Configuring System Message Logging and Smart Logging

Information About Configuring System Message Logs and Smart Logs

System Messsage 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.

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 active consoles 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. For information on possible messages, see the system message guide for this release.

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 on a standalone switch. If a standalone switch , the log is lost unless you had saved it to flash memory.

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


Note

The syslog format is compatible with 4.3 BSD UNIX.

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. Depending on the switch, messages appear in one of these formats:

  • seq no:timestamp: %facility-severity-MNEMONIC:description (hostname-n)

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

The part of the message preceding the percent sign depends on the setting of these global configuration commands:

  • service sequence-numbers

  • service timestamps log datetime

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

  • service timestamps log uptime

Table 1. 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.

timestamp formats:

mm/dd h h: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.

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.

Default System Message Logging Settings

Table 2. Default System Message Logging Settings

Feature

Default Setting

System message logging to the console

Enabled.

Console severity

Debugging.

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.

Server facility

Local7

Server severity

Informational.

Syslog Message Limits

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.

The history table lists the level keywords and severity level. For SNMP usage, the severity level values increase by 1. For example, emergencies equal 1, not 0, and critical equals 3, not 2.

Smart Logging

Smart logging provides a mechanism to capture and export packet flows based on predefined or user-configured triggers. The switch supports smart logging for these events:

  • DHCP snooping violations

  • Dynamic ARP inspection violations

  • IP source guard denied traffic

  • ACL permitted or denied traffic

To use smart logging, you must first configure a NetFlow exporter that you identify when you enable smart logging. For information on configuring the NetFlow feature, see the Catalyst 2960-XR Switch NetFlow Lite Configuration Guide.

Smart logging processing creates a NetFlow packet for the configured event and sends the packet to the external NetFlow collector. Smart logging counters reflect the number of packets that are logged. This number is the same as the number of packets sent to the collector if no packets are dropped between the switch and the NetFlow collector. You enable smart logging globally on the switch, and you can then configure specific events to be smart logged.

Smart Logging for Port ACL Deny or Permit Actions

The switch supports port ACLs, router ACLs, and VLAN ACLs.

  • Port ACLs are IP or MAC ACLs applied to a Layer 2 port. Logging is not supported on port ACLs, but smart logging is supported on IP ACLs applied to Layer 2 ports.

  • Router ACLs are ACLs applied to Layer 3 ports. Router ACLs support logging but not smart logging.

  • VLAN ACLs or VLAN maps are ACLs applied to VLANs. You can configure logging on VLAN maps, but not smart logging.

When you configure any permit or deny ACL, you can configure logging or smart logging as part of the access list, to take place on all traffic that the ACL permits or denies. The type of port that you attach the ACL to determines the type of logging. If you attach an ACL with smart log configured to a router or a VLAN, the ACL is attached, but smart logging does not take affect. If you configure logging on an ACL attached to a Layer 2 port, the logging keyword is ignored.

How to Configure System Message Logs and Smart Logs

Setting the Message Display Destination Device

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

This task is optional.

SUMMARY STEPS

  1. configure terminal
  2. logging buffered [size]
  3. logging host
  4. logging file flash: filename [max-file-size [min-file-size]] [severity-level-number | type]
  5. end
  6. terminal monitor

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

logging buffered [size]

Example:


Device(config)# logging buffered 8192

Logs messages to an internal buffer on the switch or on a standalone switch or, in the case of a switch stack, on the active switch. The range is 4096 to 2147483647 bytes. The default buffer size is 4096 bytes.

If a standalone switch or the active switch fails, the log file is lost unless you 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.

Step 3

logging host

Example:


Device(config)# logging 125.1.1.100

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.
Step 4

logging file flash: filename [max-file-size [min-file-size]] [severity-level-number | type]

Example:


Device(config)# logging file flash:log_msg.txt 40960 4096 3

Stores log messages in a file in flash memory on a standalone switch or, in the case of a switch stack, on the active switch.

  • 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.

Step 5

end

Example:


Device(config)# end

Returns to privileged EXEC mode.
Step 6

terminal monitor

Example:


Device# 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

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.

This task is optional.

SUMMARY STEPS

  1. configure terminal
  2. line [console | vty] line-number [ending-line-number]
  3. logging synchronous [level [severity-level | all] | limit number-of-buffers]
  4. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

line [console | vty] line-number [ending-line-number]

Example:


Device(config)# line console

Specifies the line to be configured for synchronous logging of messages.

  • console — Specifies configurations that occur through the switch console port or the Ethernet management port.

