- Catalyst 3750-X and 3560-X Switch Software Configuration Guide, Cisco IOS 15.0(2)SE and Later
- Table of Contents
- Preface
- Overview
- Using the Command-Line Interface
- Configuring Cisco IOS Configuration Engine
- Assigning the Switch IP Address and Default Gateway
- Managing Switch Stacks
- Clustering Switches
- Administering the Switch
- Configuring SDM Templates
- Managing Catalyst 3750-X Stack Power
- Configuring Switch-Based Authentication
- Configuring IEEE 802.1x Port-Based Authentication
- Configuring MACsec Encryption
- Configuring Web-Based Authentication
- Configuring Cisco TrustSec
- Configuring Interface Characteristics
- Configuring VLANs
- Configuring VTP
- Configuring Voice VLANs
- Configuring Private VLANs
- Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
- Configuring STP
- Configuring MSTP
- Configuring Optional Spanning-Tree Features
- Configuring Resilient Ethernet Protocol
- Configuring Flex Links
- Configuring DHCP Features and IP Source Guard
- Configuring Dynamic ARP Inspection
- Configuring IGMP Snooping and MVR
- Configuring IPv6 MLD Snooping
- Configuring CDP
- Configuring Port-Based Traffic Control
- Configuring LLDP, LLDP-MED, and Wired Location Service
- Configuring UDLD
- Configuring SPAN and RSPAN
- Configuring RMON
- Configuring System Message Logging and Smart Logging
- Configuring SNMP
- Configuring Embedded Event Manager
- Configuring Network Security with ACLs
- Configuring QoS
- Configuring IPv6 ACLs
- Configuring EtherChannels and Link-State Tracking
- Configuring TelePresence E911 IP Phone Support
- Configuring IP Unicast Routing
- Configuring IPv6 Unicast Routing
- Configuring HSRP and VRRP
- Configuring Cisco IOS IP SLAs Operations
- Configuring Flexible NetFlow
- Configuring Enhanced Object Tracking
- Configuring WCCP
- Configuring IP Multicast Routing
- Implementing IPv6 Multicast
- Configuring MSDP
- Configuring Fallback Bridging
- Troubleshooting
- Configuring Online Diagnostics
- Working with the Cisco IOS File System, Configuration Files, and Software Images
- Unsupported Commands in Cisco IOS Release 15.0(2)SE
- Index
Catalyst 3750-X and Catalyst 3560-X Switch Software Configuration Guide, Cisco IOS Release 15.0(2)SE and Later
Bias-Free Language
The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
- Updated:
- September 24, 2014
Chapter: Configuring System Message Logging and Smart Logging
- Understanding System Message Logging
- Configuring System Message Logging
- System Log Message Format
- Default System Message Logging Configuration
- Disabling Message Logging
- Setting the Message Display Destination Device
- Synchronizing Log Messages
- Enabling and Disabling Time Stamps on Log Messages
- Enabling and Disabling Sequence Numbers in Log Messages
- Defining the Message Severity Level
- Limiting Syslog Messages Sent to the History Table and to SNMP
- Enabling the Configuration-Change Logger
- Configuring UNIX Syslog Servers
Configuring System Message Logging and Smart Logging
This chapter describes how to configure system message logging on the Catalyst 3750-X or 3560-X switch. The switch also supports Smart Logging to capture packet flows based on configured triggers.
Note For complete syntax and usage information for the commands used in this chapter, see the Cisco IOS Configuration Fundamentals Command Reference, Release 12.4 and the command reference for this release.
- Understanding System Message Logging
- Configuring System Message Logging
- Configuring Smart Logging
- Displaying the Logging Configuration
Understanding System Message Logging
By default, a switch sends the output from system messages and debug privileged EXEC commands to a logging process. Stack members can trigger system messages. A stack member that generates a system message appends its hostname in the form of hostname-n , where n is a switch number from 1 to 9, and redirects the output to the logging process on the stack master. Though the stack master is a stack member, it does not append its hostname to system messages. 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. On Catalyst 3750-X switches, messages appear on the active consoles after the process that generated them has finished. On Catalyst 3560-X switches, 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. 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, and in the case of a switch stack, on the stack master. If a standalone switch or the stack master fails, 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. In a switch stack, all stack member consoles provide the same console output.
Configuring System Message Logging
- System Log Message Format
- Default System Message Logging Configuration
- Disabling Message Logging (optional)
- Setting the Message Display Destination Device (optional)
- Synchronizing Log Messages (optional)
- Enabling and Disabling Time Stamps on Log Messages (optional)
- Enabling and Disabling Sequence Numbers in Log Messages (optional)
- Defining the Message Severity Level (optional)
- Limiting Syslog Messages Sent to the History Table and to SNMP (optional)
- Enabling the Configuration-Change Logger (optional)
- Configuring UNIX Syslog Servers (optional)
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:
For Catalyst 3750-X switches, seq no:timestamp: %facility-severity-MNEMONIC:description (hostname-n)
For Catalyst 3560-X switches, 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.
Stamps log messages with a sequence number only if the service sequence-numbers global configuration command is configured. For more information, see the “Enabling and Disabling Sequence Numbers in Log Messages” section. |
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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 the “Enabling and Disabling Time Stamps on Log Messages” section. |
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The facility to which the message refers (for example, SNMP, SYS, and so forth). For a list of supported facilities, see Table 1-4. |
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Single-digit code from 0 to 7 that is the severity of the message. For a description of the severity levels, see Table 1-3. |
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Text string containing detailed information about the event being reported. |
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Hostname of a stack member and its switch number in the stack. Though the stack master is a stack member, it does not append its hostname to system messages. |
This example shows a partial switch system message for a stack master and a stack member (hostname Switch-2 ):
00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/1, changed state to down 2
00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/1, changed state to down 2 (Switch-2)
This example shows a partial switch system message on a Catalyst 3560-X switch:
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.
