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Configuring EIGRP
EIGRP Configuration Task List
IPC-263
Cisco IOS IP Configuration Guide
Route summarization works in conjunction with the ip summary-address eigrp interface configuration
command, in which additional summarization can be performed. If automatic summarization is in effect,
there usually is no need to configure network level summaries using the ip summary-address eigrp
command.
Configuring Summary Aggregate Addresses
You can configure a summary aggregate address for a specified interface. If any more specific routes are
in the routing table, EIGRP will advertise the summary address out the interface with a metric equal to
the minimum of all more specific routes.
To configure a summary aggregate address, use the following command in interface configuration mode:
See the “Route Summarization Example” at the end of this chapter for an example of summarizing
aggregate addresses.
Configuring Floating Summary Routes
You can also use a floating summary route when configuring the ip summary-address eigrp command.
This enhancement was introduced in Cisco IOS Release 12.2. The floating summary route is created by
applying a default route and administrative distance at the interface level. The following scenarios
illustrates the behavior of this enhancement.
Figure 46 shows a network with three routers, Router-A, Router-B, and Router-C. Router-A learns a
default route from elsewhere in the network and then advertises this route to Router-B. Router-B is
configured so that only a default summary route is advertised to Router-C. The default summary route
is applied to interface 0/1 on Router-B with the following configuration:
Router(config)# interface Serial 0/1
Router(config-if)# ip summary-address eigrp 100 0.0.0.0 0.0.0.0
Command Purpose
Router(config-router)# no auto-summary
Disables automatic summarization.
Command Purpose
Router(config-if)# ip summary-address eigrp
autonomous-system-number ip-address mask
Configures a summary aggregate address.