Dynamic Routing - CompTIA Network+ N10-009 - 2.1

Summary

The video script discusses the shift from static to dynamic routing in network administration. It explains how static routing requires manual configuration on every router, which can be inefficient in large networks. Dynamic routing automates this process, allowing routers to discover and update routes autonomously, reducing the need for manual intervention. The script covers the overhead involved in dynamic routing, such as CPU and memory usage, and the initial configuration of routing protocols. It also explores the process of routers communicating and updating routing tables in real-time, and the importance of choosing the right dynamic routing protocol based on network needs. Protocols like EIGRP, OSPF, and BGP are mentioned, each with its own advantages and use cases, such as EIGRP's quick convergence and OSPF's compatibility across manufacturers. The script concludes by emphasizing the importance of dynamic routing in managing large and complex networks efficiently.

Takeaways

• ⚙️ Static routing requires manual configuration of routes on every router, which can be impractical for large networks.
• 🤖 Dynamic routing automates the process of discovering and updating routes among routers.
• 🔄 Dynamic routing protocols allow routers to automatically update each other about the best routes.
• 🚀 With dynamic routing, network administrators don't need to manually configure or update routes when network infrastructure changes.
• 💻 Routers require additional CPU and memory to handle the overhead of dynamic routing.
• 🛠️ Initial configuration of a dynamic routing protocol is necessary, which may vary in complexity.
• 🌐 Dynamic routing protocols like EIGRP, OSPF, and BGP make different routing decisions based on various criteria.
• 🔄 EIGRP is known for quick convergence and is easy to set up, but is often used in Cisco-centric environments.
• 🌐 OSPF is a link-state protocol used across different manufacturers' devices and can assign costs to links for routing decisions.
• 🌐 BGP is used for routing outside of an autonomous system, like connecting to the internet.
• 🔄 Dynamic routing protocols help routers adapt quickly to network changes, such as adding or removing routers.

Q & A

What is static routing?

Static routing is a method where the network administrator manually configures every route on every router in the organization.

Why might static routing be impractical in large networks?

In large networks with tens or hundreds of routers, static routing becomes impractical due to the significant administrative overhead and the need for constant manual updates.

What is dynamic routing and how does it differ from static routing?

Dynamic routing is a process where routers automatically discover and update routes among themselves, eliminating the need for manual static route configurations by the network administrator.

How do routers update each other about the best routes in dynamic routing?

Routers in dynamic routing update each other by sending routing updates and receiving them, which helps them to discover new routes and update their routing tables accordingly.

What is the overhead required for dynamic routing?

Dynamic routing requires additional CPU and memory usage within the router to automatically discover routes and update routing tables.

What is the initial configuration required for setting up dynamic routing?

The initial configuration for dynamic routing involves setting up the dynamic routing protocol, which may require varying levels of planning and engineering.

How does dynamic routing handle the addition or removal of routers in a network?

Dynamic routing automatically updates the routing tables across the network when a new router is added or an existing one is removed, without requiring user intervention.

What is EIGRP and how does it function in dynamic routing?

EIGRP (Enhanced Interior Gateway Routing Protocol) is a dynamic routing protocol that efficiently updates routing tables by sending updates over minimal network traffic and quickly converging on routing changes.

What are some advantages of using EIGRP in a Cisco-centric environment?

EIGRP is advantageous in a Cisco-centric environment because it is relatively easy to set up, converges quickly, and is good at identifying loops and preventing them.

What is OSPF and how does it determine the best route?

OSPF (Open Shortest Path First) is a dynamic routing protocol that uses a link-state approach to determine the best route based on the least cost, which is often associated with throughput, link availability, and traversal time.

Why might BGP be used in a network?

BGP (Border Gateway Protocol) is used for routing traffic outside of an autonomous system, such as to other organizations or the internet, and is designed to handle dynamic updates across large networks like the internet.

Outlines

00:00

⚙️ Introduction to Static and Dynamic Routing

Static routing involves manual configuration of routes on each router, which can become a complex task as the number of routers increases. Dynamic routing automates this process, allowing routers to discover and update routes automatically. This eliminates the need for network administrators to manually update routing tables when changes occur. However, dynamic routing requires more resources, like CPU and memory, and involves configuring dynamic routing protocols. The routers will automatically update and adapt to network changes such as adding or removing routers.

