BGP Support for Named Extended Community Lists

Table Of Contents

BGP Support for Named Extended Community Lists

Contents

How to Configure Named Extended Community Lists

Configuring Named Extended CommunityLists

Verifying Named Extended Community-list Configuration

Configuration Examples for Named Extended Community Lists

Named Extended Community-list Configuration: Example

Named Extended Community-list Verification: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

ip extcommunity-list

show ip extcommunity-list

BGP Support for Named Extended Community Lists

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The BGP Support for Named Extended Community Lists feature introduces the ability to configure extended community lists using names in addition to the existing numbered format.

Feature History for the BGP Support for Named Extended Community Lists feature

Release	Modification
12.2(25)S	This feature was introduced.
12.3(11)T	This feature was integrated into Cisco IOS Release 12.3(11)T.
12.2(27)SBC	This feature was integrated into Cisco IOS Release 12.2(27)SBC.

Finding Support Information for Platforms and Cisco IOS Software Images

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Contents

•How to Configure Named Extended Community Lists

•Configuration Examples for Named Extended Community Lists

•Additional References

•Command Reference

How to Configure Named Extended Community Lists

This section contains the following tasks:

•Configuring Named Extended CommunityLists

•Verifying Named Extended Community-list Configuration

Configuring Named Extended CommunityLists

Perform this task to configure a named extended community list.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip extcommunity-list expanded-list-number [expanded list-name {permit | deny} [regular-expression] | standard-list-number | standard list-name {permit | deny} [rt extcom-value] [soo extcom-value] ]

4. end

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 extcommunity-list expanded-list-number [ expanded list-name {permit | deny} [regular-expression] | standard-list-number | standard list-name {permit | deny} [rt extcom-value] [soo extcom-value]] Example: Router(config)# ip extcommunity-list standard NAMED_LIST permit rt 64512:10	Creates an extended community-list and controls access to it. •The example creates a standard named extended community list.
Step 4	end Example: Router(config)# end	Exits global configuration mode and enters privileged EXEC mode.

Verifying Named Extended Community-list Configuration

Perform this task to verify the configuration of a named extended community list.

SUMMARY STEPS

1. show ip extcommunity-list [list-number | list-name]

DETAILED STEPS

	Command or Action	Purpose
Step 1	show ip extcommunity-list [list-number | list-name] Example: Router# show ip extcommunity-list	Displays routes that are permitted by an extended community list.

Configuration Examples for Named Extended Community Lists

The following examples show how to configure and verify this feature:

•Named Extended Community-list Configuration: Example

•Named Extended Community-list Verification: Example

Named Extended Community-list Configuration: Example

The following example creates and configures a named extended community list that will permit routes only from route target 64512:10 and will implicitly deny all other routes:

Router(config)# ip extcommunity-list standard NAMED_LIST permit rt 64512:10

Named Extended Community-list Verification: Example

The following example uses the show ip extcommunity-list EXEC command to display routes that are locally permitted by a named extended community list:

Router# show ip extcommunity-list 

Standard extended community-list NAMED_LIST

     10 deny RT:64512:10

Additional References

The following sections provide references related to the BGP Support for Named Extended Community Lists feature.

Related Documents

Related Topic	Document Title
BGP commands	Cisco IOS IP Command Reference, Volume 2 of 4: Routing Protocols, Release 12.3T
BGP configuration tasks	Cisco IOS IP Configuration Guide, Release 12.3
Regular Expressions	"Regular Expressions" appendix of the Cisco IOS Terminal Services Configuration Guide

Standards

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

MIBs

MIBs	MIBs Link
No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.	To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL: http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs

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

Technical Assistance

Description	Link
Technical Assistance Center (TAC) home page, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, tools, and lots more. Registered Cisco.com users can log in from this page to access even more content.	TAC Home Page: http://www.cisco.com/public/support/tac/home.shtml BGP Support Page: http://www.cisco.com/cgi-bin/Support/browse/psp_view.pl?p=Internetworking:BGP

Command Reference

This section documents modified commands.

•ip extcommunity-list

•show ip extcommunity-list

ip extcommunity-list

To create an extended community list to configure Virtual Private Network (VPN) route filtering, use the ip extcommunity-list command in global configuration mode. To delete the extended community list, use the no form of this command.

Global Configuration Mode CLI

ip extcommunity-list expanded-list | expanded list-name {permit | deny} [regular-expression] | standard-list | standard list-name {permit | deny} [rt value] [soo value]

no ip extcommunity-list expanded-list | expanded list-name | standard-list | standard list-name

To enter IP Extended community-list configuration mode to create or configure an extended community-list, use the ip extcommunity-list command in global configuration mode. To delete the entire extended community list, use the no form of this command. To delete a single entry, use the no form in IP Extended community-list configuration mode.

ip extcommunity-list expanded-list | expanded list-name | standard-list | standard list-name

no ip extcommunity-list expanded-list | expanded list-name | standard-list | standard list-name

