Cisco ASA 5500 Series Configuration Guide using the CLI, 8.2
Configuring Logging
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Configuring Logging

Table Of Contents

Configuring Logging

Information About Logging

Logging in Multiple Context Mode

Analyzing Syslog Messages

Syslog Message Format

Severity Levels

Message Classes and Range of Syslog IDs

Filtering Syslog Messages

Using Custom Message Lists

Licensing Requirements for Logging

Prerequisites for Logging

Guidelines and Limitations

Configuring Logging

Enabling Logging

Sending Syslog Messages to an SNMP Server

Sending Syslog Messages to a Syslog Server

Sending Syslog Messages to the Console Port

Sending Syslog Messages to an E-mail Address

Sending Syslog Messages to ASDM

Sending Syslog Messages to a Telnet or SSH Session

Sending Syslog Messages to the Internal Log Buffer

Sending All Syslog Messages in a Class to a Specified Output Destination

Creating a Custom Message List

Enabling Secure Logging

Configuring the Logging Queue

Including the Device ID in Syslog Messages

Generating Syslog Messages in EMBLEM Format

Including the Date and Time in Syslog Messages

Disabling a Syslog Message

Changing the Severity Level of a Syslog Message

Limiting the Rate of Syslog Message Generation

Changing the Amount of Internal Flash Memory Available for Logs

Monitoring Logging

Configuration Examples for Logging

Feature History for Logging


Configuring Logging


This chapter describes how to configure and manage logs for the ASA, and includes the following sections:

Information About Logging

Licensing Requirements for Logging

Prerequisites for Logging

Guidelines and Limitations

Configuring Logging

Monitoring Logging

Configuration Examples for Logging

Feature History for Logging

Information About Logging

The ASA system logs provide you with information for monitoring and troubleshooting the ASA. With the logging feature, you can do the following:

Specify which syslog messages should be logged.

Disable or change the severity level of a syslog message.

Specify one or more locations where syslog messages should be sent, including an internal buffer, one or more syslog servers, ASDM, an SNMP management station, specified e-mail addresses, or to Telnet and SSH sessions.

Configure and manage syslog messages in groups, such as by severity level or class of message.

Specify whether a rate-limit is applied to syslog generation.

Specify what happens to the contents of the internal buffer when the buffer becomes full: overwrite the buffer, send the buffer contents to an FTP server, or save the contents to internal flash memory.

Filter syslog messages by locations, by the severity of the syslog message, the class of the syslog message, or by creating a custom syslog message list.

This section includes the following topics:

Logging in Multiple Context Mode

Analyzing Syslog Messages

Syslog Message Format

Severity Levels

Filtering Syslog Messages

Message Classes and Range of Syslog IDs

Logging in Multiple Context Mode

Each security context includes its own logging configuration and generates its own messages. If you log in to the system or admin context, and then change to another context, messages you view in your session are only those that are related to the current context.

Syslog messages that are generated in the system execution space, including failover messages, are viewed in the admin context along with messages generated in the admin context. You cannot configure logging or view any logging information in the system execution space.

You can configure the ASA to include the context name with each message, which helps you differentiate context messages that are sent to a single syslog server. This feature also helps you to determine which messages are from the admin context and which are from the system; messages that originate in the system execution space use a device ID of system, and messages that originate in the admin context use the name of the admin context as the device ID.

Analyzing Syslog Messages

The following are some examples of the type of information you can obtain from a review of various syslog messages:

Connections that are allowed by ASA security policies. These messages help you spot "holes" that remain open in your security policies.

Connections that are denied by ASA security policies. These messages show what types of activity are being directed toward your secured inside network.

Using the ACE deny rate logging feature shows attacks that are occurring against your ASA.

IDS activity messages can show attacks that have occurred.

User authentication and command usage provide an audit trail of security policy changes.

Bandwidth usage messages show each connection that was built and torn down, as well as the duration and traffic volume used.

Protocol usage messages show the protocols and port numbers used for each connection.

Address translation audit trail messages record NAT or PAT connections being built or torn down, which are useful if you receive a report of malicious activity coming from inside your network to the outside world.

For more information about analyzing syslog messages, see Appendix E, "Configuring the Adaptive Security Appliance for Use with MARS."

