BGP aggregate-address attribute-map

Using the aggregate-address command with no arguments will create an aggregate entry in the BGP routing table if there are any more-specific BGP routes available that fall in the specified range. The aggregate route will be advertised as coming from your autonomous system and has the atomic aggregate attribute set to show that information might be missing. (By default, the atomic aggregate attribute is set unless you specify the as-set keyword.)

Attributes are inherited from the prefixes, use the attribute-map argument to manipulate the aggregate-address attributes.

Video Demonstration

from: Cisco IOS IP Routing: BGP Command Reference

aggregate-address

To create an aggregate entry in a Border Gateway Protocol (BGP) database, use the aggregate-address command in address family or router configuration mode. To disable this function, use the no form of this command.

aggregate-address address mask [as-set] [as-confed-set] [summary-only] [ suppress-map map-name ] [ advertise-map map-name ] [ attribute-map map-name ]

no aggregate-address address mask [as-set] [as-confed-set] [summary-only] [ suppress-map map-name ] [ advertise-map map-name ] [ attribute-map map-name ]

Syntax Description

address	Aggregate address.
mask	Aggregate mask.
as-set	(Optional) Generates autonomous system set path information.
as-confed-set	(Optional) Generates autonomous confederation set path information.
summary-only	(Optional) Filters all more-specific routes from updates.
suppress-map map-name	(Optional) Specifies the name of the route map used to select the routes to be suppressed.
advertise-map map-name	(Optional) Specifies the name of the route map used to select the routes to create AS_SET origin communities.
attribute-map map-name	(Optional) Specifies the name of the route map used to set the attribute of the aggregate route.

Command Default

The atomic aggregate attribute is set automatically when an aggregate route is created with this command unless the as-set keyword is specified.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release	Modification
10.0	This command was introduced.
11.1(20)CC	The nlri unicast, nlri multicast, and nlri unicast multicast keywords were added.
12.0(2)S	The nlri unicast, nlri multicast, and nlri unicast multicast keywords were added.
12.0(7)T	The nlri unicast, nlri multicast, and nlri unicast multicast keywords were removed. Address family configuration mode support was added.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SRB	Support for IPv6 was added.
12.2(33)SB	This command was integrated into Cisco IOS Release 12.2(33)SB.
12.2(33)SXI	This command was integrated into Cisco IOS Release 12.2(33)SXI.
12.2(33)SRE	The as-confed-set keyword was added.
Cisco IOS XE Release 3.1S	This command was introduced on Cisco ASR 1000 series routers.

Usage Guidelines

You can implement aggregate routing in BGP and Multiprotocol BGP (mBGP) either by redistributing an aggregate route into BGP or mBGP, or by using the conditional aggregate routing feature.

Using the aggregate-addresscommand with no keywords will create an aggregate entry in the BGP or mBGP routing table if any more-specific BGP or mBGP routes are available that fall within the specified range. (A longer prefix that matches the aggregate must exist in the Routing Information Base (RIB).) The aggregate route will be advertised as coming from your autonomous system and will have the atomic aggregate attribute set to show that information might be missing. (By default, the atomic aggregate attribute is set unless you specify the as-set keyword.)

Using the as-setkeyword creates an aggregate entry using the same rules that the command follows without this keyword, but the path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized. Do not use this form of the aggregate-addresscommandwhen aggregating many paths, because this route must be continually withdrawn and updated as autonomous system path reachability information for the summarized routes changes.

Using the as-confed-set keyword creates an aggregate entry using the same rules that the command follows without this keyword. This keyword performs the same function as theas-set keyword, except that it generates autonomous confed set path information.

Using the summary-onlykeyword not only creates the aggregate route (for example, 192.*.*.*) but also suppresses advertisements of more-specific routes to all neighbors. If you want to suppress only advertisements to certain neighbors, you may use the neighbor distribute-list command, with caution. If a more-specific route leaks out, all BGP or mBGP routers will prefer that route over the less-specific aggregate you are generating (using longest-match routing).

Using the suppress-mapkeyword creates the aggregate route but suppresses advertisement of specified routes. You can use the match clauses of route maps to selectively suppress some more-specific routes of the aggregate and leave others unsuppressed. IP access lists and autonomous system path access lists match clauses are supported.

Using the advertise-mapkeyword selects specific routes that will be used to build different components of the aggregate route, such as AS_SET or community. This form of theaggregate-addresscommand is useful when the components of an aggregate are in separate autonomous systems and you want to create an aggregate with AS_SET, and advertise it back to some of the same autonomous systems. You must remember to omit the specific autonomous system numbers from the AS_SET to prevent the aggregate from being dropped by the BGP loop detection mechanism at the receiving router. IP access lists and autonomous system path access lists match clauses are supported.

Using the attribute-mapkeyword allows attributes of the aggregate route to be changed. This form of the aggregate-addresscommand is useful when one of the routes forming the AS_SET is configured with an attribute such as the community no-export attribute, which would prevent the aggregate route from being exported. An attribute map route map can be created to change the aggregate attributes.

Examples

Examples

In the following example, an aggregate BGP address is created in router configuration mode. The path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized.

Router(config)# router bgp 50000 
Router(config-router)# aggregate-address 10.0.0.0 255.0.0.0 as-set 

Examples

In the following example, an aggregate BGP address is created in address family configuration mode and applied to the multicast database under the IP Version 4 address family. Because the summary-only keyword is configured, more-specific routes are filtered from updates.

Router(config)# router bgp 50000 
Router(config-router)# address-family ipv4 multicast 
Router(config-router-af)# aggregate-address 10.0.0.0 255.0.0.0 summary-only 

Examples

In the following example, a route map called MAP-ONE is created to match on an AS-path access list. The path advertised for this route will be an AS_SET consisting of elements contained in paths that are matched in the route map.

Router(config)# ip as-path access-list 1 deny ^1234_ 
Router(config)# ip as-path access-list 1 permit .* 
Router(config)# ! 
Router(config)# route-map MAP-ONE 
Router(config-route-map)# match ip as-path 1 
Router(config-route-map)# exit 
Router(config)# router bgp 50000 
Router(config-router)# address-family ipv4 
Router(config-router-af)# aggregate-address 10.0.0.0 255.0.0.0 as-set advertise-map
MAP-ONE 
Router(config-router-af)# end
 

Related Commands

Command	Description
address-family ipv4(BGP)	Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.
ip as-path access-list	Defines a BGP autonomous system path access list.
match ip address	Distributes any routes that have a destination network number address that is permitted by a standard or extended access list, and performs policy routing on packets.
neighbor distribute-list	Distributes BGP neighbor information in an access list.
route-map (IP)	Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing.

Files:
Topology
Configs
BGP Configuration