Configuring System Message Logging

Restrictions for System Message Logging

■Logging messages to the console at a high rate can result in high CPU utilization and adversely affect how the switch operates.

Information About System Message Logging

System Message Logging

By default, a switch sends the output from system messages and debug privileged EXEC commands to a logging process. The logging process controls the distribution of logging messages to various destinations, such as the logging buffer, terminal lines, or a UNIX syslog server, depending on your configuration. The process also sends messages to the console.

Note: The syslog format is compatible with 4.3 BSD UNIX.

When the logging process is disabled, messages are sent only to the console. The messages are sent as they are generated, so message and debug output are interspersed with prompts or output from other commands. Messages appear on the console after the process that generated them has finished.

You can set the severity level of the messages to control the type of messages displayed on the consoles and each of the destinations. You can time-stamp log messages or set the syslog source address to enhance real-time debugging and management.

You can access logged system messages by using the switch command-line interface (CLI) or by saving them to a properly configured syslog server. The switch software saves syslog messages in an internal buffer.

You can remotely monitor system messages by viewing the logs on a syslog server or by accessing the switch through Telnet or through the console port.

System Log Message Format

System log messages can contain up to 80 characters and a percent sign (%), which follows the optional sequence number or time-stamp information, if configured. Messages appear in this format:

seq no:timestamp: %facility-severity-MNEMONIC:description

The part of the message preceding the percent sign depends on the setting of the service sequence-numbers, service timestamps log datetime, service timestamps log datetime [ localtime ] [ msec ] [ show-timezone ], or service timestamps log uptime global configuration command.

Table 53 System Log Message Elements
Element	Description
seq no:	Stamps log messages with a sequence number only if the service sequence-numbers global configuration command is configured. For more information, see Enabling and Disabling Sequence Numbers in Log Messages.
timestamp formats: mm/dd hh:mm:ss or hh:mm:ss (short uptime) or d h (long uptime)	Date and time of the message or event. This information appears only if the service timestamps log [ datetime \| log ] global configuration command is configured. For more information, see Enabling and Disabling Time Stamps on Log Messages.
facility	The facility to which the message refers (for example, SNMP, SYS, and so forth).
severity	Single-digit code from 0 to 7 that is the severity of the message.
MNEMONIC	Text string that uniquely describes the message.
description	Text string containing detailed information about the event being reported.

Log Messages

You can synchronize unsolicited messages and debug privileged EXEC command output with solicited device output and prompts for a specific console port line or virtual terminal line. You can identify the types of messages to be output asynchronously based on the level of severity. You can also configure the maximum number of buffers for storing asynchronous messages for the terminal after which messages are dropped.

When synchronous logging of unsolicited messages and debug command output is enabled, unsolicited device output appears on the console or printed after solicited device output appears or is printed. Unsolicited messages and debug command output appears on the console after the prompt for user input is returned. Therefore, unsolicited messages and debug command output are not interspersed with solicited device output and prompts. After the unsolicited messages appear, the console again displays the user prompt.

Message Severity Levels

Note: Specifying a level causes messages at that level and numerically lower levels to appear at the destination.

To disable logging to the console, use the no logging console global configuration command. To disable logging to a terminal other than the console, use the no logging monitor global configuration command. To disable logging to syslog servers, use the no logging trap global configuration command.

Table 54 describes the level keywords. It also lists the corresponding UNIX syslog definitions from the most severe level to the least severe level.

Table 54 Level Keywords
Level Keyword	Level	Description	Syslog Definition
emergencies	0	System unstable	LOG_EMERG
alerts	1	Immediate action needed	LOG_ALERT
critical	2	Critical conditions	LOG_CRIT
errors	3	Error conditions	LOG_ERR
warnings	4	Warning conditions	LOG_WARNING
notifications	5	Normal but significant condition	LOG_NOTICE
informational	6	Informational messages only	LOG_INFO
debugging	7	Debugging messages	LOG_DEBUG

The software generates these categories of messages:

■Error messages about software or hardware malfunctions, displayed at levels warnings through emergencies. These types of messages mean that the functionality of the switch is affected.

■Output from the debug commands, displayed at the debugging level. Debug commands are typically used only by the Technical Assistance Center.

