Networking Software (IOS & NX-OS)

Table Of Contents

BGP Policy Accounting

Finding Feature Information

Contents

Prerequisites

Information About BGP Policy Accounting

BGP Policy Accounting Overview

Benefits of BGP Policy Accounting

How to Configure BGP Policy Accounting

Specifying the Match Criteria for BGP Policy Accounting

Classifying the IP Traffic and Enabling BGP Policy Accounting

Verifying BGP Policy Accounting

Monitoring and Maintaining BGP Policy Accounting

Configuration Examples

Specifying the Match Criteria for BGP Policy Accounting Example

Classifying the IP Traffic and Enabling BGP Policy Accounting Example

Additional References

Related Documents

MIBs

Technical Assistance

Feature Information for BGP Policy Accounting

BGP Policy Accounting

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Border Gateway Protocol (BGP) policy accounting measures and classifies IP traffic that is sent to, or received from, different peers. Policy accounting is enabled on an input interface, and counters based on parameters such as community list, autonomous system number, or autonomous system path are assigned to identify the IP traffic.

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 BGP Policy Accounting" section.

Use Cisco Feature Navigator to find information about platform support and Cisco 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

•Information About BGP Policy Accounting

•How to Configure BGP Policy Accounting

•Configuration Examples

•Additional References

•Feature Information for BGP Policy Accounting

Prerequisites

Before using the BGP Policy Accounting feature, you must enable BGP and CEF or dCEF on the router.

Information About BGP Policy Accounting

•BGP Policy Accounting Overview

•Benefits of BGP Policy Accounting

BGP Policy Accounting Overview

Border Gateway Protocol (BGP) policy accounting measures and classifies IP traffic that is sent to, or received from, different peers. Policy accounting is enabled on an input interface, and counters based on parameters such as community list, autonomous system number, or autonomous system path are assigned to identify the IP traffic.

Using the BGP table-map command, prefixes added to the routing table are classified by BGP attribute, autonomous system number, or autonomous system path. Packet and byte counters are incremented per input interface. A Cisco IOS policy-based classifier maps the traffic into one of eight possible buckets, representing different traffic classes.

Using BGP policy accounting, you can account for traffic according to the route it traverses. Service providers (SPs) can identify and account for all traffic by customer and bill accordingly. In Figure 1, BGP policy accounting can be implemented in Router A to measure packet and byte volumes in autonomous system buckets. Customers are billed appropriately for traffic that is routed from a domestic, international, or satellite source.

Figure 1 Sample Topology for BGP Policy Accounting

BGP policy accounting using autonomous system numbers can be used to improve the design of network circuit peering and transit agreements between Internet service providers (ISPs).

Benefits of BGP Policy Accounting

Account for IP Traffic Differentially

BGP policy accounting classifies IP traffic by autonomous system number, autonomous system path, or community list string, and increments packet and byte counters. Service providers can account for traffic and apply billing, according to the route specific traffic traverses.

Efficient Network Circuit Peering and Transit Agreement Design

Implementing BGP policy accounting on an edge router can highlight potential design improvements for peering and transit agreements.

How to Configure BGP Policy Accounting

•Specifying the Match Criteria for BGP Policy Accounting (required)

•Classifying the IP Traffic and Enabling BGP Policy Accounting (required)

•Verifying BGP Policy Accounting (optional)

•Monitoring and Maintaining BGP Policy Accounting (optional)

Specifying the Match Criteria for BGP Policy Accounting

The first task in configuring BGP policy accounting is to specify the criteria that must be matched. Community lists, autonomous system paths, or autonomous system numbers are examples of BGP attributes that can be specified and subsequently matched using a route map.

To specify the BGP attribute to use for BGP policy accounting and create the match criteria in a route map, use the following commands in global configuration mode:

	Command	Purpose
Step 1	Router(config)# ip community-list community-list-number {permit | deny} community-number	Creates a community list for BGP and controls access to it. This step must be repeated for each community to be specified.
Step 2	Router(config)# route-map map-name [permit | deny] [sequence-number]	Enters route-map configuration mode and defines the conditions for policy routing. The map-name argument identifies a route map. The optional permit and deny keywords work with the match and set criteria to control how the packets are accounted for. The optional sequence-number argument indicates the position a new route map is to have in the list of route maps already configured with the same name.
Step 3	Router(config-route-map)# match community-list community-list-number [exact]	Matches a BGP community.
Step 4	Router(config-route-map)# set traffic-index bucket-number	Indicates where to output packets that pass a match clause of a route map for BGP policy accounting.

Classifying the IP Traffic and Enabling BGP Policy Accounting

After a route map has been defined to specify match criteria, you must configure a way to classify the IP traffic before enabling BGP policy accounting.

Using the table-map command, BGP classifies each prefix it adds to the routing table based on the match criteria. When the bgp-policy accounting command is configured on an interface, BGP policy accounting is enabled.

To classify the IP traffic and enable BGP policy accounting, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# router bgp as-number	Configures a BGP routing process and enters router configuration mode for the specified routing process.
Step 2	Router(config-router)# table-map route-map-name	Classifies BGP prefixes entered in the routing table.
Step 3	Router(config-router)# network network-number [mask network-mask]	Specifies a network to be advertised by the BGP routing process.
Step 4	Router(config-router)# neighbor ip-address remote-as as-number	Specifies a BGP peer by adding an entry to the BGP routing table.
Step 5	Router(config-router)# exit	Exits to global configuration mode.
Step 6	Router(config)# interface interface-type interface-number	Specifies the interface type and number and enters interface configuration mode.
Step 7	Router(config-if)# no ip directed-broadcast	Configures the interface to drop directed broadcasts destined for the subnet to which that interface is attached, rather than being broadcast. This is a security issue.
Step 8	Router(config-if)# ip address ip-address mask	Configures the interface with an IP address.
Step 9	Router(config-if)# bgp-policy accounting	Enables BGP policy accounting for the interface.

