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CCNA3 (Chapter9)

Terms in this set (13)

Which two types of LSAs are flooded only within the area in which they originated? (Choose two.)
1. type1
2. type2

Refer to curriculum topic: 9.1.2
Type 1 and type 2 LSAs are intra-area LSAs and are not propagated to other areas. Type 3 and 4 LSAs are flooded from one area to another by ABRs. Type 5 LSAs are flooded by ASBRs throughout the entire OSPF domain.
An OSPF router has received type 3 summary LSAs that were flooded into an area. How are these LSAs identified in the routing table?
O IA

Refer to curriculum topic: 9.1.3
ABRs flood type 3 summary LSAs into areas to advertise networks reachable in other areas. These type 3 LSAs appear in the routing table with an O IA, interarea descriptor.
Match the OSPF LSA types to their descriptions. (Not all options are used.)
LSA type 1: including a list of directly attach network prefix and link type
LSA type 2: identifying the routers and the network address of the multi access links
LSA type 3: advertising networks from other areas ABRs
LSA type 4: advertising an ASBR to other areas and providing a routes to it
LSA type 5: advertising external(non-OSPF) network address
B

Refer to curriculum topic: 9.1.2
OSPF uses link-state advertisement messages (LSAs) to build the LSDB and maintain routing tables. OSPF routers use LSA types 1 to 5 to describe the networks to which they are directly connected or networks which they learned from other routers. These networks can be located in other areas or can also be from non-OSPF networks. Some LSAs are used to identify an ASBR. While most LSAs will be flooded across multiple areas, some LSAs are flooded only within the area where they originated.
Which LSA type advertises directly connected OSPF-enabled links to other OSPF routers within the OSPF area they originated?
type1

o curriculum topic: 9.1.2
Type 1 LSAs contain information about OSPF enabled links on a router and are flooded through an area to other OSPF routers. The information included in this type of LSA includes a list of the directly connected interfaces, link types, neighbors, and link states of the OSPF interfaces of the router.
Refer to the exhibit. A network administrator is configuring OSPFv2 on R1. Which conclusion can be drawn based on the configuration?
R1 is an ABR

Refer to curriculum topic: 9.2.1
R1 is joining two areas, area 0 and area 1, so it is an ABR. The OSPF process number could be any number and it does not indicate how many OSPF processes are running. Because 192.168.10.0 0.0.0.7 means a prefix length of /29, there are 8 total but 6 valid addresses for hosts. Therefore, area 0 could have up to 6 routers. R1 is advertising 2 separate noncontiguous networks from area 1.
Refer to the exhibit. A network administrator is configuring OSPFv3 on R1. Which command sequence is used to advertise the network that is attached to Gi0/0?
R1(config)# interface GigabitEthernet 0/0
R1(config-if)# ipv6 ospf 3 area 1

Refer to curriculum topic: 9.2.1
Different from OSPFv2, OSPFv3 does not specify networks to be advertised under the router configuration mode. OSPFv3 enables a network to be in OSPFv3 with the command ipv6 ospf area under the interface configuration mode.
Which two statements describe OSPF? (Choose two.)
1. OSPF routers within an area have the same link-state information.
2. OSPF routers may have large routing tables if routes are not summarized.

Refer to curriculum topic: 9.1.1
OSPF routers within the same area will have the same link-state databases. Without route summarization, OSPF routers may have large routing tables. There is no automatic summarization of routes with OSPF. OSPF can be implemented in a single area or in a two-layer multiarea hierarchy. SPF recalculation, especially in larger networks, is processor intensive.
What information is advertised in a type 4 LSA?
the route to reach an ASBR

Refer to curriculum topic: 9.1.2
The type 4 LSA is generated by an ABR to advertise to other OSPF routers the presence of an ASBR and the route used to reach the ASBR.
An ABR in a multiarea OSPF network receives LSAs from its neighbor that identify the neighbor as an ASBR with learned external networks from the Internet. Which LSA type would the ABR send to other areas to identify the ASBR, so that internal traffic that is destined for the Internet will be sent through the ASBR?
LSA type4

Refer to curriculum topic: 9.1.2
An OSPF type 4 summary LSA is generated by an ABR only when an ASBR exists within an area. A type 4 LSA identifies the ASBR and provides a route to it so the routing table will have an entry for traffic that is destined for the external autonomous network.
What must all non-backbone OSPF areas connect to when deploying multiarea OSPF?
Area 0

Refer to curriculum topic: 9.1.1
All non-backbone areas must be attached to Area 0, which is the backbone area, in multiarea OSPF. The backbone area interconnects non-backbone areas.
Which type of routing table entry would indicate that an external route was redistributed into the multiarea OSPF process?
O E2

Refer to curriculum topic: 9.1.3
An O routing table entry indicates a route, from within the same area, that was learned through OSPF updates. An O IA route is a route from another OSPF area. An O E2 or O E1 route is an external route, such as one redistributed from RIP, EIGRP, or a static route, that was redistributed into the OSPF process. An S entry is for a static route. A C entry represents a directly connected network.
Which LSA type is flooded by a designated router to other OSPF routers within the same area?
type2

Refer to curriculum topic: 9.1.2
Type 2 LSAs are flooded by the DR to inform other OSPF routers about multiaccess networks within an area
What is a benefit of multiarea OSPF routing?
Topology changes in one area do not cause SPF recalculations in other areas.

Refer to curriculum topic: 9.1.1
With multiarea OSPF, only routers within an area share the same link-state database. Changes to the network topology in one area do not impact other areas, which reduces the number of SPF algorithm calculations and the size of link-state databases.
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