Configuring System Message Logging

This chapter contains the following sections:

Information About System Message Logging

You can use system message logging to control the destination and to filter the severity level of messages that system processes generate. You can configure logging to terminal sessions, a log file, and syslog servers on remote systems.

System message logging is based on RFC 3164. For more information about the system message format and the messages that the device generates, see the Cisco NX-OS System Messages Reference.

By default, the Cisco Nexus device outputs messages to terminal sessions.

By default, the switch logs system messages to a log file.

The following table describes the severity levels used in system messages. When you configure the severity level, the system outputs messages at that level and lower.

Table 1. System Message Severity Levels

Level

Description

0 – emergency

System unusable

1 – alert

Immediate action needed

2 – critical

Critical condition

3 – error

Error condition

4 – warning

Warning condition

5 – notification

Normal but significant condition

6 – informational

Informational message only

7 – debugging

Appears during debugging only

The switch logs the most recent 100 messages of severity 0, 1, or 2 to the NVRAM log. You cannot configure logging to the NVRAM.

You can configure which system messages should be logged based on the facility that generated the message and its severity level.

Syslog Servers

Syslog servers run on remote systems that are configured to log system messages based on the syslog protocol. You can configure the Cisco Nexus Series switch to send logs to up to eight syslog servers.

To support the same configuration of syslog servers on all switches in a fabric, you can use Cisco Fabric Services (CFS) to distribute the syslog server configuration.


Note

When the switch first initializes, messages are sent to syslog servers only after the network is initialized.

Guidelines and Limitations for System Message Logging

System message logging has the following configuration guidelines and limitations:

  • System messages are logged to the console and the logfile by default.

Default Settings for System Message Logging

The following table lists the default settings for system message logging parameters.

Table 2. Default System Message Logging Parameters

Parameters

Default

Console logging

Enabled at severity level 2

Monitor logging

Enabled at severity level 2

Log file logging

Enabled to log messages at severity level 5

Module logging

Enabled at severity level 5

Facility logging

Enabled

Time-stamp units

Seconds

Syslog server logging

Disabled

Syslog server configuration distribution

Disabled

Configuring System Message Logging

Configuring System Message Logging to Terminal Sessions

You can configure the switch to log messages by their severity level to console, Telnet, and Secure Shell sessions.

By default, logging is enabled for terminal sessions.

SUMMARY STEPS

  1. switch# terminal monitor
  2. switch# configure terminal
  3. switch(config)# logging console [severity-level]
  4. (Optional) switch(config)# no logging console [severity-level]
  5. switch(config)# logging monitor [severity-level]
  6. (Optional) switch(config)# no logging monitor [severity-level]
  7. (Optional) switch# show logging console
  8. (Optional) switch# show logging monitor
  9. (Optional) switch# copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# terminal monitor

Copies syslog messages from the console to the current terminal session.

Step 2

switch# configure terminal

Enters global configuration mode.

Step 3

switch(config)# logging console [severity-level]

Enables the switch to log messages to the console session based on a specified severity level or higher (a lower number value indicates a higher severity level). Severity levels range from 0 to 7:

  • 0 – emergency

  • 1 – alert

  • 2 – critical

  • 3 – error

  • 4 – warning

  • 5 – notification

  • 6 – informational

  • 7 – debugging

If the severity level is not specified, the default of 2 is used.

Step 4

(Optional) switch(config)# no logging console [severity-level]

(Optional)

Disables logging messages to the console.

Step 5

switch(config)# logging monitor [severity-level]

Enables the switch to log messages to the monitor based on a specified severity level or higher (a lower number value indicates a higher severity level). Severity levels range from 0 to 7:

  • 0 – emergency

  • 1 – alert

  • 2 – critical

  • 3 – error

  • 4 – warning

  • 5 – notification

  • 6 – informational

  • 7 – debugging

If the severity level is not specified, the default of 2 is used.

The configuration applies to Telnet and SSH sessions.

Step 6

(Optional) switch(config)# no logging monitor [severity-level]

(Optional)

Disables logging messages to Telnet and SSH sessions.

Step 7

(Optional) switch# show logging console

(Optional)

Displays the console logging configuration.

Step 8

(Optional) switch# show logging monitor

(Optional)

Displays the monitor logging configuration.

Step 9

(Optional) switch# copy running-config startup-config

(Optional)

Copies the running configuration to the startup configuration.

