BGP aggregate-address

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.)

Using the summary-only keyword not only creates the aggregate route (for example, 193.*.*.*) but will also suppress advertisements of more-specific routes to all neighbors. If you only want to suppress advertisements to certain neighbors, you may use the neighbor distribute-list command, with caution. If a more specific route leaks out, all BGP speakers will prefer that route over the less-specific aggregate you are generating (using longest-match routing).

R11 & R10 "show ip bgp" Without Aggregate-address:

R11 & R10 "show ip bgp" With Aggregate-address:

R11 & R10 "show ip bgp" With Aggregate-address Summary-Only:

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.

Files:
Topology
Configs
BGP Configuration

Note:
TCL Script from: Packet Pushers

BGP Confederations

BGP Confederations: An Alternative to Full Mesh Internal BGP (IBGP)

iBGP requires a full mesh between all BGP-speaking routers; route reflectors modify iBGP split-horizon rules, and BGP confederations modify iBGP AS-path processing

The full-mesh requirement is relaxed through introduction of member autonomous systems into which the original autonomous system is split.

The addition autonomous system numbers are hidden from the outside world by modified AS-path update procedures.

The intraconfederation segment is removed from the AS path by the egress confederation router prior to prepending the official AS number when sending a BGP update to an external AS.

Intraconfederation eBGP sessions act like eBGP sessions from a session.establishment perspective, and they act like iBGP sessions from the BGP attribute-propagation perspective.

Output after BGP is configured:

Video Demonstration

from: Cisco IOS IP Routing: BGP Command Reference

bgp confederation identifier

To specify a BGP confederation identifier, use the bgp confederation identifier command in router configuration mode. To remove the confederation identifier, use the no form of this command.

bgp confederation identifier autonomous-system-number

no bgp confederation identifier autonomous-system-number

Syntax Description

autonomous-system-number

Number of an autonomous system number used to configure a single autonomous system number to identify a group of smaller autonomous systems as a single confederation. Number in the range from 1 to 65535. •In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, 4-byte autonomous system numbers are supported in the range from 65536 to 4294967295 in asplain notation and in the range from 1.0 to 65535.65535 in asdot notation. •In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, 4-byte autonomous system numbers are supported in the range from 1.0 to 65535.65535 in asdot notation only. For more details about autonomous system number formats, see the router bgp command.

Command Default

No BGP confederation identifier is identified.

Command Modes

Router configuration (config-router)

Command History

Release	Modification
10.3	This command was introduced.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(14)SX	This command was integrated into Cisco IOS Release 12.2(14)SX.
12.0(32)S12	This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.
12.0(32)SY8	This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.
12.4(24)T	This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.
Cisco IOS XE Release 2.3	This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.
12.2(33)SXI1	This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.
12.0(33)S3	This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.
Cisco IOS XE Release 2.4	This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.
12.2(33)SRE	This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.
12.2(33)XNE	This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

Usage Guidelines

The bgp confederation identifier command is used to configure a single autonomous system number to identify a group of smaller autonomous systems as a single confederation.

A confederation can be used to reduce the internal BGP (iBGP) mesh by dividing a large single autonomous system into multiple subautonomous systems and then grouping them into a single confederation. The subautonomous systems within the confederation exchange routing information like iBGP peers. External peers interact with the confederation as if it were a single autonomous system.

Each subautonomous system is fully meshed within itself and has a few connections to other autonomous systems within the confederation. Next hop, Multi Exit Discriminator (MED), and local preference information is preserved throughout the confederation, allowing you to retain a single Interior Gateway Protocol (IGP) for all the autonomous systems.

In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, the Cisco implementation of 4-byte autonomous system numbers uses asplain—65538 for example—as the default regular expression match and output display format for autonomous system numbers, but you can configure 4-byte autonomous system numbers in both the asplain format and the asdot format as described in RFC 5396. To change the default regular expression match and output display of 4-byte autonomous system numbers to asdot format, use the bgp asnotation dot command followed by the clear ip bgp * command to perform a hard reset of all current BGP sessions.

In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, the Cisco implementation of 4-byte autonomous system numbers uses asdot—1.2 for example—as the only configuration format, regular expression match, and output display, with no asplain support.

If one member of a BGP confederation is identified using a 4-byte autonomous system number, all other members of a BGP confederation must be upgraded to support 4-byte autonomous system numbers.

