©PREP4EXAMS@2024 [REAL EXAM DUMPS] Thursday, July 18, 2024 5:35 PM
OSPF Exam Practice Questions and
Answers (100% Pass)
What type of routing protocol is OSPF? - ✔️✔️OSPF is a link state routing protocol.
POP QUIZ: How frequently does OSPF send out routing updates? - ✔️✔️OSPF sends out routing
updates every 30 minutes, and refreshes the LSDB for neighbor adjacencies.
POP QUIZ: How long does OSPF wait before considering a route previously learned, dead? -
✔️✔️The MaxAge timer is set to 60 minutes.
MaxAge is always 1 hour, and it has to be 1 hour on all platforms. The reason why is that
MaxAge is a special value that's used to flush a route out of the OSPF database.
For example if I have a connected link that's advertised into OSPF, and the link goes down, to
withdraw the link from other routers I re-flood it with MaxAge.
This is why the value has to be the same everywhere otherwise the routers couldn't properly
remove a route from the database.
What are the three main branches that can be broken down from link state routing protocol logic?
- ✔️✔️You have
1. Neighbor discovery (neighbor table)
1
,©PREP4EXAMS@2024 [REAL EXAM DUMPS] Thursday, July 18, 2024 5:35 PM
2. Topology database exchange (topology table)
3. Route computation (routing table)
What multicast address are OSPF hello packets sent to? - ✔️✔️224.0.0.5
POP QUIZ: OSPF uses TCP/UDP for its transport protocol. T/F? - ✔️✔️F.
It uses IP protocol 89.
What concept does OSPF use to segment LSDB flooding? - ✔️✔️OSPF uses the concept of
"Area's" to segment LSDB flooding between peers.
How does OSPF decide upon its RID? - ✔️✔️It's the exact same as EIGRP.
It checks to see if you:
1. Manually configured (first)
2. Highest IP address of an up/up Loopback interface
3. The highest IP address of any up/up non-loopback (physical) inteface
What do you have to do after changing the OSPF RID to take effect? - ✔️✔️You need to either run
the `reload` or `clear ip ospf process` command.
It's an intrusive change, and will prompt you with a warning message before proceeding.
This is because it will tear down the OSPF neighbor relationship, and cause all links within that
area to recalculate their SPF tree.
How many OSPF neighbor states are there? - ✔️✔️8
2
,©PREP4EXAMS@2024 [REAL EXAM DUMPS] Thursday, July 18, 2024 5:35 PM
What are those 8 OSPF neighbor states? - ✔️✔️Down
Attempt
Init
2-Way
Exstart
Exchange
Loading
Full
What is the purpose of each OSPF neighbor state? - ✔️✔️Down:
This is the first OSPF neighbor state. It means that no information (hellos) has been received
from this neighbor, but hello packets can still be sent to the neighbor in this state.
During the fully adjacent neighbor state, if a router doesn't receive hello packet from a neighbor
within the RouterDeadInterval time (RouterDeadInterval = 4*HelloInterval by default) or if the
manually configured neighbor is being removed from the configuration, then the neighbor state
changes from Full to Down.
Attempt:
This state is only valid for manually configured neighbors in an NBMA environment. In Attempt
state, the router sends unicast hello packets every poll interval to the neighbor, from which hellos
have not been received within the dead interval.
3
, ©PREP4EXAMS@2024 [REAL EXAM DUMPS] Thursday, July 18, 2024 5:35 PM
Init:
This state specifies that the router has received a hello packet from its neighbor, but the receiving
router's ID was not included in the hello packet. When a router receives a hello packet from a
neighbor, it should list the sender's router ID in its hello packet as an acknowledgment that it
received a valid hello packet.
2-Way:
This state designates that bi-directional communication has been established between two
routers. Bi-directional means that each router has seen the other's hello packet. This state is
attained when the router receiving the hello packet sees its own Router ID within the received
hello packet's neighbor field. At this state, a router decides whether to become adjacent with this
neighbor. On broadcast media and non-broadcast multiaccess networks, a router becomes full
only with the designated router (DR) and the backup designated router (BDR); it stays in the 2-
way state with all other neighbors. On Point-to-point and Point-to-multipoint networks, a router
becomes full with all connected routers.
At the end of this stage, the DR and BDR
What does OSPF use to describe each neighbor state? - ✔️✔️OSPF uses it's underlying finite state
machine (FSM) to represent its state changes.
