Types Of Ospf Routing Devices - IBM RackSwitch G8000 Application Manual

ABR
Internal LSA
Routes
Not-So-Stubby Area
(NSSA)
External LSA
Routes
Non-OSPF Area
RIP/BGP AS

Types of OSPF Routing Devices

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RackSwitch G8000: Application Guide
Figure 26. OSPF Area Types
(Also a Transit Area)
No External Routes
ASBR
ABR = Area Border Router
ASBR = Autonomous System
As shown in Figure 27, OSPF uses the following types of routing devices:
• Internal Router (IR)—a router that has all of its interfaces within the same area.
IRs maintain LSDBs identical to those of other routing devices within the local
area.
• Area Border Router (ABR)—a router that has interfaces in multiple areas. ABRs
maintain one LSDB for each connected area and disseminate routing information
between areas.
• Autonomous System Boundary Router (ASBR)—a router that acts as a gateway
between the OSPF domain and non-OSPF domains, such as RIP, BGP, and
static routes.
Figure 27. OSPF Domain and an Autonomous System
BGP
External
ASBR
Routes
RIP
ASBR
Backbone
Area 0
ABR
Stub Area
from Backbone
Boundary Router
OSPF Autonomous System
Backbone
Area 0
Inter-Area Routes
(Summary Routes)
ABR
Area 1
ABR
Virtual
Link
Transit Area
ABR
Stub Area, NSSA,
or Transit Area
Connected to Backbone
via Virtual Link
Area 3
ABR
ABR
Internal
Router
Area 2