Examples

In the following example, the routing domain is divided into autonomous systems 50001, 50002, 50003, 50004, 50005, and 50006 and is identified by the confederation identifier 50007. Neighbor 10.2.3.4 is a peer inside of the routing domain confederation. Neighbor 10.4.5.6 is a peer outside of the routing domain confederation. To external peers and routing domains, the confederation appears as a single autonomous system with the number 50007.

router bgp 50000 

 bgp confederation identifier 50007 

 bgp confederation peers 50001 50002 50003 50004 50005 50006 

 neighbor 10.2.3.4 remote-as 50001 

 neighbor 10.4.5.6 remote-as 40000 

 end 

In the following example, the routing domain is divided into autonomous systems using 4-byte autonomous system numbers 65538, 65536, and 65550 in asplain format and identified by the confederation identifier 65545. Neighbor 192.168.1.2 is a peer inside of the routing domain confederation. Neighbor 192.168.2.2 is a peer outside of the routing domain confederation. To external peers and routing domains, the confederation appears as a single autonomous system with the number 65545. This example requires Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, or a later release.

router bgp 65550 

 bgp confederation identifier 65545

 bgp confederation peers 65538 65536 65550

 neighbor 192.168.1.2 remote-as 65536

 neighbor 192.168.2.2 remote-as 65547

 end 

In the following example, the routing domain is divided into autonomous systems using 4-byte autonomous system numbers 1.2 and 1.0 in asdot format and is identified by the confederation identifier 1.9. Neighbor 192.168.1.2 is a peer inside of the routing domain confederation. Neighbor 192.168.2.2 is a peer outside of the routing domain confederation. To external peers and routing domains, the confederation appears as a single autonomous system with the number 1.9. This example requires Cisco IOS Release 12.0(32)S12, 12.4(24)T, or Cisco IOS XE Release 2.3 where asdot notation is the only format for 4-byte autonomous system numbers. This configuration can also be performed using Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, or later releases.

router bgp 1.14

 bgp confederation identifier 1.9

 bgp confederation peers 1.2 1.0

 neighbor 192.168.1.2 remote-as 1.0

 neighbor 192.168.2.2 remote-as 1.11

 end 

Related Commands

Command	Description
bgp asnotation dot	Changes the default display and the regular expression match format of BGP 4-byte autonomous system numbers from asplain (decimal values) to dot notation.
bgp confederation peers	Configures subautonomous systems to belong to a single confederation.
router bgp	Configures the BGP routing process.

bgp confederation peers

To configure subautonomous systems to belong to a single confederation, use the bgp confederation peers command in router configuration mode. To remove an autonomous system from the confederation, use the no form of this command.

bgp confederation peers autonomous-system-number [... autonomous-system-number]

no bgp confederation peers autonomous-system-number [... autonomous-system-number]

Syntax Description

autonomous-system-number

Autonomous system numbers for BGP peers that will belong to the confederation. Number in the range from 1 to 65535. The autonomous system number of the local router is not allowed to be specified in this command. •In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, 4-byte autonomous system numbers are supported in the range from 65536 to 4294967295 in asplain notation and in the range from 1.0 to 65535.65535 in asdot notation. •In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, 4-byte autonomous system numbers are supported in the range from 1.0 to 65535.65535 in asdot notation only. For more details about autonomous system number formats, see the router bgp command.

Command Default

No BGP peers are configured to be members of a BGP confederation.

Command Modes

Router configuration (config-router)

Command History

Release	Modification
10.3	This command was introduced.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(14)SX	This command was integrated into Cisco IOS Release 12.2(14)SX.
12.0(32)S12	This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.
12.0(32)SY8	This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.
12.4(24)T	This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.
Cisco IOS XE Release 2.3	This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.
12.2(33)SXI1	This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.
12.0(33)S3	This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.
Cisco IOS XE Release 2.4	This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.
12.2(33)SRE	This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.
12.2(33)XNE	This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

Usage Guidelines

The bgp confederation peers command is used to configure multiple autonomous systems as a single confederation. The ellipsis (...) in the command syntax indicates that your command input can include multiple values for the autonomous-system-number argument.

The autonomous system number of the router on which this command is being specified is not allowed in this command (not allowed as a confederation peer). If you specify the local router's autonomous system number in the bgp confederation peers command, the error message "Local member-AS not allowed in confed peer list" will appear.

The autonomous systems specified in this command are visible internally to the confederation. Each autonomous system is fully meshed within itself. Use the bgp confederation identifier command to specify the confederation to which the autonomous systems belong.

In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4 , and later releases, the Cisco implementation of 4-byte autonomous system numbers uses asplain—65538 for example—as the default regular expression match and output display format for autonomous system numbers, but you can configure 4-byte autonomous system numbers in both the asplain format and the asdot format as described in RFC 5396. To change the default regular expression match and output display of 4-byte autonomous system numbers to asdot format, use the bgp asnotation dot command followed by the clear ip bgp * command to perform a hard reset of all current BGP sessions.