Syslog Message Format

Syslog messages begin with a percent sign (%) and are structured as follows:

%ASA Level Message_number: Message_text
 
   

Field descriptions are as follows:

ASA

The syslog message facility code for messages that are generated by the ASA. This value is always ASA.

Level

1 through 7. The level reflects the severity of the condition described by the syslog message—the lower the number, the more severe the condition. See Table 74-1 for more information.

Message_number

A unique six-digit number that identifies the syslog message.

Message_text

A text string that describes the condition. This portion of the syslog message sometimes includes IP addresses, port numbers, or usernames.


Severity Levels

Table 74-1 lists the syslog message severity levels.

Table 74-1 Syslog Message Severity Levels

Level Number
Severity Level
Description

0

emergencies

System is unusable.

1

alert

Immediate action is needed.

2

critical

Critical conditions.

3

error

Error conditions.

4

warning

Warning conditions.

5

notification

Normal but significant conditions.

6

informational

Informational messages only.

7

debugging

Debugging messages only.



Note The ASA does not generate syslog messages with a severity level of zero (emergencies). This level is provided in the logging command for compatibility with the UNIX syslog feature, but is not used by the ASA.


Message Classes and Range of Syslog IDs

For a list of syslog message classes and the ranges of syslog message IDs that are associated with each class, see the Cisco ASA 5500 Series System Log Messages.

Filtering Syslog Messages

You can filter generated syslog messages so that only certain syslog messages are sent to a particular output destination. For example, you could configure the ASA to send all syslog messages to one output destination and to send a subset of those syslog messages to a different output destination.

Specifically, you can configure the ASA so that syslog messages are directed to an output destination according to the following criteria:

Syslog message ID number

Syslog message severity level

Syslog message class (equivalent to a functional area of the ASA)

You customize these criteria by creating a message list that you can specify when you set the output destination. Alternatively, you can configure the ASA to send a particular message class to each type of output destination independently of the message list.

You can use syslog message classes in two ways:

Specify an output location for an entire category of syslog messages using the logging class command.

Create a message list that specifies the message class using the logging list command.

The syslog message class provides a method of categorizing syslog messages by type, equivalent to a feature or function of the ASA. For example, the "vpnc" class denotes the VPN client.

All syslog messages in a particular class share the same initial three digits in their syslog message ID numbers. For example, all syslog message IDs that begin with the digits 611 are associated with the vpnc (VPN client) class. Syslog messages associated with the VPN client feature range from 611101 to 611323.

In addition, most of the ISAKMP syslog messages have a common set of prepended objects to help identify the tunnel. These objects precede the descriptive text of a syslog message when available. If the object is not known at the time the syslog message is generated, the specific "heading = value" combination is not displayed.

The objects are prepended as follows:

"Group = groupname, Username = user, IP = IP_address"

Where the group identifies the tunnel-group, the username is the username from the local database or AAA server, and the IP address is the public IP address of the remote access client or L2L peer.

Using Custom Message Lists

Creating a custom message list is a flexible way to exercise fine control over which syslog messages are sent to which output destination. In a custom syslog message list, you specify groups of syslog messages using any or all of the following criteria: severity level, message IDs, ranges of syslog message IDs, or by message class.

For example, message lists can be used to do the following:

Select syslog messages with severity levels of 1 and 2 and send them to one or more e-mail addresses.

Select all syslog messages associated with a message class (such as "ha") and save them to the internal buffer.

A message list can include multiple criteria for selecting messages. However, you must add each message selection criteria with a new command entry. It is possible to create a message list containing overlapping message selection criteria. If two criteria in a message list select the same message, the message is logged only once.

Licensing Requirements for Logging

The following table shows the licensing requirements for this feature:

Model
License Requirement

All models

Base License.


Prerequisites for Logging

Logging has the following prerequisites:

The syslog server must run a server program called "syslogd." Windows (except for Windows 95 and Windows 98) provides a syslog server as part of its operating system. For Windows 95 and Windows 98, you must obtain a syslogd server from another vendor.

To view logs generated by the ASA, you must specify a logging output destination. If you enable logging without specifying a logging output destination, the ASA generates messages, but does not save them to a location from which you can view them. You must specify each different logging output destination separately. For example, to designate more than one syslog server as an output destination, enter a new command for each syslog server.

