Catalyst 4500 Series Switch Software Configuration Guide, IOS XE 3.6.xE and IOS 15.2(2)Ex

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 are displayed 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 ] command or the
service timestamps log uptime global configuration command.

Table 61-1 describes the elements of syslog messages.

This example shows a partial switch system message:

Default System Message Logging Configuration

Table 61-2 shows the default system message logging configuration.

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.

To disable message logging, perform this task:

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 are displayed on the console as soon as they are produced, often appearing in the middle of command output.

The logging synchronous global configuration command also affects the display of messages to the console. When this command is enabled, messages appear only after you press Return. For more information, see the “Synchronizing Log Messages” section.

To reenable message logging after it has been disabled, use the logging on global configuration command.

Setting the Message Display Destination Device

If message logging is enabled, you can send messages to specific locations in addition to the console.

To specify the locations that receive messages, perform this task, beginning in privileged EXEC mode:

The logging buffered global configuration command copies logging messages to an internal buffer. The buffer is circular, so newer messages overwrite older messages after the buffer is full. To display the messages that are logged in the buffer, use the show logging privileged EXEC command. The first message displayed is the oldest message in the buffer. To clear the contents of the buffer, use the
clear logging privileged EXEC command.

To disable logging to the console, use the no logging console global configuration command. To disable logging to a file, use the no logging file [ severity-level-number | type ] global configuration command.

Synchronizing 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 printed. Unsolicited messages and debug command output appears on the console after the prompt for user input is returned. Unsolicited messages and debug command output are not interspersed with solicited device output and prompts. After the unsolicited messages are displayed, the console again displays the user prompt.

To configure synchronous logging, perform this task:

To disable synchronization of unsolicited messages and debug output, use the
no logging synchronous [ level severity-level | all ] [ limit number-of-buffers ] line configuration command.

Enabling and Disabling Timestamps on Log Messages

Note By default, log messages are not time-stamped.

To enable time-stamping of log messages, perform this task:

To disable time-stamps for both debug and log messages, use the no service timestamps global configuration command.

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

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

Enabling and Disabling Sequence Numbers in Log Messages (Optional)

Because more than one log message can have the same timestamp, you can display messages with sequence numbers so that you can unambiguously refer to a single message. By default, sequence numbers in log messages are not displayed.

To enable sequence numbers in log messages, perform this task, which is optional.

To disable sequence numbers, use the no service sequence-numbers global configuration command.

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

Defining the Message Severity Level (Optional)

You can limit messages displayed to the selected device by specifying the severity level of the message, which are described in Table 61-3 .

To define the message severity level, perform this task:

Note Specifying a level causes messages at that level and numerically lower levels to be displayed 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 61-3 describes the level keywords. It also lists the corresponding UNIX syslog definitions from the most severe level to the least severe level.

The software generates four other 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. For information on how to recover from these malfunctions, see the system message guide for this release.
• 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.
• Reload requests and low-process stack messages, displayed at the informational level. This message is only for information; switch functionality is not affected.

Limiting Syslog Messages Sent to the History Table and to SNMP (Optional)

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 (see Table 61-3) are stored in the history table even if syslog traps are not enabled.

To change the level and history table size defaults, perform this task:

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.

To return the logging of syslog messages to the default level, use the no logging history global configuration command. To return the number of messages in the history table to the default value, use the no logging history size global configuration command.

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 applies to 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.

Log in as root, and perform these steps:

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

The local7 keyword specifies the logging facility to be used; see Table 61-4 for information on the facilities. The debug keyword specifies the syslog level; see Table 61-3 for information on the severity levels. 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.

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

Step 3 Ensure that the syslog daemon reads the new changes:

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

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.

To configure UNIX system facility message logging, perform this task (which is optional):

To remove a syslog server, use the no logging host global configuration command, and specify the syslog server IP address. To disable logging to syslog servers, enter the no logging trap global configuration command.

Table 61-4 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.