Routing Protocols Types: Static, Dynamic, IP, CISCO

By : Bryce Leo Bryce Leo
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⚡ Smart Summary

Routing protocols are the rules routers use to share reachability information and build routing tables, letting packets take the best path across networks through static routes or dynamic distance-vector, link-state, and hybrid methods such as RIP, OSPF, and BGP.

  • 🧭 Definition: Routing protocols update routing tables so routers agree on how to reach every destination.
  • 🗺️ Static vs dynamic: Static routes are set manually, while dynamic protocols adapt automatically when links change.
  • 📡 Distance vector: RIP and IGRP advertise their full routing tables to neighbors on a timer.
  • 💡 Link state: OSPF and IS-IS map the whole topology and run shortest-path calculations.
  • 🌍 Exterior routing: BGP connects autonomous systems and keeps the global Internet reachable.
  • 🤖 AI assistance: AI tools analyze routing telemetry to predict congestion and detect misconfigurations.
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Types of Routing Protocols in Networking

What is Routing Protocols?

Routing Protocols are the set of defined rules used by routers to communicate between source and destination. They do not move the data itself; they only update the routing table that holds the path information.

Routing protocols also specify how routers communicate with each other and let the network select routes between any two nodes on a computer network.

Types of Routing Protocols

There are mainly two types of network routing protocols:

  • Static
  • Dynamic

The diagram below shows how routing protocols are grouped into static and dynamic categories, along with the main dynamic protocols under each type:

Classification of static and dynamic routing protocols including RIP, IGRP, OSPF, EIGRP and BGP

Static Routing Protocols

Static routing protocols are used when an administrator manually assigns the path from the source to the destination network. This approach offers more security to the network.

Advantages

  • No overhead on the router CPU.
  • No unused bandwidth between links.
  • Only the administrator is able to add routes.

Disadvantages

  • The administrator must know how each router is connected.
  • It is not an ideal option for large networks, as it is time intensive.
  • Whenever a link fails, the network goes down, which is not feasible on large networks.

Dynamic Routing Protocols

Dynamic routing protocols are another important type of routing protocol. They help routers add information to their routing tables from connected routers automatically. These protocols also send out topology updates whenever the network’s topological structure changes.

Advantages

  • Easier to configure, even on larger networks.
  • They can dynamically choose a different route if a link goes down.
  • They help you load balance traffic between multiple links.

Disadvantages

  • Updates are shared between routers, so they consume bandwidth.
  • Routing protocols put an additional load on the router CPU and RAM.

Distance Vector Routing Protocol (DVR)

Distance Vector protocols advertise their routing table to every directly connected neighbor at specific time intervals, using a lot of bandwidth and converging slowly.

In the Distance Vector routing protocol, when a route becomes unavailable, all routing tables need to be updated with the new information.

Advantages

  • Updates of the network are exchanged periodically and are always broadcast.
  • The protocol trusts the routing information received from neighbor routers.

Disadvantages

  • Because routing information is exchanged periodically, unnecessary traffic is generated, which consumes available bandwidth.

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Internet Routing Protocols

The following are the types of protocols that help data packets find their way across the Internet. Each one falls into the distance-vector, link-state, or hybrid category described above.

Routing Information Protocol (RIP)

RIP is used in both LAN and WAN networks, and it runs on the application layer of the OSI model. Two versions of RIP exist:

  • RIPv1
  • RIPv2

The original version, RIPv1, determines network paths based on the IP destination and the hop count of the journey. RIPv1 interacts with the network by broadcasting its IP table to all routers connected to the network.

RIPv2 is a little more sophisticated, as it sends its routing table to a multicast address instead of broadcasting.

Interior Gateway Routing Protocol (IGRP)

IGRP is a distance-vector interior gateway protocol developed by CISCO. It was introduced to overcome the limitations of RIP. The metrics it uses are load, bandwidth, delay, MTU, and reliability, and it exchanges routing data within an autonomous system.

This protocol suits larger networks, as it broadcasts every 90 seconds and supports a maximum hop count of 255. It resists routing loops by updating itself automatically when routes change, and it can load balance traffic across equal or unequal metric-cost paths.

Link State Routing Protocol

Link State protocols take a unique approach to finding the best routing path. In this protocol, the route is calculated based on the speed of the path to the destination and the cost of resources.

Routing protocol tables

A link state routing protocol maintains the three tables given below:

  • Neighbor table: This table contains information about the neighbors of the router only — for example, the routers with which adjacency has been formed.
  • Topology table: This table stores information about the whole topology — for example, both the best and the backup routes to a particular advertised network.
  • Routing table: This table contains all the best routes to the advertised network.

Advantages

  • The protocol maintains separate tables for both the best route and the backup routes, so it has more knowledge of the inter-network than any distance-vector routing protocol.
  • Triggered updates are used, so it does not consume unnecessary bandwidth.
  • Partial updates are triggered only when there is a topology change, so the whole routing table does not need to be exchanged.

