All routing protocols employ some a type of summarization. RIP and IGRP automatically summarize at the
NIC or natural class boundary as the subnet mask is not sent in the routing updates. When a routing update
is received, the router checks if it has an interface in the same class network. If it has one, it applies the mask
configured on the interface to the incoming routing update. With no interface configured in the same NIC
network, there is insufficient information and the routing protocol uses the first octet rule to determine the
default subnet mask for the routing update.