Guidelines and Limitations

This section includes the guidelines and limitations for this feature:

Context Mode Guidelines

Supported in single and multiple context modes.

Firewall Mode Guidelines

Supported in routed and transparent firewall modes.

IPv6 Guidelines

Supports IPv6.

Additional Guidelines

ASDM may fail to load on ASA 8.2(2), because of insufficient DMA memory. This issue occurs if logging is enabled along with crypto IPSec and SSL tunnels. To resolve this issue, downgrade the ASA to Version 8.0.x or configure the logging queue to a value of 512 messages. After restoring the logging queue to the default value, reload the ASA to reclaim the required DMA memory.

Sending syslogs over TCP is not supported on a standby ASA.

The ASA supports the configuration of 16 syslog servers with the logging host command in single context mode. In multiple context mode, the limitation is 4 servers per context.

Configuring Logging

This section describes how to configure logging, and includes the following topics:

Enabling Logging

Sending Syslog Messages to an SNMP Server

Sending Syslog Messages to a Syslog Server

Sending Syslog Messages to the Console Port

Sending Syslog Messages to an E-mail Address

Sending Syslog Messages to ASDM

Sending Syslog Messages to a Telnet or SSH Session

Sending Syslog Messages to the Internal Log Buffer

Sending All Syslog Messages in a Class to a Specified Output Destination

Creating a Custom Message List

Enabling Secure Logging

Configuring the Logging Queue

Including the Date and Time in Syslog Messages

Generating Syslog Messages in EMBLEM Format

Including the Device ID in Syslog Messages

Disabling a Syslog Message

Changing the Severity Level of a Syslog Message

Limiting the Rate of Syslog Message Generation

Changing the Amount of Internal Flash Memory Available for Logs

Enabling Logging

To enable logging, enter the following command:

Command
Purpose
logging enable
Example:

hostname(config)# logging enable

Enables logging. To disable logging, enter the no logging enable command.


Sending Syslog Messages to an SNMP Server

To enable SNMP logging, enter the following command:

Command
Purpose
logging history [logging_list | level]
Example:

hostname(config)# logging history errors

Enables SNMP logging and specifies which messages are to be sent to SNMP servers. To disable SNMP logging, enter the no logging history command.


Sending Syslog Messages to a Syslog Server

To send syslog messages to a syslog server, perform the following steps:

 
Command
Purpose

Step 1 

logging host interface_name ip_address 
[tcp[/port] | udp[/port]] [format emblem] 
[permit-hostdown]
Example:

hostname(config)# logging host dmz1 192.168.1.5

Configures the ASA to send messages to a syslog server, which enables you to archive messages according to the available disk space on the server, and to manipulate logging data after it is saved. For example, you could specify actions to be executed when certain types of syslog messages are logged, extract data from the log and save the records to another file for reporting, or track statistics using a site-specific script. The format emblem keyword enables EMBLEM format logging for the syslog server (UDP only). The interface_name argument specifies the interface through which you access the syslog server. The ip_address argument specifies the IP address of the syslog server. The tcp[/port] or udp[/port] argument specifies that the ASA should use TCP or UDP to send syslog messages to the syslog server. The permit-hostdown keyword allows TCP logging to continue when the syslog server is down. You can configure the ASA to send data to a syslog server using either UDP or TCP, but not both. The default protocol is UDP. If you specify TCP, the ASA discovers when the syslog server fails and discontinues logging. If you specify UDP, the ASA continues to log messages whether or not the syslog server is operational. Valid port values are 1025 through 65535, for either protocol. The default UDP port is 514. The default TCP port is 1470.

Step 2 

logging trap {severity_level | message_list}
Example:

hostname(config)# logging trap errors

Specifies which syslog messages should be sent to the syslog server. You can specify the severity level number (0 through 7) or name. For example, if you set the severity level to 3, then the ASA sends syslog messages for severity levels 3, 2, 1, and 0. You can specify a custom message list that identifies the syslog messages to send to the syslog server.

Step 3 

logging facility number 
Example:

hostname(config)# logging facility 21

(Optional) Sets the logging facility to a value other than the default of 20, which is what most UNIX systems expect.