Example

The following example shows how to configure a logging level of 3 for the console: 

switch# configure terminal

switch(config)# logging console 3

The following example shows how to display the console logging configuration: 

switch# show logging console

Logging console:                enabled (Severity: error)

The following example shows how to disable logging for the console: 

switch# configure terminal

switch(config)# no logging console

The following example shows how to configure a logging level of 4 for the terminal session: 

switch# terminal monitor

switch# configure terminal

switch(config)# logging monitor 4

The following example shows how to display the terminal session logging configuration: 

switch# show logging monitor

Logging monitor:                enabled (Severity: warning)

The following example shows how to disable logging for the terminal session: 

switch# configure terminal

switch(config)# no logging monitor

Configuring System Message Logging to a File

You can configure the switch to log system messages to a file. By default, system messages are logged to the file log:messages.

SUMMARY STEPS

  1. switch# configure terminal
  2. switch(config)# logging logfile logfile-name severity-level [size bytes]
  3. (Optional) switch(config)# no logging logfile [logfile-name severity-level [size bytes]]
  4. (Optional) switch# show logging info
  5. (Optional) switch# copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# logging logfile logfile-name severity-level [size bytes]

Configures the name of the log file used to store system messages and the minimum severity level to log. You can optionally specify a maximum file size. The default severity level is 5 and the file size is 4194304.

Severity levels range from 0 to 7:

  • 0 – emergency

  • 1 – alert

  • 2 – critical

  • 3 – error

  • 4 – warning

  • 5 – notification

  • 6 – informational

  • 7 – debugging

The file size is from 4096 to 10485760 bytes.

Step 3

(Optional) switch(config)# no logging logfile [logfile-name severity-level [size bytes]]

(Optional)

Disables logging to the log file. You can optionally specify a maximum file size. The default severity level is 5 and the file size is 4194304.

Step 4

(Optional) switch# show logging info

(Optional)

Displays the logging configuration. You can optionally specify a maximum file size. The default severity level is 5 and the file size is 4194304.

Step 5

(Optional) switch# copy running-config startup-config

(Optional)

Copies the running configuration to the startup configuration.

Example

The following example shows how to configure a switch to log system messages to a file: 

switch# configure terminal
switch(config)# logging logfile my_log 6 size 4194304

The following example shows how to display the logging configuration (some of the output has been removed for brevity): 

switch# show logging info
Logging console:                enabled (Severity: debugging)
Logging monitor:                enabled (Severity: debugging)
Logging timestamp:              Seconds
Logging server:                 disabled
Logging logfile:                enabled
        Name - my_log: Severity - informational Size - 4194304
Facility        Default Severity        Current Session Severity
--------        ----------------        ------------------------
aaa                     3                       3
afm                     3                       3
altos                   3                       3
auth                    0                       0
authpriv                3                       3
bootvar                 5                       5
callhome                2                       2
capability              2                       2
cdp                     2                       2
cert_enroll             2                       2
...

Configuring Module and Facility Messages Logging

You can configure the severity level and time-stamp units of messages logged by modules and facilities.

SUMMARY STEPS

  1. switch# configure terminal
  2. switch(config)# logging module [severity-level]
  3. switch(config)# logging level facility severity-level
  4. (Optional) switch(config)# no logging module [severity-level]
  5. (Optional) switch(config)# no logging level [facility severity-level]
  6. (Optional) switch# show logging module
  7. (Optional) switch# show logging level [facility]
  8. (Optional) switch# copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# logging module [severity-level]

Enables module log messages that have the specified severity level or higher. Severity levels range from 0 to 7:

  • 0 – emergency

  • 1 – alert

  • 2 – critical

  • 3 – error

  • 4 – warning

  • 5 – notification

  • 6 – informational

  • 7 – debugging

If the severity level is not specified, the default of 5 is used.

Step 3

switch(config)# logging level facility severity-level

Enables logging messages from the specified facility that have the specified severity level or higher. Severity levels from 0 to 7:

  • 0 – emergency

  • 1 – alert

  • 2 – critical

  • 3 – error

  • 4 – warning

  • 5 – notification

  • 6 – informational

  • 7 – debugging

To apply the same severity level to all facilities, use the all facility. For defaults, see the show logging level command.

Note

 

If the default severity and current session severity of a component is the same, then the logging level for the component will not be displayed in the running configuration.

Step 4

(Optional) switch(config)# no logging module [severity-level]

(Optional)

Disables module log messages.

