3.4 OSPFv2 Flashcards
Configure and verify single area OSPFv2, including neighbor adjacencies, point-to-point, broadcast, and router ID. (24 cards)
Which routing protocol is classified as a link-state protocol?
OSPF
(Open Shortest Path First)
OSPF is a link-state protocol that efficiently shares routing information using LSAs (Link-State Advertisements), helping routers to dynamically update and adjust their routing tables.
What occurs when a designated router (DR) fails in OSPF?
The backup designated router (BDR) takes over as the new DR.
This transition ensures continued stability in OSPF routing operations when the primary DR is unavailable.
What three conditions must routers meet to achieve a two-way OSPF state?
- They must verify that Hello parameters match.
- They must exchange Hello packets.
- They must have matching subnet masks and authentication settings.
Achieving a two-way state is essential for routers to establish a connection before moving to full adjacency in OSPF.
What are the two multicast addresses used for DR/BDR communication in OSPF?
- 224.0.0.5
- 224.0.0.6
The address 224.0.0.5 is designated for all OSPF routers, while 224.0.0.6 is specifically for SPF designated routers, facilitating efficient OSPF message exchanges.
List four types of information that is displayed from the ‘show ip ospf neighbor’ command.
- State
- Neighbor ID
- Interface
- Address
The command provides crucial details about OSPF neighbors, while other information such as Link ID and Age is found in the ‘show ip ospf database’ command.
What does the state ‘FULL/BDR’ indicate about an OSPF neighbor?
The neighbor is fully adjacent and acts as the BDR.
In OSPF, a FULL/BDR state means the neighbor has established full adjacency while being the backup to the designated router.
List two true statements regarding OSPF neighbor states.
- OSPF routers on the same link that match Hello parameters are considered neighbors.
- A designated router reaches full adjacency with all its neighbors.
**Neighbor relationships are foundational in OSPF, allowing routers to communicate and establish routing paths.
How is a router ID configured in OSPF?
Using the command:** router-id [ID]**.
This configuration is optional but important for OSPF routing operations.
If the ‘Nbrs F/C’ column displays 3/4 in ‘show ip ospf interface brief’, how many neighbors are not fully adjacent?
1
This indicates that out of four neighbors, three have achieved full adjacency, leaving one in a different state.
List two facts about router IDs in OSPF that are correct.
- A router with a higher router ID wins in case of a tie during DR/BDR elections.
- The router ID is configured using the ‘router-id’ command.
Router IDs are crucial in OSPF for determining the designated router and backup designated router.
True or False:
The neighbor relationship state on a point-to-point OSPF interface as seen in ‘show ip ospf neighbor’ output is FULL/ -.
True
In point-to-point connections, there is no designated router or backup designated router, resulting in a dash in the output.
What three conditions must be met for OSPF routers to become neighbors?
- Connected to the same serial link.
- Connected to the same Ethernet WAN link.
- Connected to the same VLAN.
Router adjacency in OSPF requires that routers share the same data link for effective communication.
True or False:
The number in the command ‘router OSPF 1’ signifies the OSPF process ID.
True
The process ID is a locally significant identifier used by the router to manage and distinguish between multiple OSPF processes running on the device.
What two statements accurately describe the roles of DR and BDR in OSPF?
- The designated router (DR) is responsible for distributing routing information to other routers.
- The backup designated router (BDR) assumes the DR’s role if it fails.
DR and BDR are essential for maintaining efficient communication and routing updates in OSPF networks.
What role does the designated router (DR) play in OSPF?
The DR distributes Link State Advertisements (LSAs) to other routers.
The DR ensures that all routers on the same subnet maintain consistent copies of each LSA, preventing unnecessary flooding of LSAs across the network.
Fill in the blank:
OSPF does not elect DR/BDR roles on ______ ______.
point-to-point links
In point-to-point connections, all routers can communicate directly, eliminating the need for a DR or BDR.
Which command can be used to check if two routers are OSPF neighbors?
show ip ospf neighbor
This command provides a list of OSPF neighbors and their states, helping to verify OSPF adjacency.
What command initiates the OSPF routing process on a router?
router ospf 1
This command starts OSPF with a specified process ID, allowing for OSPF routing to commence on the router.
What are the two key factors in the DR/BDR election process?
- Router ID
- Interface priority
The election prioritizes the highest interface priority first, and if there is a tie, the router with the highest router ID is selected.
Which command enables OSPF on both G0/1/0 and G0/2/0 interfaces with the given IP addresses?
network 10.0.0.0 0.255.255.255 area 0
This command matches the interfaces based on the specified network address and wildcard mask, allowing OSPF to be enabled on the relevant interfaces.
How can you check the priority of an interface for DR/BDR elections?
show ip ospf interfaces
This command displays the priority values of interfaces, which are crucial for determining the outcome of DR and BDR elections.
Which command shows the DR and BDR roles of router interfaces?
show ip ospf interface brief
This command summarizes the state of each interface, including its role in the OSPF process, providing a quick overview of DR and BDR assignments.
What wildcard mask matches the first three octets in the network command?
0.0.0.255
In this wildcard mask, zeros indicate that the corresponding octets must match exactly, while the 255 allows for flexibility in the last octet.
Which command configures OSPF for a point-to-point Ethernet WAN?
ip ospf network point-to-point
This command optimizes OSPF operation on point-to-point links by reducing unnecessary overhead associated with broadcast networks.