Sending Syslog Messages to the Console Port

To send syslog messages to the console port, enter the following command:

Command
Purpose
logging console {severity_level | message_list}
Example:

hostname(config)# logging console errors

Specifies which syslog messages should be sent to the console port.


Sending Syslog Messages to an E-mail Address

To send syslog messages to an e-mail address, perform the following steps:

 
Command
Purpose

Step 1 

logging mail {severity_level | message_list}
Example:

hostname(config)# logging mail high-priority

Specifies which syslog messages should be sent to an e-mail address. When sent by e-mail, a syslog message appears in the subject line of the e-mail message. For this reason, we recommend configuring this option to notify administrators of syslog messages with high severity levels, such as critical, alert, and emergency.

Step 2 

logging from-address email_address
Example:

hostname(config)# logging from-address xxx-001@example.com

Specifies the source e-mail address to be used when sending syslog messages to an e-mail address.

Step 3 

logging recipient-address e-mail_address 
[severity_level]
Example:
hostname(config)# logging recipient-address 
admin@example.com

Specifies the recipient e-mail address to be used when sending syslog messages to an e-mail address.

Step 4 

smtp-server ip_address

Example:

hostname(config)# smtp-server 10.1.1.1

Specifies the SMTP server to be used when sending syslog messages to an e-mail address.

Sending Syslog Messages to ASDM

To send syslog messages to ASDM, perform the following steps:

 
Command
Purpose

Step 1 

logging asdm {severity_level | message_list}

Example:

hostname(config)# logging asdm 2

Specifies which syslog messages should go to ASDM. The ASA sets aside a buffer area for syslog messages waiting to be sent to ASDM and saves messages in the buffer as they occur. The ASDM log buffer is a different buffer than the internal log buffer. When the ASDM log buffer is full, the ASA deletes the oldest syslog message to make room in the buffer for new ones. To control the number of syslog messages retained in the ASDM log buffer, you can change the size of the buffer.

Step 2 

logging asdm-buffer-size num_of_msgs
Example:

hostname(config)# logging asdm-buffer-size 200

Specifies the number of syslog messages to be retained in the ASDM log buffer. To erase the current content of the ASDM log buffer, enter the clear logging asdm command.

Sending Syslog Messages to a Telnet or SSH Session

To send syslog messages to a Telnet or SSH session, perform the following steps:

 
Command
Purpose

Step 1 

logging monitor {severity_level | message_list}
Example:

hostname(config)# logging monitor 6

Specifies which syslog messages should be sent to a Telnet or SSH session.

Step 2 

terminal monitor

Example:

hostname(config)# terminal monitor

Enables logging to the current session only. If you log out and then log in again, you need to reenter this command. To disable logging to the current session, enter the terminal no monitor command.

Sending Syslog Messages to the Internal Log Buffer

To send syslog messages to the internal log buffer, perform the following steps:

 
Command
Purpose

Step 1 

logging buffered {severity_level | message_list}
Example:

hostname(config)# logging buffered critical

hostname(config)# logging buffered level 2

hostname(config)# logging buffered notif-list

Specifies which syslog messages should be sent to the internal log buffer, which serves as a temporary storage location. New messages are appended to the end of the list. When the buffer is full, that is, when the buffer wraps, old messages are overwritten as new messages are generated, unless you configure the ASA to save the full buffer to another location. To clear the log buffer, enter the clear logging buffer command.

Step 2 

logging buffer-size bytes
Example:

hostname(config)# logging buffer-size 16384

Changes the size of the internal log buffer. The default buffer size is 4 KB.

Step 3 

Do one of the following:

 
logging flash-bufferwrap
Example:

hostname(config)# logging flash-bufferwrap

When saving the buffer content to another location, the ASA creates log files with names that use the following default time-stamp format:

LOG-YYYY-MM-DD-HHMMSS.TXT
 
        

where YYYY is the year, MM is the month, DD is the day of the month, and HHMMSS is the time in hours, minutes, and seconds.

The ASA continues to save new messages to the log buffer and saves the full log buffer content to internal flash memory.

 
logging ftp-bufferwrap
Example:

hostname(config)# logging ftp-bufferwrap

When saving the buffer content to another location, the ASA creates log files with names that use the following default time-stamp format:

LOG-YYYY-MM-DD-HHMMSS.TXT
 
        

where YYYY is the year, MM is the month, DD is the day of the month, and HHMMSS is the time in hours, minutes, and seconds.