05:02

🌐 Dynamic Routing Example with EIGRP

In a network scenario with multiple routers, such as Router 1, which is directly connected to certain subnets but unable to see others, dynamic routing can automatically update its routing tables. The EIGRP protocol enables Router 1 to receive updates from Router 2 and Router 3 about new routes, allowing Router 1 to update its routing table without manual intervention. These updates happen in real time, providing automatic adjustment to the network topology. This ensures that routing tables are kept current as routers are added or removed from the network.

🚦 The Mechanism Behind Dynamic Routing

Dynamic routing involves several processes: routers listen for routing updates from others and adjust their routing tables based on these updates. These updates are often sent via multicast directly between routers. Once a router receives an update, it compares the new information with its existing routes to determine the best path. Different routing protocols use various criteria to make these decisions, and changes in the network infrastructure trigger routers to notify others. This ensures that all routers maintain an accurate and efficient routing table as the network evolves.

🔍 Choosing the Right Dynamic Routing Protocol

The choice of a dynamic routing protocol depends on various factors, such as whether routing decisions should be based on link state or hop count, and how quickly updates should be made. Routing protocols vary in how they assess the best path and how fast they react to network changes. Protocols like BGP and OSPF are widely supported across multiple vendors, while EIGRP is primarily Cisco-specific. Despite this, EIGRP can be easy to set up in Cisco environments and is highly efficient in preventing loops and conserving bandwidth.

🔄 Understanding EIGRP and Its Benefits

EIGRP, a Cisco-centric routing protocol, offers quick convergence and efficient routing table updates. It is designed to minimize network traffic while maintaining updated routes between routers. EIGRP detects other EIGRP-enabled routers and sends updates only when necessary. This efficiency helps preserve network bandwidth for other applications. Although proprietary to Cisco, EIGRP can be found on some non-Cisco routers and is relatively simple to configure, making it an attractive choice for organizations with a Cisco-heavy infrastructure.

🌍 OSPF: A Standardized Dynamic Routing Protocol

OSPF (Open Shortest Path First) is a widely supported dynamic routing protocol used across various manufacturers' devices. It is commonly implemented in autonomous systems (AS), such as large-scale networks with multiple routers. As a link-state protocol, OSPF calculates the best route based on factors like link cost, availability, and throughput. OSPF allows for efficient routing decisions by assigning lower costs to better-performing links. It also supports load balancing across identical-cost paths and is ideal for controlled networks with multiple routers.

🌐 BGP: Routing Across Autonomous Systems and the Internet

BGP (Border Gateway Protocol) is the go-to protocol for routing between autonomous systems, especially in large-scale networks like the internet. Known for its role in connecting different organizations and internet service providers, BGP handles the complexity of updating routes across the global internet. BGP is often used by organizations with multiple internet connections and can dynamically route traffic to and from external networks. It's regarded as a robust solution for managing large-scale, distributed networks.

Keywords

💡Static Routing

Static routing refers to the manual configuration of network routes by a network administrator on each router. This method can be manageable for small networks with few routers, but it becomes inefficient and time-consuming as the network grows. In the video, it is contrasted with dynamic routing, which automates the process and is more suitable for larger networks.

💡Dynamic Routing

Dynamic routing is a method of automatically configuring routing tables in a network. Routers discover and update routes among themselves without manual intervention from a network administrator. This concept is central to the video's theme, as it presents a more efficient alternative to static routing, especially for large and complex networks.

💡Routing Protocol

A routing protocol is a set of rules that govern how routers exchange information about routes and how to select the best path for network traffic. The video discusses various routing protocols like EIGRP, OSPF, and BGP, each with its own method for determining the best route and updating routing tables.

💡EIGRP (Enhanced Interior Gateway Routing Protocol)

EIGRP is a dynamic routing protocol developed by Cisco that is known for its efficiency and quick convergence. It is highlighted in the video as being easy to set up and effective at preventing routing loops. EIGRP is particularly suitable for networks with a high percentage of Cisco routers.

💡OSPF (Open Shortest Path First)

OSPF is a link-state routing protocol that is vendor-neutral and can be used across different manufacturers' devices. It calculates the best path based on the least cost, which considers factors like link speed and availability. The video mentions OSPF as a common choice for networks where the organization has control over all devices.

