Configuring Ospf Area Parameters; Prerequisites; Configuration Procedure - 3Com MSR 50 Series Configuration Manual

940 C 58: OSPF C
HAPTER
Configuring OSPF
Area Parameters

Prerequisites

Configuration Procedure

ONFIGURATION
n
An OSPF process ID is unique, including the process ID for OSPF multi-instance,
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which cannot be the same as any previously configured ID.
A network segment can only belong to one area.
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It is recommended to configure a description for each OSPF process to help
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identify purposes of processes and for ease of management and memorization.
It is recommended to configure a description for each area to help identify
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purposes of areas and for ease of management and memorization.
Splitting an OSPF AS into multiple areas reduces the number of LSAs on networks
and extends OSPF application. For those non-backbone areas residing on the AS
boundary, you can configure them as Stub areas to further reduce the size of
routing tables on routers in these areas and the number of LSAs.
A stub area cannot redistribute routes, thus introducing the concept of NSSA,
where type 7 LSAs (NSSA External LSAs) are advertised. Type 7 LSAs originate from
the ASBR in a NSSA area. When arriving at the ABR in the NSSA area, these LSAs
will be translated into type 5 LSAs for advertisement to other areas.
Non-backbone areas exchange routing information via the backbone area.
Therefore, the backbone and non-backbone areas, including the backbone itself
must maintain connectivity.
If necessary physical links are not available for this connectivity maintenance, you
can configure virtual links to solve it.
Before configuring an OSPF area, you have configured:
IP addresses for interfaces, making neighboring nodes accessible with each
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other at network layer.
OSPF basic functions
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Follow these steps to configure OSPF area parameters:
To do...
Enter system view
Enter OSPF view
Enter area view
Configure the area as a stub
area
Configure the area as an
NSSA area
Specify a cost for the default
route advertised to the stub or
NSSA area
Use the command...
system-view
ospf [ process-id | router-id
router-id | vpn-instance
instance-name ] *
area area-id
stub [ no-summary ]
nssa
[ default-route-advertise |
no-import-route |
no-summary ] *
default-cost cost
Remarks
-
-
Required
Optional
Not configured by default
Optional
Not configured by default
Optional
Defaults to 1