The ASA continues saving new messages to the log buffer and saves the full log buffer content to an FTP server.

Step 4 

logging ftp-server server path username password
Example:

hostname(config)# logging ftp-server 10.1.1.1 /syslogs logsupervisor 1luvMy10gs

Identifies the FTP server on which you want to store log buffer content. The server argument specifies the IP address of the external FTP server. The path argument specifies the directory path on the FTP server where the log buffer data is to be saved. This path is relative to the FTP root directory. The username argument specifies a username that is valid for logging into the FTP server. The password argument specifies the password for the username specified.

Step 5 

logging savelog [savefile]
Example:

hostname(config)# logging savelog latest-logfile.txt

Saves the current log buffer content to internal flash memory.

Sending All Syslog Messages in a Class to a Specified Output Destination

To send all syslog messages in a class to a specified output destination, enter the following command:

Command
Purpose
logging class message_class {buffered | console | 
history | mail | monitor | trap} [severity_level]
Example:

hostname(config)# logging class ha buffered alerts

Overrides the configuration in the specific output destination command. For example, if you specify that messages at severity level 7 should go to the internal log buffer and that "ha" class messages at severity level 3 should go to the log buffer, then the latter configuration takes precedence. The buffered, history, mail, monitor, and trap keywords specify the output destination to which syslog messages in this class should be sent. The history keyword enables SNMP logging. The monitor keyword enables Telnet and SSH logging. The trap keyword enables syslog server logging. Select one destination per command line entry. To specify that a class should go to more than one destination, enter a new command for each output destination.


Creating a Custom Message List

To create a custom message list, perform the following steps:

 
Command
Purpose

Step 1 

logging list name {level level [class message_class] | message start_id[-end_id]}

Example:

hostname(config)# logging list notif-list level 3

Specifies criteria for selecting messages to be saved in the log buffer. For example, if you set the severity level to 3, then the ASA sends syslog messages for severity levels 3, 2, 1, and 0. The name argument specifies the name of the list. The level level argument specifies the severity level. The class message_class argument specifies a particular message class. The message start_id[-end_id] argument specifies an individual syslog message number or a range of numbers.

Note Do not use the names of severity levels as the name of a syslog message list. Prohibited names include "emergencies," "alert," "critical," "error," "warning," "notification," "informational," and "debugging." Similarly, do not use the first three characters of these words at the beginning of a filename. For example, do not use a filename that starts with the characters "err."

Step 2 

logging list name {level level [class message_class] | message start_id[-end_id]}

Example:

hostname(config)# logging list notif-list 104024-105999

hostname(config)# logging list notif-list level critical

hostname(config)# logging list notif-list level warning class ha

(Optional) Adds more criteria for message selection to the list. Enter the same command as in the previous step, specifying the name of the existing message list and the additional criterion. Enter a new command for each criterion that you want to add to the list. The specified criteria for syslog messages to be included in the list are the following:

Syslog message IDs that fall into the range of 104024 to 105999

All syslog messages with the critical severity level or higher (emergency, alert, or critical)

All "ha" class syslog messages with the warning severity level or higher (emergency, alert, critical, error, or warning)

Note A syslog message is logged if it satisfies any of these conditions. If a syslog message satisfies more than one of the conditions, the message is logged only once.

Enabling Secure Logging

To enable secure logging, enter the following command:

Command
Purpose
logging host interface_name syslog_ip [tcp/port | 
udp/port] [format emblem] [secure] 
Example:

hostname(config)# logging host inside 10.0.0.1 TCP/1500 secure

Enables secure logging. The interface_name argument specifies the interface on which the syslog server resides. The syslog_ip argument specifies the IP address of the syslog server. The port argument specifies the port (TCP or UDP) that the syslog server listens to for syslog messages. The tcp keyword specifies that the ASA should use TCP to send syslog messages to the syslog server. The udp keyword specifies that the ASA should use UDP to send syslog messages to the syslog server. The format emblem keyword enables EMBLEM format logging for the syslog server. The secure keyword specifies that the connection to the remote logging host should use SSL/TLS for TCP only.