💡BGP (Border Gateway Protocol)

BGP is a routing protocol designed for routing between different autonomous systems, such as connecting to the internet. It is discussed in the video as a protocol that can handle the complex task of routing across the internet and is essential for organizations that need to dynamically route traffic to external networks.

💡Routing Table

A routing table is a database that contains a list of routes and their destinations, along with instructions on how to forward network traffic. In the context of the video, dynamic routing protocols automatically update these tables, ensuring that network traffic is directed efficiently through the best available routes.

💡Convergence

Convergence in routing refers to the process of routers in a network reaching an agreement about the best paths to various network destinations. The video emphasizes the speed of convergence as an important aspect of routing protocols, with EIGRP being noted for its quick convergence after network changes.

💡Routing Loop

A routing loop occurs when network traffic is forwarded in a continuous cycle between routers, causing packets to be lost or delayed. The video mentions that EIGRP is capable of identifying and preventing routing loops, which is crucial for maintaining network stability and efficiency.

💡Autonomous System (AS)

An autonomous system is a collection of routers under a single administrative domain that presents a unified routing policy to the internet. The video discusses OSPF in the context of an AS, where it is used to manage routing within a network that the organization fully controls.

💡Link-State Protocol

A link-state protocol is a type of routing protocol that builds a map of the network by exchanging information about the state of each link with all other routers. OSPF is an example of a link-state protocol mentioned in the video, which uses this information to calculate the best path for routing traffic.

Highlights

Static routing requires manual configuration of every route on every router.

Dynamic routing automates the process of discovering and updating routes among routers.

Dynamic routing reduces the administrative burden of managing large networks.

Routers automatically update each other about the best routes in dynamic routing.

Dynamic routing protocols require CPU and memory resources for route discovery.

Initial configuration of dynamic routing protocols is necessary.

Network changes, such as adding or removing routers, are automatically recognized in dynamic routing.

Routers update their routing tables in real-time without user intervention.

EIGRP is a dynamic routing protocol that sends routing updates to other routers.

EIGRP is known for quick convergence and loop prevention.

OSPF is a dynamic routing protocol that works across different manufacturers' devices.

OSPF is a link-state protocol that assigns costs to links for routing decisions.

OSPF allows for load balancing across links with identical costs.

BGP is used for routing traffic outside of an autonomous system, such as the internet.

BGP dynamically updates routes across the entire internet.

Different routing protocols make decisions based on various criteria like link state or hop count.

The choice of routing protocol depends on network requirements and existing infrastructure.

Transcripts

Static routing requires the network administrator manually

configure every route on every router in the organization.

If you have three or four routers,

that might not be a big problem.

But if you have tens or even hundreds of routers,

you might want to have a more automated way for configuring

your routing tables.

One way to do that is through the process of dynamic routing.

Dynamic routing will have the routers

handle this process for you, automatically discover

these routes, and update each other as to where

the best route might be.

This means that you as the network administrator

don't have to do any type of static route configuration.

You don't have to SSH into the router,

make any configuration changes, or update

those routes if anything changes with your network

infrastructure.

Any time you bring a new router online, all of the other routers

will automatically know where the new route is.

And if you happen to remove a router from the network,

all of the routers also know that that route is now

no longer available.

There is a bit of overhead required inside of the router

to be able to automatically discover these routes

and update the routing tables.

This will require some CPU and memory inside of the router,

so you may need to do additional monitoring

to make sure that your router is able to handle that load.

This also requires you to initially configure

the dynamic routing protocol.

This may be a relatively easy configuration process,

or it may require additional planning and engineering

to be able to implement it properly

in the config of the router.

Let's look at this network configuration where we have Sam

that may want to communicate across the network to Jack

or to Teal'c.

You'll notice that there are three different routers.

And for this particular example, let's focus on router one.

You'll notice that router one is directly connected

to three different subnets, but there

are two subnets on the other side of router two

and router three that router one simply can't see.

So we need some way to update router one

with those additional routes.

One way to do this would be to have router

to send a routing update via EIGRP to router one.

Router one receives that update and then updates its own routing

table with this new route to 10.10.20.0/24.

And the way that you get to that network is to go to 10.10.40.2.

We also have another EIGRP update that

has come from router three.

And when that update is received,

router one identifies a new route to 10.10.30.0.

