Cisco 500 Series, Руководство по настройке

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9-13
Cisco Security Appliance Command Line Configuration Guide
OL-12172-03
Chapter 9 Configuring IP Routing
Configuring OSPF
Configuring OSPF Area Parameters
You can configure several area parameters. These area parameters (shown in the following task table)
include setting authentication, defining stub areas, and assigning specific costs to the default summary
route. Authentication provides password-based protection against unauthorized access to an area.
Stub areas are areas into which information on external routes is not sent. Instead, there is a default
external route generated by the ABR, into the stub area for destinations outside the autonomous system.
To take advantage of the OSPF stub area support, default routing must be used in the stub area. To further
reduce the number of LSAs sent into a stub area, you can configure the
no-summary keyword of the
area stub command on the ABR to prevent it from sending summary link advertisement (LSA Type 3)
into the stub area.
To specify area parameters for your network, perform the following steps:
Step 1 If you have not already done so, enter the router configuration mode for the OSPF process you want to
configure by entering the following command:
hostname(config)# router ospf process_id
Step 2
Enter any of the following commands:
• To enable authentication for an OSPF area, enter the following command:
hostname(config-router)# area area-id authentication
•
To enable MD5 authentication for an OSPF area, enter the following command:
hostname(config-router)#
area
area-id
authentication message-digest
• To define an area to be a stub area, enter the following command:
hostname(config-router)# area area-id stub [ no-summary ]
•
To assign a specific cost to the default summary route used for the stub area, enter the following
command:
hostname(config-router)# area area-id default-cost cost
The cost is an integer from 1 to 65535. The default is 1.
The following example shows how to configure the OSPF area parameters:
hostname(config)# router ospf 2
hostname(config-router)# area 0 authentication
hostname(config-router)# area 0 authentication message-digest
hostname(config-router)# area 17 stub
hostname(config-router)# area 17 default-cost 20
Configuring OSPF NSSA
The OSPF implementation of an NSSA is similar to an OSPF stub area. NSSA does not flood type 5
external LSAs from the core into the area, but it can import autonomous system external routes in a
limited way within the area.