3com 3031 Instruccion De Instalación

will still send hello messages to its neighbor with preference level 0, to set up 
adjacency relation. 

The dynamic routing protocols on the router can share the routing information. As 
far as OSPF is concerned, the routes discovered by other routing protocols are 
always processed as the external routes of AS. In the 

 commands, 

you can specify the route cost type, cost and tag to overwrite the default route 
receipt parameters (refer to “Configuring Parameters for OSPF to Import External 
Routes”).

The OSPF uses the following four types of routes (sequencing in priority):

■

Intra-area route

■

Inter-area route

■

External route type 1

■

External route type 2

Intra-area and inter-area routes describe the internal AS topology whereas the 
external routes describe how to select the route to the destinations beyond the 
AS.

The external routes type-1 refers to the imported IGP routes (such as static route 
and RIP). Since these routes are more reliable, the calculated cost of the external 
routes is the same as the cost of routes within the AS. Also, such route cost and 
the route cost of the OSPF itself are comparable. That is, cost to reach the external 
route type 1 = cost to reach the corresponding ASBR from the local router + cost 
to reach the destination address of the route from the ASBR.

The external routes type-2 refers to the imported EGP routes. Since these routes 
have lower credibility, OSPF assumes that the cost spent from the ASBR to reach 
the destinations beyond the AS is greatly higher than that spent from within the 
AS to the ASBR. So in route cost calculation, the former is mainly considered, that 
is, the cost spent to reach the external route type 2 = cost spent to the destination 
address of the route from the ASBR. If the two values are equal, then the cost of 
the router to the corresponding ASBR will be considered.

Perform the following in the OSPF View.

By default, OSPF will not import the routing information of other protocols.

The 

 specifies a source routing protocol that can be imported. By far, it 

can be Direct, Static, RIP, IS-IS or BGP.

Table 567   Configuring OSPF to Import Routes of Other Protocols

Configure OSPF to import routes of 
other protocols

import-route protocol [ cost value ] [ 
type { 1 | 2 } ] [ tag value ] [ 
route-policy route-policy-name ]

Cancel importing routing 
information of other protocols

undo import-route protocol