Step 5

(Optional) switch(config)# no logging level [facility severity-level]

(Optional)

Resets the logging severity level for the specified facility to its default level. If you do not specify a facility and severity level, the switch resets all facilities to their default levels.

Step 6

(Optional) switch# show logging module

(Optional)

Displays the module logging configuration.

Step 7

(Optional) switch# show logging level [facility]

(Optional)

Displays the logging level configuration and the system default level by facility. If you do not specify a facility, the switch displays levels for all facilities.

Step 8

(Optional) switch# copy running-config startup-config

(Optional)

Copies the running configuration to the startup configuration.

Example

The following example shows how to configure the severity level of module and specific facility messages: 

switch# configure terminal

switch(config)# logging module 3

switch(config)# logging level aaa 2

Configuring Logging Timestamps

You can configure the time-stamp units of messages logged by the Cisco Nexus Series switch.

SUMMARY STEPS

  1. switch# configure terminal
  2. switch(config)# logging timestamp {microseconds | milliseconds | seconds}
  3. (Optional) switch(config)# no logging timestamp {microseconds | milliseconds | seconds}
  4. (Optional) switch# show logging timestamp
  5. (Optional) switch# copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# logging timestamp {microseconds | milliseconds | seconds}

Sets the logging time-stamp units. By default, the units are seconds.

Step 3

(Optional) switch(config)# no logging timestamp {microseconds | milliseconds | seconds}

(Optional)

Resets the logging time-stamp units to the default of seconds.

Step 4

(Optional) switch# show logging timestamp

(Optional)

Displays the logging time-stamp units configured.

Step 5

(Optional) switch# copy running-config startup-config

(Optional)

Copies the running configuration to the startup configuration.

Example

The following example shows how to configure the time-stamp units of messages: 

switch# configure terminal
switch(config)# logging timestamp milliseconds
switch(config)# exit
switch# show logging timestamp
Logging timestamp:              Milliseconds

Configuring Syslog Servers

You can configure up to eight syslog servers that reference remote systems where you want to log system messages.

SUMMARY STEPS

  1. configure terminal
  2. logging server host [severity-level [use-vrf vrf-name [facility facility]]]
  3. (Optional) no logging server host
  4. (Optional) show logging server
  5. (Optional) copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:

switch# configure terminal
switch(config)#

Enters global configuration mode.

Step 2

logging server host [severity-level [use-vrf vrf-name [facility facility]]]

Example:

switch(config)# logging server 172.28.254.254 5 
use-vrf default facility local3

Configures a host to receive syslog messages.

  • The host argument identifies the hostname or the IPv4 or IPv6 address of the syslog server host.

  • The severity-level argument limits the logging of messages to the syslog server to a specified level. Severity levels range from 0 to 7. See Table 1.

  • The use vrf vrf-name keyword identifies the default or management values for the VRF name. If a specific VRF is not identified, management is the default.

    The show running command output can display or not display the VRF based on the following configuration scenarios:

    • You have not configured any VRF and the system takes the management VRF as the default. Then this VRF is not displayed in the output.

    • You have configured management VRF. Then this VRF is not displayed in the output as the system identifies it as the default.

    • You have configured any other VRF. Then this VRF is displayed in the output.

    Note

     

    The current Cisco Fabric Services (CFS) distribution does not support VRF. If CFS distribution is enabled, the logging server configured with the default VRF is distributed as the management VRF.

  • The facility argument names the syslog facility type. The default outgoing facility is local7.

    The facilities are listed in the command reference for the Cisco Nexus Series software that you are using.

Note

 

Debugging is a CLI facility but the debug syslogs are not sent to the server.

Step 3

(Optional) no logging server host

Example:

switch(config)# no logging server 172.28.254.254 5
 (Optional)

Removes the logging server for the specified host.

Step 4

(Optional) show logging server

Example:

switch# show logging server
 (Optional)

Displays the syslog server configuration.

Step 5

(Optional) copy running-config startup-config

Example:

switch(config)# copy running-config startup-config
(Optional)

Saves the change persistently through reboots and restarts by copying the running configuration to the startup configuration.

Example

The following examples show how to configure a syslog server: 

switch# configure terminal
switch(config)# logging server 172.28.254.254 5 
use-vrf default facility local3

switch# configure terminal
switch(config)# logging server 172.28.254.254 5 use-vrf management facility local3

Configuring syslog on a UNIX or Linux System

You can configure a syslog server on a UNIX or Linux system by adding the following line to the /etc/syslog.conf file: 

facility.level <five tab characters> action

The following table describes the syslog fields that you can configure.