  • line vty line-number — Specifies 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

You can also 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.
Step 3

logging synchronous [level [severity-level | all] | limit number-of-buffers]

Example:


Device(config)# logging synchronous level 3 limit 1000

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.

Step 4

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

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.

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.

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

This task is optional.

SUMMARY STEPS

  1. configure terminal
  2. no logging console
  3. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

no logging console

Example:


Device(config)# no logging console

Disables message logging.
Step 3

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Enabling and Disabling Time Stamps on Log Messages

By default, log messages are not time-stamped.

This task is optional.

SUMMARY STEPS

  1. configure terminal
  2. Use one of these commands:
    • service timestamps log uptime
    • service timestamps log datetime[msec | localtime | show-timezone]
  3. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

Use one of these commands:

  • service timestamps log uptime
  • service timestamps log datetime[msec | localtime | show-timezone]

Example:

Device(config)# service timestamps log uptime

or

Device(config)# service timestamps log datetime

Enables log time stamps.

  • log uptime — Enables time stamps on log messages, showing the time since the system was rebooted.

  • log datetime — 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.

Step 3

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Enabling and Disabling Sequence Numbers in Log Messages

If there is more than one log message with the same time stamp, you can display messages with sequence numbers to view these messages. By default, sequence numbers in log messages are not displayed.

This task is optional.

SUMMARY STEPS

  1. configure terminal
  2. service sequence-numbers
  3. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

service sequence-numbers

Example:


Device(config)# service sequence-numbers

Enables sequence numbers.
Step 3

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Defining the Message Severity Level

Limit messages displayed to the selected device by specifying the severity level of the message.

This task is optional.

SUMMARY STEPS

  1. configure terminal
  2. logging console level
  3. logging monitor level
  4. logging trap level
  5. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

logging console level

Example:


Device(config)# logging console 3

Limits messages logged to the console.

By default, the console receives debugging messages and numerically lower levels.
Step 3

logging monitor level

Example:


Device(config)# logging monitor 3

Limits messages logged to the terminal lines.

By default, the terminal receives debugging messages and numerically lower levels.
Step 4

logging trap level

Example:


Device(config)# logging trap 3

Limits messages logged to the syslog servers.

By default, syslog servers receive informational messages and numerically lower levels.
Step 5

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Limiting Syslog Messages Sent to the History Table and to SNMP

This task explains how to limit syslog messages that are sent to the history table and to SNMP.

This task is optional.

SUMMARY STEPS

  1. configure terminal
  2. logging history level
  3. logging history size number
  4. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

logging history level

Example:


Device(config)# logging history 3

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.

Step 3

logging history size number

Example:


Device(config)# logging history size 200

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.
Step 4

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Logging Messages to a UNIX Syslog Daemon

This task 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.

Before you begin

  • Log in as root.

  • Before you can send system log messages to a UNIX syslog server, you must configure the syslog daemon on a UNIX server.

SUMMARY STEPS

  1. Add a line to the file /etc/syslog.conf.
  2. Enter these commands at the UNIX shell prompt.
  3. Make sure the syslog daemon reads the new changes.

DETAILED STEPS

  Command or Action Purpose
Step 1

Add a line to the file /etc/syslog.conf.

Example:


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

  • local7 — Specifies the logging facility.

  • debug — Specifies the syslog level. The file must already exist, and the syslog daemon must have permission to write to it.

Step 2

Enter these commands at the UNIX shell prompt.

Example:


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

Creates the log file. The syslog daemon sends messages at this level or at a more severe level to this file.

Step 3

Make sure the syslog daemon reads the new changes.

Example:


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

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

Enabling Smart Logging

SUMMARY STEPS

  1. configure terminal
  2. logging smartlog
  3. logging smartlog exporter exporter_name
  4. logging packet capture size packet_size
  5. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

logging smartlog

Example:


Device(config)#logging smartlog

Turns on the smart logging feature.
Step 3

logging smartlog exporter exporter_name

Example:


Device(config)# logging smartlog exporter export-file

Identifies the smart log exporter. You must have already configured the exporter by using the NetFlow CLI. If the exporter name does not exist, you receive an error message. By default, the switch sends data to the collector every 60 seconds.

Step 4

logging packet capture size packet_size

Example:


Device(config)# logging packet capture size 128
(Optional) Configures the size of the packet to be sent to the exporter. The range is from 64 to 1024 bytes in 4-byte increments. The default size is 64 bytes.
Note 

Increasing the packet capture size reduces the number of flow records per packet.

Step 5

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Enabling Smart Logging for DHCP Snooping Violations

DHCP snooping intercepts and inspects DHCP packets entering untrusted ports and either forwards or drops the packets. You can enable DHCP snooping smart logging to send the contents of dropped packets to the NetFlow collector.

