-port inbound [AP-Wlan-Bss1] quit [AP] quit
8.7 Mirroring (V200R006 and Later Versions)
Remote mirroring is used to obtain packet headers. The device copies packet headers to an observing port .
The device cannot analyze packet headers except that a computer with the packet analysis software installed or a tester is connected to the observing port. The commonly used packet analysis software is WireShark, and most testers have the packet analysis function.
NOTE: The packets captured for troubleshooting may contain secure communication information. Therefore, Huawei does not capture packets for you. You must capture packets legally and with permission. Ensure that your customers' privacy is protected when collecting communication information.
Mirroring Packet Headers to an Observing Port
Packet headers are copied from the VAP air port to an observing port. As shown in Figure 8-2, the incoming packets on VAP air port are captured to GE0/0/0, and the observing device directly connected to GE0/0/0 analyzes the packet headers.
The procedure is as follows:
Set GE0/0/0 on the AP as an observing port.
<Huawei> system-view [Huawei] sysname AP [AP] observe-port interface gigabitethernet 0/0/0
Configure the VAP-based mirroring function on the AP and set the mirroring direction to inbound.
[AP] mirror vap to observe-port inbound radio-id 0 ssid office01 [AP] quit