Table 3. syslog Fields in syslog.conf

Field

Description

Facility

Creator of the message, which can be auth, authpriv, cron, daemon, kern, lpr, mail, mark, news, syslog, user, local0 through local7, or an asterisk (*) for all. These facility designators allow you to control the destination of messages based on their origin.

Note

 

Check your configuration before using a local facility.

Level

Minimum severity level at which messages are logged, which can be debug, info, notice, warning, err, crit, alert, emerg, or an asterisk (*) for all. You can use none to disable a facility.

Action

Destination for messages, which can be a filename, a hostname preceded by the at sign (@), or a comma-separated list of users or an asterisk (*) for all logged-in users.

SUMMARY STEPS

  1. Log debug messages with the local7 facility in the file /var/log/myfile.log by adding the following line to the /etc/syslog.conf file:
  2. Create the log file by entering these commands at the shell prompt:
  3. Make sure that the system message logging daemon reads the new changes by checking myfile.log after entering this command:

DETAILED STEPS

Step 1

Log debug messages with the local7 facility in the file /var/log/myfile.log by adding the following line to the /etc/syslog.conf file: 

debug.local7             /var/log/myfile.log

Step 2

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

$ touch /var/log/myfile.log
$ chmod 666 /var/log/myfile.log

Step 3

Make sure that the system message logging daemon reads the new changes by checking myfile.log after entering this command: 

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

Configuring syslog Server Configuration Distribution

You can distribute the syslog server configuration to other switches in the network by using the Cisco Fabric Services (CFS) infrastructure.

After you enable syslog server configuration distribution, you can modify the syslog server configuration and view the pending changes before committing the configuration for distribution. As long as distribution is enabled, the switch maintains pending changes to the syslog server configuration.


Note

If the switch is restarted, the syslog server configuration changes that are kept in volatile memory might get lost.

Before you begin

You must have configured one or more syslog servers.

SUMMARY STEPS

  1. switch# configure terminal
  2. switch(config)# logging distribute
  3. switch(config)# logging commit
  4. switch(config)# logging abort
  5. (Optional) switch(config)# no logging distribute
  6. (Optional) switch# show logging pending
  7. (Optional) switch# show logging pending-diff
  8. (Optional) switch# copy running-config startup-config

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# logging distribute

Enables distribution of the syslog server configuration to network switches using the CFS infrastructure. By default, distribution is disabled.

Step 3

switch(config)# logging commit

Commits the pending changes to the syslog server configuration for distribution to the switches in the fabric.

Step 4

switch(config)# logging abort

Cancels the pending changes to the syslog server configuration.

Step 5

(Optional) switch(config)# no logging distribute

(Optional)

Disables the distribution of the syslog server configuration to network switches using the CFS infrastructure. You cannot disable distribution when configuration changes are pending. See the logging commit and logging abort commands. By default, distribution is disabled.

Step 6

(Optional) switch# show logging pending

(Optional)

Displays the pending changes to the syslog server configuration.

Step 7

(Optional) switch# show logging pending-diff

(Optional)

Displays the differences from the current syslog server configuration to the pending changes of the syslog server configuration.

Step 8

(Optional) switch# copy running-config startup-config

(Optional)

Copies the running configuration to the startup configuration.

Displaying and Clearing Log Files

You can display or clear messages in the log file and the NVRAM.

SUMMARY STEPS

  1. switch# show logging last number-lines
  2. switch# show logging logfile [start-time yyyy mmm dd hh:mm:ss] [end-time yyyy mmm dd hh:mm:ss]
  3. switch# show logging nvram [last number-lines]
  4. switch# clear logging logfile
  5. switch# clear logging nvram

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# show logging last number-lines

Displays the last number of lines in the logging file. You can specify from 1 to 9999 for the last number of lines.

Step 2

switch# show logging logfile [start-time yyyy mmm dd hh:mm:ss] [end-time yyyy mmm dd hh:mm:ss]

Displays the messages in the log file that have a time stamp within the span entered. If you do not enter an end time, the current time is used. You enter three characters for the month time field and digits for the year and day time fields.

Step 3

switch# show logging nvram [last number-lines]

Displays the messages in the NVRAM. To limit the number of lines displayed, you can enter the last number of lines to display. You can specify from 1 to 100 for the last number of lines.

