Table Of Contents

ACL Syslog Correlation

Finding Feature Information

Contents

Prerequisites for ACL Syslog Correlation

Information About ACL Syslog Correlation

ACL Syslog Correlation Tags

ACE Syslog Messages

How to Configure ACL Syslog Correlation

Enabling Hash Value Generation on a Router

Examples

Disabling Hash Value Generation on a Router

Examples

Configuring ACL Syslog Correlation Using a User-Defined Cookie

Restrictions

Examples

Configuring ACL Syslog Correlation Using a Hash Value

Examples

Changing the ACL Syslog Correlation Tag Value

Troubleshooting Tips

Configuration Examples for ACL Syslog Correlation

Configuring ACL Syslog Correlation Using a User-Defined Cookie: Example

Configuring ACL Syslog Correlation using a Hash Value: Example

Changing the ACL Syslog Correlation Tag Value: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for ACL Syslog Correlation

ACL Syslog Correlation

---

First Published: October 10, 2008

Last Updated: October 10, 2008

The Access Control List (ACL) Syslog Correlation feature appends a tag (either a user-defined cookie or a router-generated MD5 hash value) to access control entry (ACE) syslog entries. This tag uniquely identifies the ACE , within the ACL, that generated the syslog entry.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for ACL Syslog Correlation" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS, Catalyst OS, and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for ACL Syslog Correlation

•Information About ACL Syslog Correlation

•How to Configure ACL Syslog Correlation

•Configuration Examples for ACL Syslog Correlation

•Additional References

•Feature Information for ACL Syslog Correlation

Prerequisites for ACL Syslog Correlation

Before you configure the ACL Syslog Correlation feature you should understand the concepts in the "IP Access List Overview" module.

The ACL Syslog Correlation feature appends a user-defined cookie or a router-generated hash value to ACE messages in the syslog. These values are only appended to ACE messages when the log option is enabled for the ACE.

Information About ACL Syslog Correlation

You should understand the following concepts before configuring the ACL Syslog Correlation feature:

•ACL Syslog Correlation Tags

•ACE Syslog Messages

ACL Syslog Correlation Tags

The ACL Syslog Correlation feature appends a tag (either a user-defined cookie or a router-generated MD5 hash value) to ACE syslog entries. This tag uniquely identifies the ACE that generated the syslog entry.

Network management software can use the tag to identify which ACE generated a specific syslog event. For example, network administrators can select an ACE rule in the network management application and can then view the corresponding syslog events for that ACE rule.

To append a tag to the syslog message, the ACE that generates the syslog event must have the log option enabled. The system appends only one type of tag (either a user-defined cookie or a router-generated MD5 hash value) to each message.

To specify a user-defined cookie tag, the user must enter the cookie value when configuring the ACE log option. The cookie must be in alpha-numeric form, it cannot be greater than 64 characters, and it cannot start with hex-decimal notation (such as 0x).

To specify a router-generated MD5 hash value tag, the hash-generation mechanism must be enabled on the router and the user must not enter a cookie value while configuring the ACE log option.

ACE Syslog Messages

When a packet is matched against an ACE in an ACL, the system checks whether the log option is enabled for that event. If the log option is enabled and the ACL Syslog Correlation feature is configured on the router, the system attaches the tag to the syslog message. The tag is displayed at the end of the syslog message, in addition to the standard information.

The following is a sample syslog message showing a user-defined cookie tag:

Jun 5 12:55:44.359: %SEC-6-IPACCESSLOGP: list logacl permitted tcp 192.168.16.1(38402) -> 
192.168.16.2(23), 1 packet [User_permiited_ACE]

The following is a sample syslog message showing a hash value tag:

Jun 5 12:55:44.359: %SEC-6-IPACCESSLOGP: list logacl permitted tcp 192.168.16.1(38402) -> 
192.168.16.2(23), 1 packet [0x723E6E12]

How to Configure ACL Syslog Correlation

This section includes the following tasks:

•Enabling Hash Value Generation on a Router

•Disabling Hash Value Generation on a Router

•Configuring ACL Syslog Correlation Using a User-Defined Cookie

•Configuring ACL Syslog Correlation Using a Hash Value

•Changing the ACL Syslog Correlation Tag Value

Enabling Hash Value Generation on a Router

Perform this task to configure the router to generate an MD5 hash value for each log-enabled ACE in the system that is not configured with a user-defined cookie.