Beginning in privileged EXEC mode, follow these steps to disable message logging. This procedure is optional.
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 . For more information, see the “Synchronizing Log Messages” section.
To re-enable 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. Beginning in privileged EXEC mode, use one or more of the following commands to specify the locations that receive messages. This procedure is optional.
Log messages to an internal buffer on the switch or on a standalone switch or, in the case of a switch stack, on the stack master. The range is 4096 to 2147483647 bytes. The default buffer size is 4096 bytes. If a standalone switch or the stack master 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. |
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Log messages to a UNIX syslog server host. For host , specify 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. For complete syslog server configuration steps, see the “Configuring UNIX Syslog Servers” section. |
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logging file flash: filename [ max-file-size [ min-file-size ]] [ severity-level-number | type ] |
Store log messages in a file in flash memory on a standalone switch or, in the case of a switch stack, on the stack master.
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Log 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. |
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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.
Use the logging event power-inline-status interface configuration command to enable and to disable logging of Power over Ethernet (PoE) events on specific PoE-capable ports. Logging on these ports is enabled by default.
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 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.
Beginning in privileged EXEC mode, follow these steps to configure synchronous logging. This procedure is optional.
To disable synchronization of unsolicited messages and debug output, use the no logging synchronous [l evel severity-level | all ] [ limit number-of-buffers ] line configuration command.
Enabling and Disabling Time Stamps on Log Messages
By default, log messages are not time-stamped.
Beginning in privileged EXEC mode, follow these steps to enable time-stamping of log messages. This procedure is optional.
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 s ervice timestamps log uptime global configuration command enabled:
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.
Beginning in privileged EXEC mode, follow these steps to enable sequence numbers in log messages. This procedure 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
You can limit messages displayed to the selected device by specifying the severity level of the message, which are described in Table 1-3 .
Beginning in privileged EXEC mode, follow these steps to define the message severity level. This procedure is optional.
Limit messages logged to the console. By default, the console receives debugging messages and numerically lower levels (see Table 1-3). |
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Limit messages logged to the terminal lines. By default, the terminal receives debugging messages and numerically lower levels (see Table 1-3). |
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Limit messages logged to the syslog servers. By default, syslog servers receive informational messages and numerically lower levels (see Table 1-3). For complete syslog server configuration steps, see the “Configuring UNIX Syslog Servers” section. |
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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 1-3 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
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 1-3) are stored in the history table even if syslog traps are not enabled.
Beginning in privileged EXEC mode, follow these steps to change the level and history table size defaults. This procedure is optional.
logging history level1 |
Change the default level of syslog messages stored in the history file and sent to the SNMP server. See Table 1-3 for a list of level keywords. By default, warnings , errors , critical , alerts , and emergencies messages are sent. |
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Specify 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. |
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1.Table 1-3 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. |
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.
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). You can clear the log at any time by entering the no logging enable command followed by the logging enable command to disable and re-enable logging.
Use the show archive log config { all | number [ end-number ] | user username [ session number ] number [ end-number ] | statistics } [ provisioning ] privileged EXEC command to display the complete configuration log or the log for specified parameters.
The default is that configuration logging is disabled.
For information about the commands, see the Cisco IOS Configuration Fundamentals and Network Management Command Reference, Release 12.3 T .
Beginning in privileged EXEC mode, follow these steps to enable configuration logging:
This example shows how to enable the configuration-change logger and to set the number of entries in the log to 500.
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.
Log in as root, and perform these steps:
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.
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 1-4 for information on the facilities. The debug keyword specifies the syslog level; see Table 1-3 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 Make sure 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.
Beginning in privileged EXEC mode, follow these steps to configure UNIX system facility message logging. This procedure is optional.
Log 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. |
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Limit messages logged to the syslog servers. Be default, syslog servers receive informational messages and lower. See Table 1-3 for level keywords. |
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Configure the syslog facility. See Table 1-4 for facility-type keywords. |
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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 1-4 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.
Configuring Smart Logging
Smart logging provides a mechanism to capture and export packet flows based on predefined or user-configured triggers. Beginning with Cisco IOS Release 12.2(58)SE, 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 Cisco Flexible NetFlow, see the
Cisco IOS Flexible NetFlow Configuration Guide, Release 12.4T
:
http://www.cisco.com.do/en/US/docs/ios/fnetflow/configuration/guide/12_4t/fnf_12_4t_book.html
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.
Enabling Smart Logging
Beginning in privileged EXEC mode, follow these steps to globally enable smart logging:
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. Beginning in privileged EXEC mode, follow these steps to enable DHCP snooping smart logging:
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 NetFlow collector.
Beginning in privileged EXEC mode, follow these steps to enable dynamic ARP inspection smart logging:
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.
Beginning in privileged EXEC mode, follow these steps to enable IP source guard smart logging:
Enabling 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.
You add the smart log configuration option when you create the permit and deny conditions for an ACL. This example enables smart logging on a numbered access list:
Displaying the Logging Configuration
To display the logging configuration and the contents of the log buffer, use the show logging privileged EXEC command. For information about the fields in this display, see the Cisco IOS Configuration Fundamentals Command Reference, Release 12.4 on Cisco.com.
To display smart logging information, use the show logging smartlog command. For information about this command, see the command reference for this release.
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