Step 4

switch# clear logging logfile

Clears the contents of the log file.

Step 5

switch# clear logging nvram

Clears the logged messages in NVRAM.

Example

The following example shows how to display messages in a log file: 

switch# show logging last 40

switch# show logging logfile start-time 2007 nov 1 15:10:0

switch# show logging nvram last 10

The following example shows how to clear messages in a log file: 

switch# clear logging logfile

switch# clear logging nvram

Configuring DOM Logging

Enabling DOM Logging

SUMMARY STEPS

  1. switch# configure terminal
  2. switch(config)# system ethernet dom polling

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# system ethernet dom polling

Enables transceiver digital optical monitoring periodic polling.

Example

The following example shows how to enable DOM logging.

switch# configure terminal
switch(config)# system ethernet dom polling

Disabling DOM Logging

SUMMARY STEPS

  1. switch# configure terminal
  2. switch(config)# no system ethernet dom polling

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# configure terminal

Enters global configuration mode.

Step 2

switch(config)# no system ethernet dom polling

Disables transceiver digital optical monitoring periodic polling.

Example

The following example shows how to disable DOM logging.

switch# configure terminal
switch(config)# no system ethernet dom polling

Verifying the DOM Logging Configuration

Command

Purpose

show system ethernet dom polling status

Displays the transceiver digital optical monitoring periodic polling status.

Verifying the System Message Logging Configuration

Use these commands to verify system message logging configuration information:

Command

Purpose

show logging console

Displays the console logging configuration.

show logging info

Displays the logging configuration.

show logging ip access-list cache

Displays the IP access list cache.

show logging ip access-list cache detail

Displays detailed information about the IP access list cache.

show logging ip access-list status

Displays the status of the IP access list cache.

show logging last number-lines

Displays the last number of lines of the log file.

show logging level [facility]

Displays the facility logging severity level configuration.

show logging logfile [start-time yyyy mmm dd hh:mm:ss] [end-time yyyy mmm dd hh:mm:ss]

Displays the messages in the log file.

show logging module

Displays the module logging configuration.

show logging monitor

Displays the monitor logging configuration.

show logging nvram [last number-lines]

Displays the messages in the NVRAM log.

show logging pending

Displays the syslog server pending distribution configuration.

show logging pending-diff

Displays the syslog server pending distribution configuration differences.

show logging server

Displays the syslog server configuration.

show logging session

Displays the logging session status.

show logging status

Displays the logging status.

show logging timestamp

Displays the logging time-stamp units configuration.

Repeated System Logging Messages

System processes generate logging messages. Depending on the filters used to control which severity levels are generated, a large number of messages can be produced with many of them being repeated.

To make it easier to develop scripts to manage the volume of logging messages, and to eliminate repeated messages from “flooding” the output of the show logging log command, the following method of logging repeated messages is used.

In the old method, when the same message was repeated, the default was to state the number of times it reoccurred in the message:

2019 Mar 11 13:42:44 Cisco-customer %PTP-2-PTP_INCORRECT_PACKET_ON_SLAVE: 
Incorrect delay response packet received on slave interface Eth1/48 by 
2c:5a:0f:ff:fe:51:e9:9f. Source Port Identity is 08:00:11:ff:fe:22:3e:4e. Requesting Port 
Identity is 00:1c:73:ff:ff:ee:f6:e5
2019 Mar 11 13:43:15 Cisco-customer last message repeated 242 times

The new method simply appends the repeat count to the end of the repeated message:

2019 Mar 11 13:42:44 Cisco-customer %PTP-2-PTP_INCORRECT_PACKET_ON_SLAVE: 
Incorrect delay response packet received on slave interface Eth1/48 by 
2c:5a:0f:ff:fe:51:e9:9f. Source Port Identity is 08:00:11:ff:fe:22:3e:4e. Requesting Port 
Identity is 00:1c:73:ff:ff:ee:f6:e5

2019 Mar 11 13:43:15 Cisco-customer %PTP-2-PTP_INCORRECT_PACKET_ON_SLAVE: 
Incorrect delay response packet received on slave interface Eth1/48 by 
2c:5a:0f:ff:fe:51:e9:9f. Source Port Identity is 08:00:11:ff:fe:22:3e:4e. Requesting Port 
Identity is 00:1c:73:ff:ff:ee:f6:e5 (message repeated 242 times)