■Interface up or down transitions and system restart messages, displayed at the notifications level. This message is only for information; switch functionality is not affected.

Configuring UNIX Syslog Servers

The next sections describe how to configure the UNIX server syslog daemon and how to define the UNIX system logging facility.

Logging Messages to a UNIX Syslog Daemon

Before you can send system log messages to a UNIX syslog server, you must configure the syslog daemon on a UNIX server. This procedure is optional.

Note: Some recent versions of UNIX syslog daemons no longer accept by default syslog packets from the network. If this is the case with your system, use the UNIX man syslogd command to decide what options must be added to or removed from the syslog command line to enable logging of remote syslog messages.

1. Add a line such as the following to the file /etc/syslog.conf:

local7.debug /usr/adm/logs/cisco.log

The local7 keyword specifies the logging facility to be used. The debug keyword specifies the syslog level. The syslog daemon sends messages at this level or at a more severe level to the file specified in the next field. The file must already exist, and the syslog daemon must have permission to write to it.

2. Create the log file by entering these commands at the UNIX shell prompt:

$ touch /var/log/cisco.log

$ chmod 666 /var/log/cisco.log

3. Make sure the syslog daemon reads the new changes:

$ kill -HUP `cat /etc/syslog.pid`

For more information, see the man syslog.conf and man syslogd commands on your UNIX system.

Table 55 lists the UNIX system facilities supported by the software. For more information about these facilities, consult the operator’s manual for your UNIX operating system.

Table 55 UNIX System Facilities
Facility Type Keyword	Description
auth	Authorization system
cron	Cron facility
daemon	System daemon
kern	Kernel
local0-7	Locally defined messages
lpr	Line printer system
mail	Mail system
news	USENET news
sys9-14	System use
syslog	System log
user	User process
uucp	UNIX-to-UNIX copy system

Default System Message Logging Configuration

Feature	Default Setting
System message logging to the console	Enabled.
Console severity	Debugging (and numerically lower levels).
Logging file configuration	No filename specified.
Logging buffer size	4096 bytes.
Logging history size	1 message.
Time stamps	Disabled.
Synchronous logging	Disabled.
Logging server	Disabled.
Syslog server IP address	None configured.
Configuration change logger	Disabled.
Server facility	Local7.
Server severity	Informational (and numerically lower levels).

How to Configure System Message Logging

Disabling Message Logging

Message logging is enabled by default. It must be enabled to send messages to any destination other than the console. When enabled, log messages are sent to a logging process, which logs messages to designated locations asynchronously to the processes that generated the messages.

Disabling the logging process can slow down the switch because a process must wait until the messages are written to the console before continuing. When the logging process is disabled, messages appear on the console as soon as they are produced, often appearing in the middle of command output.

	Command	Purpose
1.	configure terminal	Enters global configuration mode.
2.	no logging console	Disables message logging.
3.	end	Returns to privileged EXEC mode.

Setting the Message Display Destination Device

If message logging is enabled, you can send messages to specific locations in addition to the console. Beginning in privileged EXEC mode, use one or more of the following commands to specify the locations that receive messages:

	Command	Purpose
1.	configure terminal	Enters global configuration mode.
2.	logging buffered [ size ]	Logs messages to an internal buffer on the switch. The range is 4096 to 2147483647 bytes. The default buffer size is 4096 bytes. If the switch fails, the log file is lost unless you had previously saved it to flash memory. See Step 4. Note: Do not make the buffer size too large because the switch could run out of memory for other tasks. Use the show memory privileged EXEC command to view the free processor memory on the switch. However, this value is the maximum available, and the buffer size should not be set to this amount.
3.	logging host	Logs messages to a UNIX syslog server host. host— Specifies the name or IP address of the host to be used as the syslog server. To build a list of syslog servers that receive logging messages, enter this command more than once.
4.	logging file flash: filename [ max-file-size [ min-file-size ]] [ severity-level-number \| type ]	Stores log messages in a file in flash memory. ■ filename —Enters the log message filename. ■(Optional) max-file-size —Specifies the maximum logging file size. The range is 4096 to 2147483647. The default is 4096 bytes. ■(Optional) min-file-size— Specifies the minimum logging file size. The range is 1024 to 2147483647. The default is 2048 bytes. ■(Optional) severity-level-number \| type —Specifies either the logging severity level or the logging type. The severity range is 0 to 7. By default, the log file receives debugging messages and numerically lower levels.
5.	end	Returns to privileged EXEC mode.
6.	terminal monitor	Logs messages to a nonconsole terminal during the current session. Terminal parameter-setting commands are set locally and do not remain in effect after the session has ended. You must perform this step for each session to see the debugging messages.

