Chapter 5: OSPF Basics & STP Configuration

Question 1

Where is OSPF typically applied in a network (e.g., core switch, aggregated switch)?

Answer 1

OSPF is applied in both core and aggregation layers of a network for efficient and scalable routing.

Question 2

Explain the role of the Spanning Tree Protocol (STP) and how it prevents Layer 2 loops.

Answer 2

STP creates a loop-free logical topology by blocking redundant paths that could cause loops while maintaining backup paths for redundancy.

Question 3

How is the router ID determined in OSPF?

Answer 3

Router ID is determined by the highest IP address on the router’s active interfaces or manually configured.

Question 4

Identify the roles of DR and BDR in OSPF and explain how they are elected.

Answer 4

DR (Designated Router): Manages OSPF updates in a multi-access network.
BDR (Backup Designated Router): Takes over if the DR fails.
Election: Based on highest priority (configured); if equal, highest router ID.

Question 5

What is the difference between an ABR and an ASBR in OSPF, and how can you identify them?

Answer 5

ABR (Area Border Router): Connects different OSPF areas.

ASBR (Autonomous System Boundary Router): Connects OSPF to other routing domains (e.g., BGP).

Identification: ABR has interfaces in multiple areas, ASBR has external routes in the routing table.

Question 5

Describe the process of selecting a Root Bridge in STP.

Answer 5

The switch with the lowest bridge ID (priority + MAC address) is selected as the Root Bridge.