Home > Articles > Cisco Network Technology > General Networking > Cisco IOS IP Accounting Features

Cisco IOS IP Accounting Features

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Oct 19, 2007.

Chapter Description

This chapter describes the IP Accounting features in Cisco IOS and enables you to distinguish the different IP Accounting functions and understand SNMP MIB details. This chapter also provides a command-line reference.

IP Accounting is a very useful accounting feature in Cisco IOS, but it’s not as well known as other features, such as NetFlow. The fact that Cisco has considered replacing IP Accounting by adding new features to NetFlow potentially turns IP Accounting into a corner case solution. However, compared to NetFlow, IP Accounting offers some advantages that make it an interesting feature to investigate: easy results retrieval via a MIB and limited resource consumption. Furthermore, access-list accounting currently cannot be solved with the NetFlow implementation. Note that NetFlow recently added the export of the MAC address as a new information element. Refer to coverage of NetFlow Layer 2 and the Security Monitoring Exports feature in Chapter 7, “NetFlow.”

IP Accounting comes in four variations:

  • Basic IP Accounting, which this book calls “IP Accounting (Layer 3)”
  • IP Accounting Access Control List (ACL)
  • IP Accounting MAC Address
  • IP Accounting Precedence

Note that Cisco documentation is not always consistent for the different IP Accounting features. Therefore, this book uses the command-line interface (CLI) commands as titles, except for “IP Accounting Access Control List,” where the related CLI command is ip accounting access-violations.

This chapter discusses in detail each flavor of IP Accounting, using a basic structure. First, the fundamentals are explained, followed by an overview of CLI operations, and then SNMP operations. It concludes by comparing the IP Accounting features to the questions raised in Chapter 2, “Data Collection Methodology”:

  • What to collect?
  • Where and how to collect?
  • How to configure?
  • Who is the user?
  • Potential scenarios.

IP Accounting (Layer 3)

IP Accounting (Layer 3) collects the number of bytes and packets processed by the network element on a source and destination IP address basis. Only transit traffic that enters and leaves the router is measured, and only on an outbound basis. Traffic generated by the router or traffic terminating in the router is not included in the accounting statistics. IP Accounting (Layer 3) collects individual IP address details, so it can be used to identify specific users for usage-based billing. To provide the operator with the opportunity of “snapshot” collections in the network, IP Accounting (Layer 3) maintains two accounting databases: an active database and a checkpoint database. The active collection process always updates the active database and therefore constantly increments the counters while packets pass the router. To get a snapshot of the traffic statistics, a CLI command or SNMP request can be executed to copy the current status from the active database to the checkpoint database. This copy request can be automated across the network to be executed at the same time, and a Network Management application can later retrieve the accounting details from the checkpoint database to present consistent accounting data to the operator. The checkpoint database offers a “frozen” snapshot of the complete network. Trying to achieve the same result by synchronously polling entire MIB tables across multiple network elements would introduce some inaccuracies, and hence no real “frozen” snapshots. The collected data can be used for performance and trending applications that require collections at regular intervals. The snapshot function is unique to IP Accounting.

IP Accounting (Layer 3) Principles

The principles of IP Accounting (Layer 3) can be summarized as follows:

  • IP Layer 3 outbound (egress) traffic is collected.
  • Only transit traffic that enters and leaves the router is collected; traffic that is generated by the router or terminated in the router is not included.
  • IP Accounting (Layer 3) also collects IPX traffic. In this case, IPX source and destination addresses are reported instead of IP addresses.
  • Egress MPLS core traffic collection is a new feature.
  • Active and checkpoint databases enable “snapshot” collections.
  • Collection data is accessible via CLI and SNMP; however, the initial configuration must be done via CLI. To retrieve the collection results via SNMP, you need to enable SNMP first. When configuring SNMP, distinguish between read-only access and read-write access. For more details about SNMP configuration, see Chapter 4, “SNMP and MIBs.”
  • The MIB contains only 32-bit SNMP counters.

