Static and Dynamic Routing in Computer Networks
1. Static Routing:
Static routing involves manually configuring the routing table entries on each router or network device. The network administrator manually defines the paths that packets should take to reach specific destination networks.
Characteristics of static routing:
- Routing table entries are manually configured and do not change unless the administrator modifies them.
- Suitable for small, stable networks where topology changes are infrequent.
- Offers better security as the routing information is not shared with other routers.
- Requires manual intervention for any network changes or updates, which can be time-consuming and prone to errors in large networks.
- No overhead for routing protocol communication.
2. Dynamic Routing:
Dynamic routing uses routing protocols to automatically learn and maintain routing information. Routers exchange routing updates with each other and dynamically update their routing tables based on the received information.
Characteristics of dynamic routing:
- Routing protocols (e.g., OSPF, EIGRP, BGP) are used to discover network topology and share routing information.
- Routing tables are automatically updated when network changes occur, such as link failures or new networks being added.
- Suitable for large, complex networks with frequent topology changes.
- Provides fault tolerance and redundancy by automatically rerouting traffic if a link goes down.
- Routing protocols introduce overhead due to the exchange of routing updates between routers.
- Configuration is more complex compared to static routing, but easier to manage in large networks.
Dynamic routing protocols can be further classified into two main categories:
a. Interior Gateway Protocols (IGPs):
IGPs are used for routing within a single autonomous system (AS), such as an organization's internal network. Examples include OSPF (Open Shortest Path First) and EIGRP (Enhanced Interior Gateway Routing Protocol).
b. Exterior Gateway Protocols (EGPs):
EGPs are used for routing between different autonomous systems, typically across Internet Service Providers (ISPs) or large organizations. The primary EGP is BGP (Border Gateway Protocol).
The choice between static and dynamic routing depends on factors such as network size, complexity, requirements for fault tolerance, and administrative preferences. Static routing is often used in small, stable networks, while dynamic routing is preferred for larger, more complex networks with frequent changes. In many cases, a combination of static and dynamic routing is employed, where static routes are used for specific paths, and dynamic routing protocols handle the rest of the network.