What IP address does OSPF send multicast traffic to? - ✔️✔️224.0.0.5
4
OSPF Exam Practice Questions and
Answers (100% Pass)
What type of routing protocol is OSPF? - ✔️✔️OSPF is a link state routing protocol.
POP QUIZ: How frequently does OSPF send out routing updates? - ✔️✔️OSPF sends out routing
updates every 30 minutes, and refreshes the LSDB for neighbor adjacencies.
POP QUIZ: How long does OSPF wait before considering a route previously learned, dead? -
✔️✔️The MaxAge timer is set to 60 minutes.
MaxAge is always 1 hour, and it has to be 1 hour on all platforms. The reason why is that
MaxAge is a special value that's used to flush a route out of the OSPF database.
For example if I have a connected link that's advertised into OSPF, and the link goes down, to
withdraw the link from other routers I re-flood it with MaxAge.
This is why the value has to be the same everywhere otherwise the routers couldn't properly
remove a route from the database.
What are the three main branches that can be broken down from link state routing protocol logic?
- ✔️✔️You have
1. Neighbor discovery (neighbor table)
1
,©PREP4EXAMS@2024 [REAL EXAM DUMPS] Thursday, July 18, 2024 5:35 PM
2. Topology database exchange (topology table)
3. Route computation (routing table)
What multicast address are OSPF hello packets sent to? - ✔️✔️224.0.0.5
POP QUIZ: OSPF uses TCP/UDP for its transport protocol. T/F? - ✔️✔️F.
It uses IP protocol 89.
What concept does OSPF use to segment LSDB flooding? - ✔️✔️OSPF uses the concept of
"Area's" to segment LSDB flooding between peers.
How does OSPF decide upon its RID? - ✔️✔️It's the exact same as EIGRP.
It checks to see if you:
1. Manually configured (first)
2. Highest IP address of an up/up Loopback interface
3. The highest IP address of any up/up non-loopback (physical) inteface
What do you have to do after changing the OSPF RID to take effect? - ✔️✔️You need to either run
the `reload` or `clear ip ospf process` command.
It's an intrusive change, and will prompt you with a warning message before proceeding.
This is because it will tear down the OSPF neighbor relationship, and cause all links within that
area to recalculate their SPF tree.
How many OSPF neighbor states are there? - ✔️✔️8
2
,©PREP4EXAMS@2024 [REAL EXAM DUMPS] Thursday, July 18, 2024 5:35 PM
What are those 8 OSPF neighbor states? - ✔️✔️Down
Attempt
Init
2-Way
Exstart
Exchange
Loading
Full
What is the purpose of each OSPF neighbor state? - ✔️✔️Down:
This is the first OSPF neighbor state. It means that no information (hellos) has been received
from this neighbor, but hello packets can still be sent to the neighbor in this state.
During the fully adjacent neighbor state, if a router doesn't receive hello packet from a neighbor
within the RouterDeadInterval time (RouterDeadInterval = 4*HelloInterval by default) or if the
manually configured neighbor is being removed from the configuration, then the neighbor state
changes from Full to Down.
Attempt:
This state is only valid for manually configured neighbors in an NBMA environment. In Attempt
state, the router sends unicast hello packets every poll interval to the neighbor, from which hellos
have not been received within the dead interval.
3
, ©PREP4EXAMS@2024 [REAL EXAM DUMPS] Thursday, July 18, 2024 5:35 PM
Init:
This state specifies that the router has received a hello packet from its neighbor, but the receiving
router's ID was not included in the hello packet. When a router receives a hello packet from a
neighbor, it should list the sender's router ID in its hello packet as an acknowledgment that it
received a valid hello packet.
2-Way:
This state designates that bi-directional communication has been established between two
routers. Bi-directional means that each router has seen the other's hello packet. This state is
attained when the router receiving the hello packet sees its own Router ID within the received
hello packet's neighbor field. At this state, a router decides whether to become adjacent with this
neighbor. On broadcast media and non-broadcast multiaccess networks, a router becomes full
only with the designated router (DR) and the backup designated router (BDR); it stays in the 2-
way state with all other neighbors. On Point-to-point and Point-to-multipoint networks, a router
becomes full with all connected routers.
At the end of this stage, the DR and BDR
What does OSPF use to describe each neighbor state? - ✔️✔️OSPF uses it's underlying finite state
machine (FSM) to represent its state changes.
What IP address does OSPF send multicast traffic to? - ✔️✔️224.0.0.5
4
