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Chapter 6
Troubleshooting TCP/IP Connectivity
Multiple router types can exist within an OSPF area. Table 6.10 lists all
of the OSPF router types and the role that each plays within the area.
In addition to the previous responsibilities, a router can also be assigned
additional responsibilities. These additions are assumed when a router is
assigned the role of DR or BDR.
show Commands
Due to the complexity of OSPF, several show commands are available to pro-
vide information regarding the configuration and functionality of OSPF on a
router. Table 6.11 lists most of the available OSPF-related show commands.
T A B L E 6 . 1 0
OSPF Router Types
Router Type
Description of Responsibility
Internal
All interfaces are defined on the same area. All internal
routers have an identical link-state database.
Backbone
Has at least one interface assigned to area 0.
Area Border
Router (ABR)
Interfaces are connected to multiple OSPF areas. Infor-
mation specific to each area is stored on this type of
router.
Autonomous
System Border
Router (ASBR)
This type of router has an interface connected to an ex-
ternal network or a different AS.
T A B L E 6 . 1 1
OSPF show Commands
Command
Description / Output
show running-config
Displays the current router configuration.
show ip route
Displays the entire IP route table.
show ip route ospf
Displays OSPF routes.
show ip ospf
Displays information for OSPF.
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