Supported Devices and IOS Versions

The following list defines the devices and Cisco IOS Software releases that support IP Accounting (Layer 3):

  • IP Accounting (Layer 3) was introduced in IOS 10.0.
  • It is supported on all routers, including Route Switch Module (RSM) and Multilayer Service Feature Card (MSFC), except for the Cisco 12000. Note that IP Accounting cannot account for MLS-switched traffic on the Catalyst 6500/7600, so it collects only a subset of traffic on these platforms.
  • It is supported on all physical interfaces and logical subinterfaces.
  • IP Accounting (Layer 3) runs on the top of all switching paths, except for autonomous switching, silicon switching engine (SSE) switching, and distributed switching (dCEF) on the interface. On the Cisco 7500 router, IP Accounting (Layer 3) causes packets to be switched on the Route Switch Processor (RSP) instead of the Versatile Interface Processor (VIP), which can cause additional performance degradation.

CLI Operations

Notable commands for configuring, verifying, and troubleshooting IP Accounting (Layer 3) are as follows:

  • router(config-if)# ip accounting output-packets

    enables IP Accounting (Layer 3) for output traffic on the interface.

  • router(config)# ip accounting-list [ip address] [ip address mask]

    defines filters to control the hosts for which IP Accounting (Layer 3) information is kept. The filters are similar to an aggregation scheme and can be used to reduce the number of collected records. If filters are applied, details such as number of packets and bytes are kept only for the traffic that matches the filters, while all others are aggregated into “transit records.”

  • router(config)# ip accounting-transits count

    controls the number of transit records that are stored in the IP Accounting (Layer 3) database. Transit entries are those that do not match any of the filters specified by the global configuration command ip accounting-list. If no filters are defined, no transit entries are possible. The default number of transit records that are stored in the IP Accounting (Layer 3) database is 0.

    Note that the term “transit” in this case refers to packets that are not matched by the filter statements. In the IP Accounting (Layer 3) definition, “transit” refers to packets that traverse the router, compared to traffic that is generated at the router or destined for the router.

  • router(config)# ip accounting-threshold count

    sets the maximum number of accounting entries to be created. The accounting threshold defines the maximum number of entries (source and destination address pairs) that are accumulated. The default accounting threshold is 512 entries, which results in a maximum table size of 12,928 bytes. The threshold counter applies to both the active and checkpoint tables.

    The threshold value depends on the traffic mix, because different traffic types create different records for the source and destination address pairs. Whenever the table is full, the new entries (overflows) are not accounted. However, show ip accounting displays the overflows: “Accounting threshold exceeded for X packets and Y bytes.” Alternatively, these values are available in the MIB: actLostPkts (lost IP packets due to memory limitations) and actLostByts (total bytes of lost IP packets). You should monitor the overflows number, at least during the deployment phase, to find the right balance between the number of entries and memory consumption.

  • router# show ip accounting [checkpoint] output-packets

    displays the active accounting or checkpoint database.

  • router# clear ip accounting

    copies the content of the active database to the checkpoint database and clears the active database afterward.

  • router# clear ip accounting checkpoint

    clears the checkpoint database.

SNMP Operations

The OLD-CISCO-IP-MIB has two tables:

  • lipAccountingTable, the active database
  • lipCkAccountingTable, the checkpoint database

The MIB variable actCheckPoint must be read first and then set to the same value that was read to copy the active database into the checkpoint database. After a successful SNMP set request, actCheckPoint is incremented by 1. Setting actCheckPoint is the equivalent of the clear ip accounting CLI command. A Network Management application can retrieve the MIB variable lipCkAccountingTable to analyze stable data in the checkpoint database. There is no SNMP variable to erase the content of the checkpoint database; however, setting actCheckPoint again flushes the checkpoint database and copies the content of the active database.

Details of the IP Accounting MIB (OLD-CISCO-IP-MIB) are as follows:

  • Active database—The lipAccountingTable table contains four relevant components:

    • — actSrc is the active database source.
    • — actDst is the active database destination.
    • — actPkts is the active database packets.
    • — actByts is the active database bytes.