Synchronizing Log Messages

	Command	Purpose
1.	configure terminal	Enters global configuration mode.
2.	line [ console \| vty ] line-number [ ending-line-number ]	Specifies the line to be configured for synchronous logging of messages. ■Use the console keyword for configurations that occur through the switch console port. ■Use the line vty line-number command to specify which vty lines are to have synchronous logging enabled. You use a vty connection for configurations that occur through a Telnet session. The range of line numbers is from 0 to 15. You can change the setting of all 16 vty lines at once by entering: line vty 0 15 Or you can change the setting of the single vty line being used for your current connection. For example, to change the setting for vty line 2, enter: line vty 2 When you enter this command, the mode changes to line configuration.
3.	logging synchronous [ level [ severity-level \| all ] \| limit number-of-buffers ]	Enables synchronous logging of messages. ■(Optional) level severity-level —Specifies the message severity level. Messages with a severity level equal to or higher than this value are printed asynchronously. Low numbers mean greater severity and high numbers mean lesser severity. The default is 2. ■(Optional) level all —Specifies that all messages are printed asynchronously regardless of the severity level. ■(Optional) limit number-of-buffers —Specifies the number of buffers to be queued for the terminal after which new messages are dropped. The range is 0 to 2147483647. The default is 20.
4.	end	Returns to privileged EXEC mode.

Enabling and Disabling Time Stamps on Log Messages

Command

Purpose

configure terminal

Enters global configuration mode.

service timestamps log uptime

service timestamps log datetime [ msec ] [ localtime ] [ show-timezone ]

Enables log time stamps.

The first command enables time stamps on log messages, showing the time since the system was rebooted.

The second command enables time stamps on log messages. Depending on the options selected, the time stamp can include the date, time in milliseconds relative to the local time-zone, and the time zone name.

end

Returns to privileged EXEC mode.

Enabling and Disabling Sequence Numbers in Log Messages

Because there is a chance that more than one log message can have the same time stamp, you can display messages with sequence numbers so that you can unambiguously see a single message. By default, sequence numbers in log messages are not displayed.

	Command	Purpose
1.	configure terminal	Enters global configuration mode.
2.	service sequence-numbers	Enables sequence numbers.
3.	end	Returns to privileged EXEC mode.

Defining the Message Severity Level

You can limit messages displayed to the selected device by specifying the severity level of the message, which are described in Table 2.

	Command	Purpose
1.	configure terminal	Enters global configuration mode.
2.	logging console level	Limits messages logged to the console. By default, the console receives debugging messages and numerically lower levels.
3.	logging monitor level	Limits messages logged to the terminal lines. By default, the terminal receives debugging messages and numerically lower levels.
4.	logging trap level	Limits messages logged to the syslog servers. By default, syslog servers receive informational messages and numerically lower levels.
5.	end	Returns to privileged EXEC mode.

Limiting Syslog Messages Sent to the History Table and to SNMP

If you enabled syslog message traps to be sent to an SNMP network management station by using the snmp-server enable trap global configuration command, you can change the level of messages sent and stored in the switch history table. You also can change the number of messages that are stored in the history table.

Messages are stored in the history table because SNMP traps are not guaranteed to reach their destination. By default, one message of the level warning and numerically lower levels are stored in the history table even if syslog traps are not enabled.

When the history table is full (it contains the maximum number of message entries specified with the logging history size global configuration command), the oldest message entry is deleted from the table to allow the new message entry to be stored.

	Command	Purpose
1.	configure terminal	Enters global configuration mode.
2.	logging history level	Changes the default level of syslog messages stored in the history file and sent to the SNMP server. By default, warnings, errors, critical, alerts, and emergencies messages are sent.
3.	logging history size number	Specifies the number of syslog messages that can be stored in the history table. The default is to store one message. The range is 0 to 500 messages.
4.	end	Returns to privileged EXEC mode.

