EIGRP Auto-Summary Now Disabled By Default

Directly from Cisco,s EIGRP command ref guide:

auto-summary (EIGRP)

To allow automatic summarization of subnet routes into network-level routes, use the auto-summary command in router configuration mode or address-family topology configuration mode. To disable this function and send subprefix routing information across classful network boundaries, use the no form of this command.

auto-summary

no auto-summary

Syntax Description

This command has no arguments or keywords.

Command Default

The behavior of this command is enabled by default (the software does not send subprefix routing information across classful network boundaries).

Cisco IOS Release 15.0(1)M, 12.2(33)SRE, 12.2(33)XNE, Cisco IOS XE Release 2.5, Cisco IOS Release 12.2(33)SXI4 and Later Releases

The behavior of this command is disabled by default (the software sends subprefix routing information across classful network boundaries).

Command Modes

Router configuration (config-router)
Address-family topology configuration (config-router-af-topology)

Command History

Release	Modification
10.0	This command was introduced.
12.2(8)T	The command default behavior changed to disabled.
12.2(33)SRA	This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX	This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.
15.0(1)M	This command was modified. Address-family topology configuration mode was added. The default behavior was changed to disabled.
12.2(33)SRE	This command was modified. Address-family topology configuration mode was added. The default behavior was changed to disabled.
12.2(33)XNE	This command was integrated into Cisco IOS Release 12.2(33)XNE.
Cisco IOS XE Release 2.5	This command was integrated into Cisco IOS XE Release 2.5.
12.2(33)SXI4	This command was modified. Address-family topology configuration mode was added. The default behavior was changed to disabled.

Usage Guidelines

To allow the software to create summary subprefixes to the classful network boundary when crossing classful network boundaries, use the auto-summary command.

Enhanced Interior Gateway Routing Protocol (EIGRP) summary routes are given an administrative distance value of 5. You cannot configure this value.

Examples

The following example enables automatic summarization for EIGRP process 109:

Router(config)# router eigrp 109

Router(config-router)# auto-summary

The following example enables automatic summarization for EIGRP autonomous-system 4473:

Router(config)# router eigrp virtual-name 

Router(config-router)# address-family ipv4 autonomous-system 4473

Router(config-router-af)# topology base 

Router(config-router-af-topology)# auto-summary 

Related Commands

Command	Description
address-family (EIGRP)	Enters address-family configuration mode to configure an EIGRP routing instance.
ip summary-address eigrp	Configures a summary aggregate address for a specified interface.
router eigrp	Configures the EIGRP address-family process.
topology (EIGRP)	Configures an EIGRP process to route IP traffic under the specified topology instance and enters router address-family topology configuration mode.