What are the major routing protocols used in networking and how do they work?

There are several major routing protocols used in networking, including Routing Information Protocol (RIP), Open Shortest Path First (OSPF), Border Gateway Protocol (BGP), and Enhanced Interior Gateway Routing Protocol (EIGRP). Each of these protocols operates differently and is used in different network environments.

1. Routing Information Protocol (RIP):
RIP is a distance-vector routing protocol that uses hop count as the metric to determine the best path to a destination network. It exchanges routing information with neighboring routers and updates its routing table accordingly. RIP has a maximum hop count of 15, which limits its scalability in larger networks.

2. Open Shortest Path First (OSPF):
OSPF is a link-state routing protocol that uses the Shortest Path First (SPF) algorithm to determine the best path to a destination network. It exchanges link-state advertisements (LSAs) with neighboring routers to build a complete topology map of the network. OSPF supports variable-length subnet masking (VLSM) and provides faster convergence compared to RIP.

3. Border Gateway Protocol (BGP):
BGP is an exterior gateway protocol used for routing between autonomous systems (AS) in the Internet. It operates based on path-vector routing, where it exchanges routing information and attributes with neighboring routers to determine the best path to a destination network. BGP is highly scalable and provides policy-based routing capabilities.

4. Enhanced Interior Gateway Routing Protocol (EIGRP):
EIGRP is a Cisco proprietary routing protocol that combines features of both distance-vector and link-state protocols. It uses the Diffusing Update Algorithm (DUAL) to calculate the best path to a destination network. EIGRP exchanges routing information and metric values with neighboring routers and supports load balancing and route summarization.

These routing protocols work by exchanging routing information with neighboring routers, either through periodic updates or triggered updates when there are changes in the network topology. They use various metrics, such as hop count, bandwidth, delay, and reliability, to determine the best path to a destination network. The routers build and maintain their routing tables based on the received routing information, allowing them to forward packets to their intended destinations efficiently.

Overall, the choice of routing protocol depends on the network size, complexity, and requirements. Each protocol has its advantages and disadvantages, and network administrators need to consider these factors when selecting the appropriate routing protocol for their network.