to identify the protocol-related information. For example, it can be used to differentiate AS
numbers carried in BGP routes imported by OSPF.
By default, the cost of the external routes imported by OSPF is 1; a maximum of 2147483647
routes can be imported each time; the type of the imported external routes is Type 2; the default
tag value of the imported routes is 1.
NOTE
You can run one of the following commands to set the cost of the imported route. The following commands
are listed in descending order of priorities.
l
Run the
apply cost
command to set the cost of a route.
l
Run the
import-route
command to set the cost of the imported route.
l
Run the
default
command to set the default cost of the imported route.
Step 5
(Optional) Run:
filter-policy
{
acl-number
|
acl-nameacl-name
|
ip-prefixip-prefix-name
}
export
[
protocol
[
process-id
] ]
can be advertised only when meeting filtering conditions.
OSPF filters the imported routes. OSPF uses Type 5 LSAs to carry routes that meet the filtering
conditions and advertises these Type 5 LSAs.
You can specify the parameter
protocol
[
process-id
] to filter the routes of a certain routing
protocol or a certain OSPF process. If
protocol
[
process-id
] is not specified, OSPF filters all
imported routes.
The
import-route
command cannot be used to import the default route from another AS.
----End
4.6.3 Configuring OSPF to Import a Default Route
The default route is widely applied on the OSPF network to reduce routing entries in the routing
table and filter specific routing information.
Context
On the area border and AS border of an OSPF network generally reside multiple switches for
next-hop backup or traffic load balancing. A default route can be configured to reduce routing
entries and improve resource usage on the OSPF network.
The default route is generally applied to the following scenarios:
1.
An ABR in an area advertises Type 3 LSAs carrying the default route within the area.
switches in the area use the received default route to forward inter-area packets.
2.
An ASBR in an AS advertises Type 5 or Type 7 LSAs carrying the default route within the
AS. switches in the AS use the received default route to forward AS external packets.
When no exactly matched route is discovered, the switch can forward packets through the default
route.
The preference of the default route in Type 3 LSAs is higher than that of the route in Type 5 or
Type 7 LSAs.
The advertising mode of the default route is determined by the type of the area to which the
default route is imported, as shown in
.
S6700 Series Ethernet Switches
Configuration Guide - IP Routing
4 OSPF Configuration
Issue 01 (2012-03-15)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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