When the hash value generation setting is enabled, the system checks all existing ACEs and generates a hash value for each ACE that requires one. When the hash value generation setting is disabled, all previously generated hash values are removed from the system.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip access-list logging hash-generation

4. end

5. show ip access-list [access-list-number | access-list-name]

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	ip access-list logging hash-generation Example: Router(config)# ip access-list logging hash-generation	Enables hash value generation on the router. •If an ACE exists that is log enabled, and requires a hash value, the router automatically generates the value and displays the value on the console.
Step 4	end Example: Router(config)# end	(Optional) Exits global configuration mode and returns to privileged EXEC mode.
Step 5	show ip access-list access-list-number or show ip access-list access-list-name Example: Router# show ip access-list 101 or Example: Router# show ip access-list acl	(Optional) Displays the contents of the numbered or named IP access list. •Review the output to confirm that the access list for a log-enabled ACE includes the generated hash value.

Examples

The following is sample output from the show ip access-list command when hash generation is enabled for the specified access-list.

Router# show ip access-list 101

Extended IP access list 101

10 permit tcp any any log (hash = 0x75F078B9)

Router# show ip access-list acl

Extended IP access list acl

10 permit tcp any any log (hash = 0x3027EB26)

Disabling Hash Value Generation on a Router

Perform this task to disable hash value generation on the router. When the hash value generation setting is disabled, all previously generated hash values are removed from the system.

SUMMARY STEPS

1. enable

2. configure terminal

3. no ip access-list logging hash-generation

4. end

5. show ip access-list [access-list-number | access-list-name]

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	no ip access-list logging hash-generation Example: Router(config)# no ip access-list logging hash-generation	Disables hash value generation on the router. •The system removes any previously created hash values from the system.
Step 4	end Example: Router(config)# end	(Optional) Exits global configuration mode and returns to privileged EXEC mode.
Step 5	show ip access-list access-list-number or show ip access-list access-list-name Example: Router# show ip access-list 101 or Example: Router# show ip access-list acl	(Optional) Displays the contents of the IP access list. •Review the output to confirm that the access list for a log-enabled ACE does not have a generated hash value.

Examples

The following is sample output from the show ip access-list command when hash generation is disabled and no cookie value has been specified.

Router# show ip access-list 101

Extended IP access list 101

10 permit tcp any any log

Router# show ip access-list acl

Extended IP access list acl

10 permit tcp any any log

Configuring ACL Syslog Correlation Using a User-Defined Cookie

Perform this task to configure the ACL Syslog Correlation feature on a router for a specific access list, using a user-defined cookie as the syslog message tag.

---

Note The example in this section shows how to configure the ACL Syslog Correlation feature using a user-defined cookie for a numbered access list. However, you can configure the ACL Syslog Correlation feature using a user-defined cookie for both numbered and named access lists, and for both standard and extended access lists.

---

Restrictions

The following restrictions apply when choosing the user-defined cookie value:

•The maximum number of characters is 64.

•The cookie cannot start with hexadecimal notation (such as 0x).

•The cookie cannot be the same as, or a subset of, the following keywords: reflect, fragment, time-range. For example, reflect and ref are not valid values. However, the cookie can start with the keywords. For example, reflectedACE and fragment_33 are valid values

•The cookie must contains only alphanumeric characters.

SUMMARY STEPS

1. enable

2. configure terminal

3. access-list access-list-number permit protocol source destination log word

4. end

5. show ip access-list access-list-number

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	access-list access-list-number permit protocol source destination log word Example: Router(config)# access-list 101 permit tcp host 10.1.1.1 host 10.1.1.2 log UserDefinedValue	Defines an extended IP access list and a user-defined cookie value. •Enter the cookie value as the word argument.
Step 4	end Example: Router(config)# end	(Optional) Exits global configuration mode and returns to privileged EXEC mode.
Step 5	show ip access-list access-list-number Example: Router# show ip access-list 101	(Optional) Displays the contents of the IP access list. •Review the output to confirm that the access list includes the user-defined cookie value.