Verifying BGP Policy Accounting

To verify that BGP policy accounting is operating, perform the following steps:

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Step 1 Enter the show ip cef EXEC command with the detail keyword to learn which accounting bucket is assigned to a specified prefix.

In this example, the output is displayed for the prefix 192.168.5.0. It shows that the accounting bucket number 4 (traffic_index 4) is assigned to this prefix.

Router# show ip cef 192.168.5.0 detail

192.168.5.0/24, version 21, cached adjacency to POS7/2

0 packets, 0 bytes, traffic_index 4

  via 10.14.1.1, 0 dependencies, recursive

   next hop 10.14.1.1, POS7/2 via 10.14.1.0/30

   valid cached adjacency

Step 2 Enter the show ip bgp EXEC command for the same prefix used in Step 1—192.168.5.0— to learn which community is assigned to this prefix.

In this example, the output is displayed for the prefix 192.168.5.0. It shows that the community of 100:197 is assigned to this prefix.

Router# show ip bgp 192.168.5.0

BGP routing table entry for 192.168.5.0/24, version 2

Paths: (1 available, best #1)

  Not advertised to any peer

  100

    10.14.1.1 from 10.14.1.1 (32.32.32.32)

      Origin IGP, metric 0, localpref 100, valid, external, best

      Community: 100:197

Step 3 Enter the show cef interface policy-statistics EXEC command to display the per-interface traffic statistics.

In this example, the output shows the number of packets and bytes that have been assigned to each accounting bucket:

LC-Slot7# show cef interface policy-statistics

POS7/0 is up (if_number 8)

Bucket    Packets               Bytes

1          0                      0

2          0                      0

3          50                     5000

4          100                    10000

5          100                    10000

6          10                     1000

7          0                      0

8          0                      0

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Monitoring and Maintaining BGP Policy Accounting

To monitor and maintain the BGP Policy Accounting feature, use the following commands in EXEC mode, as needed:

Command	Purpose
Router# show cef interface [type number] policy-statistics	Displays detailed CEF policy statistical information for all interfaces.
Router# show ip bgp [network] [network mask] [longer-prefixes]	Displays entries in the BGP routing table.
Router# show ip cef [network [mask]] [detail]	Displays entries in the Forwarding Information Base (FIB) or FIB summary information.

Configuration Examples

•Specifying the Match Criteria for BGP Policy Accounting Example

•Classifying the IP Traffic and Enabling BGP Policy Accounting Example

Specifying the Match Criteria for BGP Policy Accounting Example

In the following example, BGP communities are specified in community lists, and a route map named set_bucket is configured to match each of the community lists to a specific accounting bucket using the set traffic-index command:

ip community-list 30 permit 100:190

ip community-list 40 permit 100:198

ip community-list 50 permit 100:197

ip community-list 60 permit 100:296

!

route-map set_bucket permit 10

match community 30

set traffic-index 2

!

route-map set_bucket permit 20

match community 40

set traffic-index 3

!

route-map set_bucket permit 30

match community 50

set traffic-index 4

!

route-map set_bucket permit 40

match community 60

set traffic-index 5

Classifying the IP Traffic and Enabling BGP Policy Accounting Example

In the following example, BGP policy accounting is enabled on POS interface 7/0 and the table-map command is used to modify the bucket number when the IP routing table is updated with routes learned from BGP:

router bgp 65000

 table-map set_bucket

 network 10.15.1.0 mask 255.255.255.0

 neighbor 10.14.1.1 remote-as 65100

!

ip classless

ip bgp-community new-format 

!

interface POS7/0

 ip address 10.15.1.2 255.255.255.0

 no ip directed-broadcast

 bgp-policy accounting

 no keepalive

 crc 32

 clock source internal

Additional References

Related Documents

Related Topic	Document Title
Cisco IOS commands	Cisco IOS Master Commands List, All Releases
BGP commands	Cisco IOS IP Routing: BGP Command Reference
BGP configuration information	Cisco BGP Features Roadmap" module chapter of the Cisco IOS IP Routing: BGP Configuration Guide
Cisco Express Forwarding (CEF) and distributed CEF (dCEF) commands	Cisco IOS IP Switching Command Reference
Cisco Express Forwarding (CEF) and distributed CEF (dCEF) configuration information	"Cisco Express Forwarding Overview" module of the Cisco IOS Switching Services Configuration Guide

MIBs

MIB	MIBs Link
•CISCO-BGP-POLICY-ACCOUNTING-MIB Note CISCO-BGP-POLICY-ACCOUNTING-MIB is only available in the Cisco IOS Release 12.0(9)S, 12.0(17)ST, and later releases. This MIB is not available on any mainline and T-train release.	To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs

Technical Assistance

Description	Link
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.	http://www.cisco.com/cisco/web/support/index.html

Feature Information for BGP Policy Accounting

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which 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.

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

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Table 1 Feature Information for BGP Policy Accounting

Feature Name	Releases	Feature Information
BGP Policy Accounting	12.0(9)S 12.0(17)ST 12.2(13)T 15.0(1)S 12.2(50)SY	Border Gateway Protocol (BGP) policy accounting measures and classifies IP traffic that is sent to, or received from, different peers. Policy accounting is enabled on an input interface, and counters based on parameters such as community list, autonomous system number, or autonomous system path are assigned to identify the IP traffic. The following commands were introduced or modified: •bgp-policy •set traffic-index •show cef interface policy-statistics •show ip bgp •show ip cef

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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.

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