Hitachi GR2000 Series Installation Manual page 271

When you replace the existing router (other than GR2000) with this router, pay
attention to possible deviation of RIP-1 implementation. For example, the followin
routers have different implementations of RIP-1: Hitachi's NP200, NP150, NP100
NP120C, and Cisco Systems' routers.
When an interface address is further divided into subnets, GR2000 does not crea
natural mask route (network route for the subject interface). Instead, it creates a
subnet route with broadcast connection and a host route with point-to-point
connection. Since RIP-1 does not advertise a subnet route that exceeds the
addressing boundary, aggregation specifying with the configuration definition is
required on GR2000.
A different implementation of RIP-1 may automatically aggregate subnet routes t
network route, and an aggregated route is usually not registered in the forwardin
table. On GR2000, the aggregated route is by default registered in the forwarding
table as the active route.
In order to attain compatible operation on GR2000 with such a device with differ
RIP-1 implementation, the option setting is required for the definit
noinstall aggregate
in the configuration information. Figure 4-12 illustrates a sample network
configuration requiring the option setting.
noinstall