In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, the Cisco implementation of 4-byte autonomous system numbers uses asdot—1.2 for example—as the only configuration format, regular expression match, and output display, with no asplain support.

If one member of a BGP confederation is identified using a 4-byte autonomous system number, all other members of a BGP confederation must be upgraded to support 4-byte autonomous system numbers.

Examples

In the following example, autonomous systems 50001, 50002, 50003, 50004, and 50005 are configured to belong to a single confederation under the identifier 50000:

router bgp 50000 

 bgp confederation identifier 50000 

 bgp confederation peers 50001 50002 50003 50004 50005 

In the following example, the routing domain is divided into autonomous systems using 4-byte autonomous system numbers 65538 and 65536, and is identified by the confederation identifier 65545. Neighbor 192.168.1.2 is a peer inside of the routing domain confederation. Neighbor 192.168.2.2 is a peer outside of the routing domain confederation. To external peers and routing domains, the confederation appears as a single autonomous system with the number 65545. This example requires Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, or a later release.

router bgp 65550 

 bgp confederation identifier 65545

 bgp confederation peers 65538 65536

 neighbor 192.168.1.2 remote-as 65536

 neighbor 192.168.2.2 remote-as 65547

 end 

In the following example, the routing domain is divided into autonomous systems using 4-byte autonomous system numbers 1.2, 1.0, and 1.14 and is identified by the confederation identifier 1.9. Neighbor 192.168.1.2 is a peer inside of the routing domain confederation. Neighbor 192.168.2.2 is a peer outside of the routing domain confederation. To external peers and routing domains, the confederation appears as a single autonomous system with the number 1.9. This example requires Cisco IOS Release 12.0(32)S12, 12.4(24)T, or Cisco IOS XE Release 2.3 where asdot notation is the only format for 4-byte autonomous system numbers. This configuration can also be performed using Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, or later releases.

router bgp 1.14 

 bgp confederation identifier 1.9

 bgp confederation peers 1.2 1.0 1.14

 neighbor 192.168.1.2 remote-as 1.0

 neighbor 192.168.2.2 remote-as 1.11

 end 

Related Commands

Command	Description
bgp asnotation dot	Changes the default display and the regular expression match format of BGP 4-byte autonomous system numbers from asplain (decimal values) to dot notation.
bgp confederation identifier	Specifies a BGP confederation identifier.
router bgp	Configures the BGP routing process.

Files:
Topology
Configs
BGP Configuration

BGP Large Scale BGP Route Reflectors with Clusters

BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP)- Part II

           - Larger scale BGP designs cannot be serviced by only a single RR

• Single RR is a single point of failure

           - RR "clusters" allow redundancy and hierarchy

• Cluster is defined by the clients a RR serves

• RRs in the same cluster use the same Cluster-ID

           - Inter-Cluster peerings between RRs can be client or non-client peerings

• Depends on redundancy design

Video Demonstration

from: Cisco IOS IP Routing: BGP Command Reference

bgp cluster-id

To configure the cluster ID if the BGP cluster has more than one route reflector, use the bgp cluster-id command in router configuration mode. To remove the cluster ID, use the no form of this command.

bgp cluster-id cluster-id

no bgp cluster-id cluster-id

Syntax Description

cluster-id

Cluster ID of this router acting as a route reflector; maximum of 4 bytes.

Defaults

The router ID of the single route reflector in a cluster

Command Modes

Router configuration

Command History

Release	Modification
11.0	This command was introduced.

Usage Guidelines

Together, a route reflector and its clients form a cluster.

Usually a cluster of clients will have a single route reflector. In that case, the cluster is identified by the router ID of the route reflector. In order to increase redundancy and avoid a single point of failure, a cluster might have more than one route reflector. In this case, all route reflectors in the cluster must be configured with the 4-byte cluster ID so that a route reflector can recognize updates from route reflectors in the same cluster.

If the cluster has more than one route reflector, use this command to configure the cluster ID.

Examples

In the following example, the local router is one of the route reflectors serving the cluster. It is configured with the cluster ID to identify the cluster.

router bgp 5

 neighbor 198.92.70.24 route-reflector-client

 bgp cluster-id 50000

Related Commands

Command	Description
bgp client-to-client reflection	Restores route reflection from a BGP route reflector to clients.
neighbor route-reflector-client	Configures the router as a BGP route reflector and configures the specified neighbor as its client.
show ip bgp	Displays entries in the BGP routing table.

Files:
Topology
Configs
BGP Configuration