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| 5.5 |  | Configuring EIGRP |
| 5.5.4 |  | Summarizing EIGRP Routes: no auto-summary |

EIGRP automatically summarizes routes at the classful boundary, the boundary where the network address ends as defined by class-based addressing. This means that even though RTC is connected only to the subnet 2.1.1.0, it will advertise that it is connected to the entire Class A network, 2.0.0.0. In most cases, auto summarization is a good thing, keeping the routing tables as compact as possible.

In the presence of discontiguous subnetworks, automatic summarization must be disabled for routing to work properly. To turn off auto-summarization, use the following command:

> Router(config-router)#no auto-summary