Exterior Gateway Protocol (EGP)

EGP is a protocol used to exchange data between gateway hosts that are neighbors within autonomous systems. It lets routers share information across different domains, including known routers, network addresses, route costs, and neighboring devices.

Enhanced Interior Gateway Routing Protocol (EIGRP)

EIGRP is a hybrid routing protocol that combines features of both distance-vector and link-state routing protocols. It routes the same protocols that IGRP routes, using the same composite metrics as IGRP, which helps the network select the best path to a destination.

Open Shortest Path First (OSPF)

Open Shortest Path First (OSPF) is a link-state IGP tailor-made for IP networks, using the Shortest Path First (SPF) method.

OSPF maintains databases detailing the surrounding topology of the network. It uses the Dijkstra shortest path algorithm to recalculate network paths when the topology changes. It is also secure, as it can authenticate protocol changes to keep data protected.

Here are some of the main differences between Distance Vector and Link State routing protocols:

Distance Vector Link State
Distance Vector protocol sends the entire routing table. Link State protocol sends only link-state information.
It is susceptible to routing loops. It is less susceptible to routing loops.
Updates are sometimes sent using broadcast. It uses only the multicast method for routing updates.
It is simple to configure. It is harder to configure.
It does not know the network topology. It knows the entire topology.
Examples: RIP, IGRP. Examples: OSPF, IS-IS.

Intermediate System-to-Intermediate System (IS-IS)

IS-IS is a CISCO routing protocol used on the Internet to send IP routing information. It consists of a range of components, including end systems, intermediate systems, areas, and domains.

Under the IS-IS protocol, routers are organized into groups called areas, and multiple areas are grouped to form a domain.

Border Gateway Protocol (BGP)

BGP is the last routing protocol on this list and the one that runs the Internet. It is classified as a distance path vector protocol (DPVP).

This protocol sends updated router table data only when changes are made. There is no auto-discovery of topology changes, which means BGP must be configured manually.

What is the purpose of Routing Protocols?

Routing protocols are required for the following reasons:

  • They allow optimal path selection.
  • They offer loop-free routing.
  • They provide fast convergence.
  • They minimize update traffic.
  • They are easy to configure.
  • They adapt to changes.
  • They scale to a large size.
  • They stay compatible with existing hosts and routers.
  • They support variable-length subnet masks.

Classful Vs. Classless Routing Protocols

Here are the main differences between these two families of routing protocols:

Classful Routing Protocols Classless Routing Protocols
Classful routing protocols never send subnet mask details during routing updates. Classless routing protocols can send IP subnet mask information during routing updates.
RIPv1 and IGRP are classful protocols, as they do not include subnet mask information. RIPv2, OSPF, EIGRP, and IS-IS are classless protocols, as they carry subnet mask information within their updates.

RIP, IGRP, OSPF and EIGRP Compared

The table below summarizes how the most common routing protocols differ:

Features RIP v1 RIP v2 IGRP OSPF EIGRP
Classful/Classless Classful Classless Classful Classless Classless
Metric Hop Hop Composite Bandwidth (Cost) Composite (Bandwidth, Delay)
Periodic update 30 seconds 30 seconds 90 seconds None None (triggered)
Advertising address 255.255.255.255 224.0.0.9 255.255.255.255 224.0.0.5 / 224.0.0.6 224.0.0.10
Category Distance Vector Distance Vector Distance Vector Link State Hybrid
Default administrative distance 120 120 100 110 90

FAQs

A routed protocol, such as IP, carries user data. A routing protocol, such as OSPF or RIP, carries none — it exchanges reachability information so routers build the tables that forward the routed protocol.

Different protocols use different metrics. RIP uses hop count, OSPF uses cost from bandwidth, and IGRP and EIGRP use a composite of bandwidth, delay, load, and reliability. The lowest-metric route is preferred.

Administrative distance ranks how trustworthy a routing source is when several protocols offer a route to the same network. The lower value wins: EIGRP is 90, OSPF is 110, and RIP is 120.

Convergence is the time it takes for every router to agree on the network topology after a change, such as a failed link. Link-state protocols like OSPF converge faster than distance-vector protocols like RIP.

An autonomous system (AS) is a group of networks under one administrative control with a common routing policy. Interior protocols like OSPF run inside an AS, while BGP routes traffic between different autonomous systems.

Modern routing protocols support authentication, so routers only accept updates from trusted neighbors. OSPF, EIGRP, and BGP can use MD5 or SHA keys to block spoofed route advertisements that could hijack or blackhole traffic.

AI and machine learning analyze routing telemetry to predict congestion, detect misconfigurations, and suggest optimal paths in software-defined networks. They can reroute traffic proactively, though engineers still review major changes before production.

GitHub Copilot can draft router configuration snippets and automation scripts for OSPF, EIGRP, or BGP. Always test the generated commands in a lab first, since a wrong network statement can black-hole live traffic.

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