Note Secure logging does not support UDP; an error occurs if you try to use this protocol.


Configuring the Logging Queue

To configure the logging queue, enter the following command:

Command
Purpose
logging queue message_count
Example:

hostname(config)# logging queue 300

Specifies the number of syslog messages that the ASA can hold in its queue before sending them to the configured output destination. The ASA has a fixed number of blocks in memory that can be allocated for buffering syslog messages while they are waiting to be sent to the configured output destination. The number of blocks required depends on the length of the syslog message queue and the number of syslog servers specified. The default queue size is 512 syslog messages. Valid values are from 0 to 8192 messages, depending on the platform. A setting of zero indicates that an unlimited number of syslog messages are allowed, that is, the queue size is limited only by block memory availability.

Note For the ASA 5505, the maximum queue size is 1024 messages. For the ASA 5510, the maximum queue size is 2048 messages. For all other platforms, the maximum queue size is 8192 messages.


Including the Device ID in Syslog Messages

To include the device ID in non-EMBLEM format syslog messages, enter the following command:

Command
Purpose
logging device-id [context-name | hostname | ipaddress 
interface_name | string text]
Example:

hostname(config)# logging device-id hostname

hostname(config)# logging device-id context-name

Configures the ASA to include a device ID in non-EMBLEM-format syslog messages. You can specify only one type of device ID for syslog messages. The context-name keyword indicates that the name of the current context should be used as the device ID (applies to multiple context mode only). If you enable the logging device ID for the admin context in multiple context mode, messages that originate in the system execution space use a device ID of system, and messages that originate in the admin context use the name of the admin context as the device ID. The hostname keyword specifies that the hostname of the ASA should be used as the device ID. The ipaddress interface_name argument specifies that the IP address of the interface specified as interface_name should be used as the device ID. If you use the ipaddress keyword, the device ID becomes the specified ASA interface IP address, regardless of the interface from which the syslog message is sent. This keyword provides a single, consistent device ID for all syslog messages that are sent from the device. The string text argument specifies that the text string should be used as the device ID. The string can include as many as 16 characters. You cannot use blank spaces or any of the following characters:

& (ampersand)

` (single quote)

" (double quote)

< (less than)

> (greater than)

? (question mark)

Note If enabled, the device ID does not appear in EMBLEM-formatted syslog messages or SNMP traps.


Generating Syslog Messages in EMBLEM Format

To generate syslog messages in EMBLEM format, enter the following command:

Command
Purpose

Do one of the following:

logging emblem
Example:

hostname(config)# logging emblem

Sends syslog messages in EMBLEM format to output destinations other than a syslog server.

logging host interface_name ip_address 
{tcp[/port] | udp[/port]] [format emblem]
Example:

hostname(config)# logging host interface_1 122.243.006.123 udp format emblem

Sends syslog messages in EMBLEM format to a syslog server over UDP using the default port of 514.


Including the Date and Time in Syslog Messages

To include the date and time in syslog messages, enter the following command:

Command
Purpose
logging timestamp
Example:

hostname(config)# logging timestamp LOG-2008-10-24-081856.TXT

Specifies that syslog messages should include the date and time that they were generated. To remove the date and time from syslog messages, enter the no logging timestamp command.


Disabling a Syslog Message

To disable a specified syslog message, enter the following command:

Command
Purpose
no logging message message_number
Example: E

hostname(config)# no logging message 113019

Prevents the ASA from generating a particular syslog message. To reenable a disabled syslog message, enter the logging message message_number command (for example, logging message 113019). To reenable logging of all disabled syslog messages, enter the clear config logging disabled command.


Changing the Severity Level of a Syslog Message

To change the severity level of a syslog message, enter the following command:

Command
Purpose
logging message message_ID level severity_level
Example:

hostname(config)# logging message 113019 level 5

Specifies the severity level of a syslog message. To reset the severity level of a syslog message to its default setting, enter the no logging message message_ID level current_severity_level command (for example, no logging message 113019 level 5). To reset the severity level of all modified syslog messages to their default settings, enter the clear configure logging level command.


