Overview
This lecture explains how routers use routing protocols to share information and update routing tables, focusing on interior gateway protocols, specifically distance vector and link state protocols.
Routing Protocol Basics
- Routing tables are continuously updated with new information for optimal network paths.
- Routers use routing protocols to share network path information with each other.
- Routing protocols enable routers across the globe to learn about distant networks.
Types of Routing Protocols
- Routing protocols are divided into interior gateway protocols (IGPs) and exterior gateway protocols (EGPs).
- IGPs operate within a single autonomous system (AS), which is a set of networks managed by one organization.
- EGPs handle information exchange between independent autonomous systems.
- IGPs are further split into distance vector and link state protocols.
Distance Vector Protocols
- Distance vector protocols send routing table lists (vectors) with hop distances to directly connected neighboring routers.
- Routers using distance vector protocols know only about their neighbors, not the wider network.
- Example: Router A can update its routing table if Router B shows a shorter path to a network.
- Main limitation: Routers may react slowly to faraway network changes.
Link State Protocols
- Link state protocols advertise the status of each router's interfaces (links) to all routers in the AS.
- Every router gains a full view of the entire AS and can compute the best paths using complex algorithms.
- Link state protocols require more memory and processing power.
- Advances in hardware have made link state protocols more popular than distance vector protocols.
Key Terms & Definitions
- Routing Protocol — A protocol routers use to share and update path information across networks.
- Routing Table — A list of known networks and the best paths to reach them.
- Autonomous System (AS) — A collection of networks managed by a single organization.
- Interior Gateway Protocol (IGP) — A routing protocol used within a single AS.
- Exterior Gateway Protocol (EGP) — A routing protocol used between different ASes.
- Distance Vector Protocol — An IGP where routers share lists of network distances with neighbors.
- Link State Protocol — An IGP where routers share interface status to all within the AS.
Action Items / Next Steps
- Review examples of routing protocol updates in practice.
- Prepare for further study of exterior gateway protocols in upcoming lessons.