Answers to Review Questions
B. The definition of an internal router is a router that has all of its
interfaces within the same OSPF area. Keep in mind that a router can
fall into multiple categories. For example, if an internal router is in
Area 0, it would also be considered a backbone router.
B. The routing table of area border routers can be shown using the
IOS command show ip ospf border-routers. This table shows
which border router will get a packet to the network.
B and C. The concept of an OSPF totally stubby area is specific to
Cisco routers. In addition to not receiving Type 5 LSAs as a stub area
does, a totally stubby area does not receive summary Link State
B and C. The backbone area cannot be a stub area. Also, only rout-
ers configured as stubby will be able to form adjacencies within a
D. The syntax for creating a virtual link is area area-id virtual-
, where area-id is the number of the transit area
and where router-id is the IP address of the highest loopback inter-
face configured on a router. If a loopback is not configured, then the
is the highest IP address configured on the router.
C. The IOS command show ip ospf neighbor shows neighbor
router information, such as Neighbor ID and the state of adjacency
with the neighboring router.
A, B, and C. Both Type 3 LSAs and Type 4 LSAs are considered to be
Summary Link Advertisements. While totally stubby areas do not
receive Summary Link Advertisements, stub areas do.
A. A backbone router has at least one of its interfaces connected to
OSPF Area 0.
B. The command
summary-address network-address network-
is used on an autonomous system boundary router (ASBR) to
summarize external routes before they are injected into OSPF.
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