SUMMARY STEPS

  1. configure terminal
  2. ip dhcp snooping vlan {vlan-id | vlan-range }smartlog
  3. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

ip dhcp snooping vlan {vlan-id | vlan-range }smartlog

Example:


Device(config)#ip dhcp snooping vlan 5-8 smartlog

Specifies a VLAN ID or a range of VLANs on which to enable DHCP snooping smart logging.
Step 3

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Enabling Smart Logging for Dynamic ARP Inspection Violations

Dynamic ARP inspection intercepts ARP packets on untrusted ports and validates them before forwarding. The functionality is similar to DHCP snooping but for ARP packets. You can configure dynamic ARP inspection logging by using the ip arp inspection log-buffer global configuration command. By default, all dropped packets are logged. You can also configure the switch to apply smart logging to the same packets that are being logged, sending the packet contents packet to the Cisco NetFlow collector.

SUMMARY STEPS

  1. configure terminal
  2. ip arp inspection smartlog
  3. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

ip arp inspection smartlog

Example:

Device(config)# ip arp inspection smartlog

Specifies that whatever packets are currently being logged (the default is all dropped packets) are also smart-logged.
Step 3

end

Example:


Device(config)# end

Returns to privileged EXEC mode.

Enabling Smart Logging for IP Source Guard Violations

IP source guard is a security feature related to DHCP snooping. You can use IP source guard to filter traffic based on the IP source address or the MAC address. All IP packets with a source address other than the specified address or addresses learned through DHCP snooping are denied. You can enable IP source guard smart logging to send the contents of the denied packets to the NetFlow collector.

SUMMARY STEPS

  1. configure terminal
  2. interface interface-id
  3. ip verify source smartlog
  4. end

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.
Step 2

interface interface-id

Example:


Device(config)#interface GigabitEthernet1/0/1

Specifies an interface and enters interface configuration mode.
Step 3

ip verify source smartlog

Example:


Device(config-if)# ip verify source smartlog

Enables IP source guard smart logging for all packets that are denied by IP source guard.
Step 4

end

Example:


Device(config-if)# end

Returns to privileged EXEC mode.

Monitoring and Maintaining System Message Logs and Smart Logs

Monitoring Configuration Archive Logs

Command

Purpose

show archive log config {all | number [end-number] | user username [session number] number [end-number] | statistics} [provisioning]

Displays the entire configuration log or the log for specified parameters.

Monitoring Smart Logging

Command

Purpose

show logging smartlog

Displays smart logging entries.

show ip arp inspection

Displays the IP ARP smart logging entries.

show ip verify source

Displays IP source guard smart logging entries. The output shows whether or not smart logging is enabled on the interface.

Configuration Examples for System Message Logs and Smart Logs

Example: Stacking System Message

This example shows a partial switch system message for active stack and a stack member (hostname Switch-2): 


00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to up
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/2, 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 GigabitEthernet1/0/1, 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) 

00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up (Switch-2)
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/1, changed state to up (Switch-2)
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/2, changed state to up (Switch-2)
00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down (Switch-2)
00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/1, changed state to down 2 (Switch-2)

Example: Switch System Message

This example shows a partial switch system message on a switch:


00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet0/2, 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 GigabitEthernet0/1, 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)

Example: Enabling Smart Logging

You add the smart log configuration option when you create the permit and deny conditions for an ACL.

This example shows how to enable smart logging on a numbered access list:


Device(config)#  access-list 199 permit ip any any smartlog

This example shows how to enable smart logging on a named access list:


Device(config)#  ip access-list extended test1
Device(config-ext-nacl)# deny ip host 10.1.1.3 any smartlog

Examples: Displaying Service Timestamps Log

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) 
(Switch-2)
This example shows part of a logging display with the service timestamps log uptime global configuration command enabled: 

 
00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up (Switch-2)
This example shows part of a logging display with the sequence numbers enabled.

 
000019: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36) (Switch-2)

Additional References for System Message Logs and Smart Logs

Related Documents

Related Topic Document Title

System message log commands

Catalyst 2960-XR Switch System Management Command Reference

Platform-independent command references

 Cisco IOS 15.3M&T Command References

Platform-independent configuration information

 Cisco IOS 15.3M&T Configuration Guides

Standards and RFCs

Standard/RFC Title
None

—

MIBs

MIB MIBs Link

All supported MIBs for this release.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

Technical Assistance

Description Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/support

Feature History and Information For System Message Logs

Release

Modification

Cisco IOS Release 15.0(2)EX1

This feature was introduced.