    The table indexes are actSrc and actDst.

  • Checkpoint database—The lipCkAccountingTable table contains four relevant components:

    • — ckactSrc is the checkpoint database source.
    • — ckactdDst is the checkpoint database destination.
    • — ckactPkts is the checkpoint database packets.
    • — ckactByts is the checkpoint database bytes.

    The table indexes are ckactSrc and ckactDst.

  • actCheckPoint MIB variable

Examples (CLI and SNMP)

The following example provides a systematic introduction for configuring and monitoring IP Accounting (Layer 3) and displays the results for both CLI and SNMP.

Initial Configuration

Initially, both the active database (lipAccountingTable) and checkpoint database (lipCkAccountingTable) are empty, as shown from the router CLI and from the SNMP tables.

router#show ip accounting output-packets
   Source          Destination               Packets            Bytes
   Accounting data age is 0
router#show ip accounting checkpoint output-packet
   Source          Destination               Packets            Bytes
   Accounting data age is 0

The router is accessed with SNMP2c (SNMP version 2c), the read community string is public, and the SNMP tool net-snmp is used.

SERVER % snmpwalk -c public -v 2c <router> lipAccountingTable
    actDst.0.0.0.0.0.0.0.0 = IpAddress: 0.0.0.0
    actByts.0.0.0.0.0.0.0.0 = INTEGER: 0
SERVER % snmpwalk -c public -v 2c <router> lipCkAccountingTable
    ckactDst.0.0.0.0.0.0.0.0 = IpAddress: 0.0.0.0
    ckactByts.0.0.0.0.0.0.0.0 = INTEGER: 0

The IP Accounting (Layer 3) configuration is straightforward:

router(config)#int serial 0/0
router(config-if)#ip accounting output-packets
router(config-if)#exit

Collection Monitoring

After configuring IP Accounting (Layer 3), the active database populates:

router#show ip accounting output-packet
   Source           Destination             Packets         Bytes
 192.1.1.110        192.1.1.97                 5             500
 192.1.1.110        192.1.1.26                 5             500

The corresponding MIB table shows the identical entries:

SERVER % snmptable -Ci -Cb -c public -v 2c <router> lipAccountingTable
                           index           Src          Dst   Pkts   Byts
          192.1.1.110.192.1.1.26 192.1.1.110 192.1.1.26          5    500
          192.1.1.110.192.1.1.97 192.1.1.110 192.1.1.97          5    500

At this point, the checkpoint database is still empty. The active database content is cleared by copying its content to the checkpoint database:

router#clear ip accounting

As an alternative, the clear ip accounting mechanism can be mimicked by using the actCheckPoint MIB variable procedure. That means reading the content of the MIB variable and setting it again to the same value that was read:

SERVER % snmpget -c public -v 2c <router> actCheckPoint.0
       actCheckPoint.0 = INTEGER: 0
SERVER % snmpset -c private -v 2c <router> actCheckPoint.0 i 0
       actCheckPoint.0 = INTEGER: 0
      SERVER % snmpget -c public -v 2c <router> actCheckPoint.0
       actCheckPoint.0 = INTEGER: 1

The two entries just discussed are now in the checkpoint database, but the active database is empty:

router#show ip accounting output-packets
   Source           Destination             Packets              Bytes
   Accounting data age is 0
router#show ip accounting output-packets checkpoint output-packets
   Source           Destination             Packets             Bytes
 192.1.1.110        192.1.1.97                 5                 500
 192.1.1.110        192.1.1.26                 5                 500
SERVER % snmptable -Ci -Cb -c public -v 2c <router> lipCkAccountingTable
                           index           Src          Dst   Pkts   Byts
          192.1.1.110.192.1.1.26 192.1.1.110 192.1.1.26          5    500
          192.1.1.110.192.1.1.97 192.1.1.110 192.1.1.97          5    500
2. IP Accounting Access Control List (ACL) | Next Section

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children

This site is not directed to children under the age of 13.

Marketing

Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020