Expanded IP Extended Community-List Configuration Mode CLI

[sequence-number] deny [regular-expression] | exit | permit [regular-expression] | resequence [starting-sequence] [sequence-increment]

default {sequence-number | deny [regular-expression] | exit | permit [regular-expression] | resequence [starting-sequence] [sequence-increment]}

no {sequence-number | deny [regular-expression] | permit [regular-expression] | resequence [starting-sequence] [sequence-increment]}

Standard IP Extended Community-List Configuration Mode CLI

[sequence-number] deny [rt value] [soo value] | exit | permit [rt value] [soo value] | resequence [starting-sequence] [sequence-increment]

default {sequence-number | deny [rt value] [soo value] | exit | permit [rt value] [soo value] | resequence [starting-sequence] [sequence-increment]}

no {sequence-number | deny [rt value | soo value] | permit [rt value] [soo value] | resequence [starting-sequence] [sequence-increment]}

Syntax Description

expanded-list	An expanded list number from 100 to 500 that identifies one or more permit or deny groups of extended communities.
standard-list	A standard list number from 1 to 99 that identifies one or more permit or deny groups of extended communities.
expanded list-name	Creates an expanded named extended community list and enters IP Extended community-list configuration mode.
standard list-name	Creates a standard named extended community list and enters IP Extended community-list configuration mode.
permit	Permits access for a matching condition.
deny	Denies access for a matching condition.
regular-expression	(Optional) An input string pattern to match against.
rt	(Optional) Specifies the route target (RT) extended community attribute. The rt keyword can be configured only with standard extended community lists and not expanded community lists.
soo	(Optional) Specifies the site of origin (SOO) extended community attribute. The soo keyword can be configured only with standard extended community lists and not expanded community lists.
value	Specifies the route target or site of origin extended community value. This value can be entered in one of the following formats: •autonomous-system-number : network-number •ip-address : network-number
sequence-number	(Optional) The sequence number of a named or numbered extended community list. This value can be a number from 1 to 2147483647.
default	(Optional) Sets a keyword or argument to default behavior or value.
exit	(Optional) Exits from IP Extended community-list configuration mode.
resequence	(Optional) Changes the sequences of extended community list entries to the default sequence numbering or to the specified sequence numbering. Extended community entries are sequenced by ten number increments by default.
starting-sequence	(Optional) Specifies the number for the first entry in an extended community list.
sequence-increment	(Optional) Specifies the increment range for each subsequent extended community entry.

Defaults

Extended community exchange is not enabled by default. It is enabled on a per-neighbor basis with the neighbor send-community command.

Once a permit value has been configured to match a given set of extended communities, the extended community list defaults to an implicit deny for all other values.

Extended community list entries start with the number 10 and increment by ten for each subsequent entry when no sequence number is specified, when default behavior is configured, and when an extended community list is resequenced without specifying the first entry number or the increment range for subsequent entries.

Command Modes

Global configuration
IP Extended community-list configuration

Command History

Release	Modification
12.1	This command was introduced.
12.0(22)S	The maximum number of expanded community list numbers was increased from 199 to 500.
12.2(15)T	The maximum number of expanded community list numbers was increased from 199 to 500.
12.2(25)S	Support for the following was added in Cisco IOS Release 12.2(25)S: •Extended community-list sequencing •IP Extended community configuration mode •Named extended community lists
12.3(11)T	Support for the following was added in Cisco IOS Release 12.3(11)T: •Extended community-list sequencing •IP Extended community configuration mode •Named extended community lists
12.2(27)SBC	This command was integrated into the Cisco IOS Release 12.2(27)SBC.

Usage Guidelines

The ip extcommunity-list command is used to configure named or numbered extended community lists. Extended community attributes are used to filter routes for VPN routing and forwarding instances (VRFs) and Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs). All of the standard rules of access lists apply to the configuration of extended community lists. The route target (RT) and site of origin (SOO) extended community attributes are supported by the standard range of extended community lists. Regular expressions are supported in expanded extended community lists. For information about configuring regular expressions, see the Regular Expressions appendix of the Cisco IOS Terminal Services Configuration Guide.

Route Target Extended Community Attribute

The route target (RT) extended community attribute is configured with the rt keyword. This attribute is used to identify a set of sites and VRFs that may receive routes that are tagged with the configured route target. Configuring the route target extended attribute with a route allows that route to be placed in the per-site forwarding tables that are used for routing traffic that is received from corresponding sites.

Site of Origin Extended Community Attribute

The site of origin (SOO) extended community attribute is configured with the soo keyword. This attribute uniquely identifies the site from which the provider edge (PE) router learned the route. All routes learned from a particular site must be assigned the same site of origin extended community attribute, regardless if a site is connected to a single PE router or multiple PE routers. Configuring this attribute prevents routing loops from occurring when a site is multihomed. The SOO extended community attribute is configured on the interface and is propagated into BGP through redistribution. The SOO should not be configured for stub sites or sites that are not multihomed.

