2.1 - Characteristics of Routing Technologies

Routing

The process of selecting paths in a network along which to send network traffic. Routing is performed by devices known as routers, which use routing tables and algorithms to determine the most efficient path for data packets to travel from their source to their destination.

Static Routing

Involves manually configuring routers with specific paths to reach network destinations. It is simple to implement in small networks but lacks the flexibility and scalability of dynamic routing, as it does not automatically adjust to network changes.

Dynamic Routing

Automatically adjusts the paths used to send data through the network. Routers communicate with each other using dynamic routing protocols, sharing information about network topology and traffic conditions. This allows the network to adapt to changes, such as link failures or congestion, ensuring data takes the most efficient route.

Border Gateway Protocol

BGP is the protocol underlying the global routing system of the internet. It is used for routing data between autonomous systems (ASes), which are networks managed by single organizations. BGP is crucial for ensuring that data can be routed across the internet, regardless of the path it needs to take between source and destination.

Enhanced Interior Gateway Routing Protocol

EIGRP is a Cisco proprietary advanced distance-vector routing protocol that combines features of both distance-vector and link-state protocols. It provides rapid convergence and efficiency with less bandwidth usage and supports multiple network layer protocols.

Open Shortest Path First

OSPF is a link-state routing protocol that provides fast, efficient path selection using the shortest path first (SPF) algorithm. It scales well to larger network architectures and supports complex topologies by dividing them into areas to optimize routing.

Route Selection

A critical process in network routing that determines the best path for data to travel from source to destination. It uses specific criteria such as administrative distance, prefix length, and metric to choose the most efficient route.

Administrative Distance

A metric used by routers to rank the trustworthiness of routes received from different routing protocols. Lower values indicate more preferred routes, helping routers decide which routes to use when multiple paths to the same destination exist from different sources.

Prefix Length

Specifies the number of contiguous bits of the network mask that are set to 1. It effectively divides the IP address into the network portion and the host portion. In IP addressing, prefix length is denoted by a slash followed by the number, such as /24 in IPv4 or /64 in IPv6, indicating that 24 and 64 bits, respectively, are used for the network portion. This notation is an integral part of CIDR and helps in defining network boundaries and available hosts within those networks, enhancing both routing efficiency and address allocation.

Metric

A value associated with routes, used by routing protocols to evaluate the cost of path traversal. Lower metric values typically indicate more desirable routes. Different routing protocols may use various factors, such as bandwidth, delay, hop count, or even custom values, to calculate this metric.

Network Address Translation

A method used to modify network address information in IP packet headers while in transit across a traffic routing device, typically for the purpose of remapping one IP address space into another. NAT allows multiple devices on a private network to access the internet using a single public IP address, enhancing security by hiding internal IP addresses from the external network. This process is essential for conserving the limited number of available public IP addresses and for allowing private network communication externally.

Port Address Translation

Often referred to as "NAT overload", this is a type of NAT that allows multiple devices on a local network to be mapped to a single public IP address but with a different port number for each session. PAT enables multiple connections from different devices to be distinguished from one another using a single public IP address, significantly increasing the scalability of NAT by allowing thousands of simultaneous connections through a few public IPs. This technique is widely used in small office and home office (SOHO) networks to allow multiple devices to share a single or a few public IP addresses for Internet connectivity.

Virtual Router Redundancy Protocol/First Hop Redundancy Protocol

VRRP allows for automatic assignment of available routers to participating hosts, ensuring continuous network availability even if one router fails. FHRP is a general term for protocols like VRRP that provide the ability to automatically failover to a backup router in case of the primary router failure, minimizing downtime and maintaining network resilience.

Virtual IP

An IP address that is not tied to a specific physical network interface on a device. It is used to provide redundancy and load balancing for services hosted on multiple servers, allowing several servers to share the same IP address. VIPs are commonly used in network load balancers and failover configurations to ensure continuous availability and scalability of critical applications and services.

Subinterface

A virtual interface created by dividing a single physical interface into multiple logical interfaces. This is commonly used in scenarios where multiple VLANs exist on a single router or switch interface to manage traffic segregation and support various services or protocols over a single physical link. Subinterfaces are treated like separate interfaces, allowing for individual configuration settings such as IP addresses, access control policies, and routing configurations. This method enhances network flexibility and efficiency, enabling more detailed traffic management and security enforcement without requiring additional hardware.