The Enhanced Interior Gateway Routing Protocol (EIGRP) can be configured using either the classic mode or the named mode. The classic mode is the old way of configuring EIGRP. In classic mode, EIGRP configurations are scattered across the router mode and the interface mode. The named mode is the new way of configuring EIGRP; this mode allows EIGRP configurations to be entered in a hierarchical manner under the router mode.
Each named mode configuration can have multiple address families and autonomous system number combinations. In the named mode, you can have similar configurations across IPv4 and IPv6. We recommend that you upgrade to EIGRP named mode because all new features, such as Wide Metrics, IPv6 VRF Lite, and EIGRP Route Tag Enhancements, are available only in EIGRP named mode.
Use the eigrp upgrade-cli command to upgrade from classic mode to named mode. You must use the eigrp upgrade-cli command for all classic router configurations to ensure that these configurations are upgraded to the named mode. Therefore, if multiple classic configurations exist, you must use this command per autonomous system number. You must use this command separately for IPv4 and IPv6 configurations.
Prior to the EIGRP Classic to Named Mode Conversion feature, upgrading to EIGRP named mode required that the user manually unconfigure the classic mode using the no router eigrp autonomous-system-number command and then reconfigure EIGRP configurations under named mode using the router eigrp virtual name command. This method may lead to network churn and neighborship or network flaps.
The EIGRP Classic to Named Mode Conversion feature allows you to convert from classic mode to named mode without causing network flaps or the EIGRP process to restart. With this feature, you can move an entire classic mode configuration to a router named mode configuration, and consequently, all configurations under interfaces will be moved to the address-family interface under the appropriate address family and autonomous-system number. After conversion, the show running-config command will show only named mode configurations; you will not see any old classic mode configurations.