Limiting the Rate of Syslog Message Generation

To limit the rate of syslog message generation, enter the following command:

Command
Purpose
logging rate-limit {unlimited | {num [interval]}} 
message syslog_id | level severity_level
Example:

hostname(config)# logging rate-limit 1000 600 level 6

Applies a specified severity level (1 through 7) to a set of messages or to an individual message within a specified time period. To reset the logging rate-limit to the default value, enter the clear running-config logging rate-limit command. To reset the logging rate-limit, enter the clear configure logging rate-limit command.


Changing the Amount of Internal Flash Memory Available for Logs

To change the amount of internal flash memory available for logs, perform the following steps:

 
Command
Purpose

Step 1 

logging flash-maximum-allocation kbytes
Example:

hostname(config)# logging flash-maximum-allocation 1200

Specifies the maximum amount of internal flash memory available for saving log files. By default, the ASA can use up to 1 MB of internal flash memory for log data. The default minimum amount of internal flash memory that must be free for the ASA to save log data is 3 MB.

If a log file being saved to internal flash memory would cause the amount of free internal flash memory to fall below the configured minimum limit, the ASA deletes the oldest log files to ensure that the minimum amount of memory remains free after saving the new log file. If there are no files to delete or if, after all old files have been deleted, free memory is still below the limit, the ASA fails to save the new log file.

Step 2 

logging flash-minimum-free kbytes
Example:

hostname(config)# logging flash-minimum-free 4000

Specifies the minimum amount of internal flash memory that must be free for the ASA to save a log file.

Monitoring Logging

To monitor logging, enter one of the following commands:

Command
Purpose
show logging

Shows the running logging configuration.

show logging message

Shows a list of syslog messages with modified severity levels and disabled syslog messages.

show logging message message_ID

Shows the severity level of a specific syslog message.

show logging queue

Shows the logging queue and queue statistics.

show logging rate-limit

Shows the disallowed syslog messages.

show running-config logging rate-limit

Shows the current logging rate-limit setting.


Examples

hostname(config)# show logging
Syslog logging: enabled
    Facility: 16
    Timestamp logging: disabled
    Standby logging: disabled
    Deny Conn when Queue Full: disabled
    Console logging: disabled
    Monitor logging: disabled
    Buffer logging: disabled
    Trap logging: level errors, facility 16, 3607 messages logged
        Logging to infrastructure 10.1.2.3
    History logging: disabled
    Device ID: 'inside' interface IP address "10.1.1.1"
    Mail logging: disabled
    ASDM logging: disabled
 
   

Configuration Examples for Logging

The following examples show how to control both whether a syslog message is enabled and the severity level of the specified syslog message:

hostname(config)# show logging message 403503
syslog 403503: default-level errors (enabled)
 
   
hostname(config)# logging message 403503 level 1
hostname(config)# show logging message 403503
syslog 403503: default-level errors, current-level alerts (enabled)
 
   
hostname(config)# no logging message 403503
hostname(config)# show logging message 403503
syslog 403503: default-level errors, current-level alerts (disabled)
 
   
hostname(config)# logging message 403503
hostname(config)# show logging message 403503
syslog 403503: default-level errors, current-level alerts (enabled)
 
   
hostname(config)# no logging message 403503 level 3
hostname(config)# show logging message 403503
syslog 403503: default-level errors (enabled)
 
   

Feature History for Logging

Table 74-2 lists the release history for this feature.

Table 74-2 Feature History for Logging 

Feature Name
Release
Feature Information

Logging

7.0(1)

Provides ASA network logging information through various output destinations, and includes the option to view and save log files.

Rate limit

7.0(4)

Limits the rate at which syslog messages are generated.

The following command was introduced: logging rate-limit

Logging list

7.2(1)

Creates a logging list to use in other commands to specify messages by various criteria (logging level, event class, and message IDs).

The following command was introduced: logging list

Secure logging

8.0(2)

Specifies that the connection to the remote logging host should use SSL/TLS. This option is valid only if the protocol selected is TCP.

The following command was modified: logging host

Logging class

8.0(4), 8.1(1)

Added support of another class (ipaa) for logging messages.

The following command was modified: logging class

Logging class and saved logging buffers

8.2(1)

Added support of another class (dap) for logging messages.

The following command was modified: logging class

Added support to clear the saved logging buffers (ASDM, internal, FTP, and flash).

The following command was introduced: clear logging queue bufferwrap