Hitachi GR2000 Series Installation Manual page 268

When you connect GR2000 with devices other than GR2000 based on the IP routing,
pay attention to the following.
4.7.1 Interface Address in Point-to-Point Line Connection
GR2000 regards the route information in the point-to-point line connection (direct
connection) as two host routes. This method is also adopted in Hitachi routers
NP220, NP200, and NP150. Accordingly, when a network only consists of these
routing devices, you can assign interface addresses to the point-to-point line as
follows. Be careful not to use this method with any other routing device.
You can assign the same network IP address or subnetwork IP address to
multiple point-to-point lines.
You can assign two different network IP addresses or subnetwork IP addresses to
both ends of a point-to-point line.
Note: Although GR2000 treats the route information of a point-to-point line as two host
*
routes, Cisco Systems' routers treat such information as one network route. This
causes a discrepancy in the route information advertised by the routing protocol.