Examples

The following is sample output from the show ip access-list command for an access list with a user-defined cookie value.

Router# show ip access-list 101

Extended IP access list 101

30 permit tcp host 10.1.1.1 host 10.1.1.2 log (tag = UserDefinedValue)

Configuring ACL Syslog Correlation Using a Hash Value

Perform this task to configure the ACL Syslog Correlation feature on a router for a specific access list, using a router-generated hash value as the syslog message tag.

---

Note The steps in this section shows how to configure the ACL Syslog Correlation feature using a router-generated hash value for a numbered access list. However, you can configure the ACL Syslog Correlation feature using a router-generated hash value for both numbered and named access lists, and for both standard and extended access lists.

---

SUMMARY STEPS

1. enable

2. configure terminal

3. ip access-list logging hash-generation

4. access-list access-list-number permit protocol source destination log

5. end

6. show ip access-list access-list-number

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	ip access-list logging hash-generation Example: Router(config)# ip access-list logging hash-generation	Enables hash value generation on the router. •If an ACE exists that is log enabled, and requires a hash value, the router automatically generates the value and displays the value on the console.
Step 4	access-list access-list-number permit protocol source destination log Example: Router(config)# access-list 102 permit tcp host 10.1.1.1 host 10.1.1.2 log	Defines an extended IP access list. •Enable the log option for the access list, but do not specify a cookie value. •The router automatically generates a hash value for the newly defined access list.
Step 5	end Example: Router(config)# end	(Optional) Exits global configuration mode and returns to privileged EXEC mode.
Step 6	show ip access-list access-list-number Example: Router# show ip access-list 102	(Optional) Displays the contents of the IP access list. •Review the output to confirm that the access list includes the router-generated hash value.

Examples

The following is sample output from the show ip access-list command for an access list with a router-generated hash value.

Router# show ip access-list 102

Extended IP access list 102

10 permit tcp host 10.1.1.1 host 10.1.1.2 log (hash = 0x7F9CF6B9)

Changing the ACL Syslog Correlation Tag Value

Perform this task to change the value of the user-defined cookie or replace a router-generated hash value with a user-defined cookie.

---

Note The steps in this section shows how to change the ACL Syslog Correlation tag value on a numbered access list. However, you can change the ACL Syslog Correlation tag value for both numbered and named access lists, and for both standard and extended access lists.

---

SUMMARY STEPS

1. enable

2. show access-list

3. configure terminal

4. access-list access-list-number permit protocol source destination log word

5. end

6. show ip access-list access-list-number

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	show access-list Example: Router(config)# show access-list	(Optional) Displays the contents of the access list.
Step 3	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 4	access-list access-list-number permit protocol source destination log word Example: Router(config)# access-list 101 permit tcp host 10.1.1.1 host 10.1.1.2 log NewUDV OR Router(config)# access-list 101 permit tcp any any log replacehash	Modifies the cookie or changes the hash value to a cookie. •You must enter the entire access list configuration command, replacing the previous tag value with the new tag value.
Step 5	end Example: Router(config)# end	(Optional) Exits global configuration mode and returns to privileged EXEC mode.
Step 6	show ip access-list access-list-number Example: Router# show ip access-list 101	(Optional) Displays the contents of the IP access list. •Review the output to confirm the changes.

Troubleshooting Tips

Use the debug ip access-list hash-generation command to display access list debug information. The following is an example of the debug command output:

Router# debug ip access-list hash-generation

 Syslog hash code generation debugging is on

Router# show debug

IP ACL:

 Syslog hash code generation debugging is on

Router# no debug ip access-list hash-generation 

 Syslog hash code generation debugging is off

Router# show debug

Router#

Configuration Examples for ACL Syslog Correlation

This section provides the following configuration examples:

•Configuring ACL Syslog Correlation Using a User-Defined Cookie: Example

•Configuring ACL Syslog Correlation using a Hash Value: Example

•Changing the ACL Syslog Correlation Tag Value: Example

Configuring ACL Syslog Correlation Using a User-Defined Cookie: Example

The following example shows how to configure the ACL Syslog Correlation feature on a router using a user-defined cookie.