IP Extended Community-List Configuration Mode

Named and numbered extended community lists can be configured in IP Extended community-list configuration mode. To enter IP Extended community-list configuration mode, enter the ip extcommunity-list command with either the expanded or standard keyword followed by the extended community list name. This configuration mode supports all of the functions that are available in global configuration mode. In addition, you can perform the following operations:

•Configure sequence numbers for extended community list entries

•Resequence existing sequence numbers for extended community list entries

•Configure an extended community list to use default values

Extended Community List Processing

When multiple values are configured in the same extended community list statement, a logical AND condition is created. All extended community values must match to satisfy an AND condition. When multiple values are configured in separate extended community list statements, a logical OR condition is created. The first list that matches a condition is processed.

Examples

Standard Extended Community-List Configuration Example

In the following example, an extended community list is configured that permits routes from route target 64512:10 and site of origin 65400:20 and denies routes from route target 65424:30 and site of origin 64524:40. List 1 shows a logical OR condition; the first match is processed. List 2 shows a logical AND condition; all community values must match in order for list 2 to be processed.

Router(config)# ip extcommunity-list 1 permit rt 64512:10

Router(config)# ip extcommunity-list 1 permit soo 65400:20

Router(config)# ip extcommunity-list 2 deny rt 65424:30 soo 64524:40

Expanded Extended Community-List Configuration Example

In the following example, an expanded extended community list is configured to deny advertisements from any path through or from autonomous system 65534 from being advertised to the 192.168.1.2 neighbor:

Router(config)# ip extcommunity-list 500 deny _65412_

Router(config)# router bgp 50000

Router(config-router)# address-family vpnv4

Router(config-router-af)# neighbor 172.16.1.1 remote-as 65412

Router(config-router-af)# neighbor 172.16.1.1 neighbor send-community extended

Router(config-router-af)# neighbor 192.168.1.2 remote-as 65534

Router(config-router-af)# neighbor 192.168.1.2 neighbor send-community extended

Router(config-router-af)# end

Named Extended Community-List Configuration Example

In the following example, a named extended community list is configured that will permit routes only from route target 65505:50. All other routes are implicitly denied.

Router(config)# ip extcommunity-list standard NAMED_LIST permit rt 65505:50

IP Extended Community-List Configuration Mode Example

In the following example, an expanded named extended community list is configured in IP Extended community-list configuration mode. A list entry is created with a sequence number 10 that will permit a route target or route origin pattern that matches any network number extended community from autonomous system 65412.

Router(config)# ip extcommunity-list RED 

Router(config-extcom-list)# 10 permit 65412:[0-9][0-9][0-9][0-9][0-9]_ 

Router(config-extcom-list)# exit

Extended Community-List Resequencing Example

In the following example, the first list entry is resequenced to the number 50 and each subsequent entry is configured to increment by 100:

Router(config)# ip extcommunity-list BLUE 

Router(config-extcom-list)# resequence 50 100

Router(config-extcom-list)# exit

Related Commands

Command	Description
export map	Configures an export route map for a VRF.
match extcommunity	Matches a BGP VPN extended community list.
set extcommunity	Sets BGP extended community attributes.
show ip extcommunity-list	Displays routes that are permitted by the extended community list.
show route-map	Displays configured route maps.

show ip extcommunity-list

To display routes that are permitted by an extended community list, use the show ip extcommunity-list command in EXEC mode.

show ip extcommunity-list [list-number | list-name]

Syntax Description

list-number	(Optional) Specifies an extended community list number from 1 to 500. A standard extended community list number is from 1 to 99. An expanded extended list is from 100 to 500.
list-name	(Optional) Specifies an extended community list name.

Defaults

If a specific extended community list number is not specified when the show ip extcommunity-list command is entered, all locally configured extended community lists will be displayed by default.

Command Modes

EXEC

Command History

Release	Modification
12.1	This command was introduced.
12.2(25)S 12.3(11)T	Support for named extended community lists was added. Minor formatting changes were made to the output.
12.2(27)SBC	This command was integrated into the Cisco IOS Release 12.2(27)SBC.

Examples

The following is sample output from the show ip extcommunity-list command in EXEC mode:

Router# show ip extcommunity-list 

Standard extended community-list 1

     10 permit RT:64512:10

     20 permit SoO:65400:20

     30 deny RT:65424:30 SoO:64524:40

Standard extended community-list 99

     10 permit RT:65504:40 SoO:65505:50

     20 deny RT:65406:60 SoO:65307:70

Expanded extended community-list LIST_NAME 

     10 permit 0-9* A-Z* a-z*

Table 1 describes the significant fields shown in the display.

Table 1 show ip extcommunity-list Field Descriptions 

Field	Description
... extended community-list....	The type of extended community-list (standard or expanded), and the name or number of the extended community list.
10	The sequence number of the extended community list entry. 10 is the lowest default sequence number. Extended community lists increment by 10 when default values are configured.
permit/deny	Indicates a permit or deny sequence entry.
RT/SoO	Indicates the route target or the site of origin used in a standard extended community list.
0-9* A-Z* a-z*	Regular expression used in an expanded extended community list.

Related Commands

Command	Description
show route-map	Displays configured route maps.

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