Enabling the Configuration-Change Logger

You can enable a configuration logger to keep track of configuration changes made with the command-line interface (CLI). When you enter the logging enable configuration-change logger configuration command, the log records the session, the user, and the command that was entered to change the configuration. You can configure the size of the configuration log from 1 to 1000 entries (the default is 100).

	Command	Purpose
1.	configure terminal	Enters global configuration mode.
2.	archive	Enters archive configuration mode.
3.	log config	Enters configuration-change logger configuration mode.
4.	logging enable	Enables configuration change logging.
5.	logging size entries	(Optional) Configures the number of entries retained in the configuration log. The range is from 1 to 1000. The default is 100. Note: When the configuration log is full, the oldest log entry is removed each time a new entry is entered.
6.	end	Returns to privileged EXEC mode.

Configuring the UNIX System Logging Facility

When sending system log messages to an external device, you can cause the switch to identify its messages as originating from any of the UNIX syslog facilities.

	Command	Purpose
1.	configure terminal	Enters global configuration mode.
2.	logging host	Logs messages to a UNIX syslog server host by entering its IP address. To build a list of syslog servers that receive logging messages, enter this command more than once.
3.	logging trap level	Limits messages logged to the syslog servers. Be default, syslog servers receive informational messages and lower.
4.	logging facility facility-type	Configures the syslog facility. The default is local7.
5.	end	Returns to privileged EXEC mode.

Monitoring and Maintaining the System Message Log

Command	Purpose
show logging	Displays logging messages.
show archive log config	Displays the configuration log.

Configuration Examples for the System Message Log

System Message: Example

This example shows a partial switch system message:

00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up

00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet1/17, changed state to up

00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet1/18, changed state to up

00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down

00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/17, changed state to down 2

*Mar 1 18:46:11: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)

18:47:02: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)

*Mar 1 18:48:50.483 UTC: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)

Logging Display: Examples

This example shows part of a logging display with the service timestamps log datetime global configuration command enabled:

*Mar 1 18:46:11: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)

This example shows part of a logging display with the s ervice timestamps log uptime global configuration command enabled:

00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up

This example shows part of a logging display with sequence numbers enabled:

000019: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)

Enabling the Logger: Example

This example shows how to enable the configuration-change logger and to set the number of entries in the log to 500.

Switch(config)# archive

Switch(config-archive)# log config

Switch(config-archive-log-cfg)# logging enable

Switch(config-archive-log-cfg)# logging size 500

Switch(config-archive-log-cfg)# end

Configuration Log Output: Example

This is an example of output for the configuration log:

Switch# show archive log config all

idx sess user@line Logged command

38 11 unknown user@vty3 |no aaa authorization config-commands

39 12 unknown user@vty3 |no aaa authorization network default group radius

40 12 unknown user@vty3 |no aaa accounting dot1x default start-stop group radius

41 13 unknown user@vty3 |no aaa accounting system default

42 14 temi@vty4 |interface GigabitEthernet4/0/1

43 14 temi@vty4 | switchport mode trunk

44 14 temi@vty4 | exit

45 16 temi@vty5 |interface FastEthernet5/0/1

46 16 temi@vty5 | switchport mode trunk

47 16 temi@vty5 | exit

Additional References

The following sections provide references related to switch administration:

Related Topic	Document Title
Cisco IOS basic commands Cisco IOS system management commands	Cisco IOS Configuration Fundamentals Command Reference
Syslog server configuration steps	Configuring the UNIX System Logging Facility

Standards

Standards	Title
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.	—

MIBs

MIBs	MIBs Link
—	To locate and download MIBs using Cisco IOS XR software, use the Cisco MIB Locator found at the following URL and choose a platform under the Cisco Access Products menu: http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs

RFCs	Title
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.	—

Technical Assistance

Description	Link
The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.	http://www.cisco.com/techsupport

Cisco Industrial Ethernet 4000, 4010 and 5000 Switch Software Configuration Guide

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Book Title

Cisco Industrial Ethernet 4000, 4010 and 5000 Switch Software Configuration Guide

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