Question 222 of 367 from exam 200-301-CCNA: Implementing and Administering Cisco Solutions

Question 222 of 367 from exam 200-301-CCNA: Implementing and Administering Cisco Solutions


The OSPF Hello protocol performs which of the following tasks? (Choose two.)



A. B. C. D. E. F.


Sure, I can help explain the OSPF Hello protocol and its tasks in detail.

The OSPF (Open Shortest Path First) protocol is a link-state routing protocol that uses a database of link-state advertisements (LSAs) to calculate the shortest path to a destination network. The OSPF Hello protocol is an important part of OSPF and performs several tasks, including:

  1. Dynamic neighbor discovery: OSPF Hello protocol uses multicast messages to discover other OSPF routers on the network. When a router sends a Hello packet, it includes information about itself, such as its router ID, OSPF interface IP address, and subnet mask. If a router receives a Hello packet with this information, it can add the sender as a neighbor.

  2. Maintains neighbor relationships: Once a neighbor is discovered, OSPF Hello protocol is responsible for maintaining the neighbor relationship. It does this by periodically sending Hello packets to the neighbor to verify that it is still reachable. The Hello packets also include information about the router's OSPF configuration, such as its OSPF router ID, the network type, and the OSPF interface cost.

  3. Elects designated router and backup designated router: OSPF Hello protocol uses timers to elect a designated router (DR) and a backup designated router (BDR) on multiaccess networks. The DR is responsible for forwarding LSAs to other routers on the network, while the BDR takes over if the DR fails.

  4. Detects unreachable neighbors: If a router does not receive a Hello packet from a neighbor within a certain time interval, it assumes that the neighbor is no longer reachable and removes it from its neighbor table. This detection process takes place every 30 seconds by default.

In summary, the OSPF Hello protocol performs dynamic neighbor discovery, maintains neighbor relationships, elects a designated router and backup designated router, and detects unreachable neighbors. It is an essential part of the OSPF routing protocol and helps ensure the efficient and reliable delivery of data across the network.