Router#

Router# debug ip access-list hash-generation

Syslog MD5 hash code generation debugging is on

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# access-list 33 permit 10.10.10.6 log cook_33_std

Router(config)# do show ip access 33

Standard IP access list 33

10 permit 10.10.10.6 log (tag = cook_33_std)

Router(config)# end

Router#

Configuring ACL Syslog Correlation using a Hash Value: Example

The following examples shows how to configure the ACL Syslog Correlation feature on a router using a router-generated hash value.

Router# debug ip access-list hash-generation

Syslog MD5 hash code generation debugging is on

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# access-list 33 permit 10.10.10.7 log

Router(config)#

*Nov 7 13:51:23.615: %IPACL-HASHGEN: Hash Input: 33 standard permit 10.10.10.7

Hash Output: 0xCE87F535

Router(config)# do show ip access 33 

Standard IP access list 33

    10 permit 10.10.10.6 log (tag = cook_33_std)

    20 permit 10.10.10.7 log (hash = 0xCE87F535)

Router(config)#

Changing the ACL Syslog Correlation Tag Value: Example

The following example shows how to replace an existing access list user-defined cookie with a new cookie value, and how to replace a router-generated hash value with a user-defined cookie value.

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# do show ip access-list 101

Extended IP access list 101

    10 permit tcp host 10.1.1.1 host 10.1.1.2 log (tag = MyCookie)

    20 permit tcp any any log (hash = 0x75F078B9)

Router(config)# access-list 101 permit tcp host 10.1.1.1 host 10.1.1.2 log NewUDV

Router(config)# do show access-list

Extended IP access list 101

    10 permit tcp host 10.1.1.1 host 10.1.1.2 log (tag = NewUDV)

    20 permit tcp any any log (hash = 0x75F078B9)

Router(config)# access-list 101 permit tcp any any log replacehash

Router(config)# do show access-list

Extended IP access list 101

    10 permit tcp host 10.1.1.1 host 10.1.1.2 log (tag = NewUDV)

    20 permit tcp any any log (tag = replacehash)

Additional References

The following sections provide references related to the ACL Syslog Correlation feature.

Related Documents

Related Topic	Document Title
Configuring and Creating ACLs	Creating an IP Access List and Applying it to an Interface
ACL commands	Cisco IOS Security Command Reference
Cisco IOS commands	Master Commands List, All Releases

Standards

Standard	Title
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature	—

MIBs

MIB	MIBs Link
None	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

RFCs

RFC	Title
None	—

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/techsupport

Feature Information for ACL Syslog Correlation

Table 1 lists the release history for this feature. For information on a feature in this technology that is not documented here, see the IP Access List Roadmap.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS, Catalyst OS, and Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

---

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

---

Table 1 Feature Information for ACL Syslog Correlation 

Feature Name	Releases	Feature Information
ACL Syslog Correlation	12.4(22)T	The following commands were introduced or modified: ip access-list logging hash-generation, debug ip access-list hash-generation, access-list (IP extended), access-list (IP standard), permit, permit (Catalyst 6500 series switches), permit (IP).

CCDE, CCENT, Cisco Eos, Cisco HealthPresence, the Cisco logo, Cisco Lumin, Cisco Nexus, Cisco StadiumVision, Cisco TelePresence, Cisco WebEx, DCE, and Welcome to the Human Network are trademarks; Changing the Way We Work, Live, Play, and Learn and Cisco Store are service marks; and Access Registrar, Aironet, AsyncOS, Bringing the Meeting To You, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, CCSP, CCVP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Collaboration Without Limitation, EtherFast, EtherSwitch, Event Center, Fast Step, Follow Me Browsing, FormShare, GigaDrive, HomeLink, Internet Quotient, IOS, iPhone, iQuick Study, IronPort, the IronPort logo, LightStream, Linksys, MediaTone, MeetingPlace, MeetingPlace Chime Sound, MGX, Networkers, Networking Academy, Network Registrar, PCNow, PIX, PowerPanels, ProConnect, ScriptShare, SenderBase, SMARTnet, Spectrum Expert, StackWise, The Fastest Way to Increase Your Internet Quotient, TransPath, WebEx, and the WebEx logo are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.

All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0812R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

© 2008 Cisco Systems, Inc. All rights reserved.