That's the subnet down at the bottom.

And you can see that the next hop is 10.10.50.2.

All of these updates occurred in real time behind the scenes

without any type of user intervention.

And if we happen to add or remove routers

from this network, this routing table

will be updated with an additional EIGRP

update that will either add or remove

those routes from the table.

Although it looks relatively straightforward to perform

these dynamic routing updates, there's actually a lot of work

that occurs behind the scenes.

First, the router needs to listen to the traffic that

is on the local subnet and see if there are other routers that

are sending routing updates that it can use

to build its own routing table.

These are very often sent directly from router to router,

either directly or with a multicast.

Once a router then builds its routing table,

it needs to inform other routers of routes that it knows.

So it will send its own multicast

to other routers that are nearby,

informing them of all of the routes

that that router happens to know.

Once the other routers receive this update,

they need to interpret this information

and determine if that's a better route than what they already

have or if they should use this as a secondary route.

Different routing tables use different methods

to make these decisions, and they

will update their routing tables differently

depending on the protocol you happen to be using.

And of course, if there is any change to the network

infrastructure, these routers need

to inform all of the other routers

that the change has occurred.

So if we add a new link into our router, we remove a router,

or we add a router, we need to make sure

that all of our routing tables are updated

across the entire network.

There are a number of different dynamic routing protocols

to choose from.

So which one would be the best for

your particular implementation?

Different routing protocols make routing decisions

in different ways.

For example, would you like your traffic to be routed based

on the state of the link-- whether the link is up or down--

or would you like to be able to make that decision based

on the number of hops that a link might be away

from you or the speed of that connection?

Based on the routing protocol that you're using,

that decision might be very different.

Some routing protocols will use a different criteria

to determine the best way to get to a remote location.

You might also find that some routing protocols are

able to make changes very quickly if anything happens

to the underlying infrastructure.

So if you add a new router to the network,

it might take a number of seconds

or it might take a minute, depending

on the type of dynamic routing protocol that you're using.

And in some cases, we need to take into account the type

of router that we're using.

Some routing protocols such as BGP and OSPF are very common

and can be used across many manufacturers' devices.

Some routing protocols such as EIGRP

may work best in a Cisco-centric environment.

So if you have a lot of Cisco routers,

that might be a better routing protocol for you.

Although EIGRP tends to be very Cisco-centric,

you may find EIGRP is also available on

other manufacturers' routers.

But there are some aspects of EIGRP

that are proprietary to Cisco, so you

tend to see it mostly in Cisco-related configurations.

But one advantage of EIGRP is that it

is relatively easy to set up.

You would turn on EIGRP in your Cisco router,

give it a few minor configuration options,

and it's now up and running with the EIGRP protocol.

When there are changes, EIGRP tends

to converge relatively quickly, and it's also

able to identify any loops and prevent those from occurring

on your routed network.

EIGRP is also very good at identifying other EIGRP enabled

routers and sending updates over a minimum of network traffic.

This keeps your network more efficient

and leaves your bandwidth available

for other applications.

If you want a more generic dynamic routing protocol that

can be used across different manufacturers' routers,

then you might want to try OSPF.

This is the Open Shortest Path First routing protocol,

and it's one that you'll find available

on a number of different manufacturers' devices.

This is often implemented in a network

where you have complete control of those systems.

We often refer to this as an AS, or an Autonomous System.

For example, if you're running a wide area network that

has 50 different routers, those 50 routers

would be part of your single autonomous system.

Another advantage of OSPF is that it's

available on many different manufacturers' devices.

This is a common standard, and you

can download this standard from the internet

and read through every aspect of OSPF.

We refer to OSPF as a link-state protocol, which

means it determines what the best route is based

on uptime and availability between the different OSPF

routers.

OSPFs can be used to assign costs to an individual link,

so certain links may have a higher cost than another.

This allows OSPF to make routing decisions

based on what the least cost might be.

This cost is often associated with how much throughput

may be available on a particular link,

if that link is up or down, and how long it takes to traverse

that particular connection.

With OSPF, the lowest cost and the fastest path

is going to be the best route to a remote location.

And if there are identical costs on OSPF,

many implementations will allow you to load balance

across both of those links.

If you need to route traffic outside of your autonomous

system to other organizations, then you

might want to use an external gateway protocol such as BGP.

BGP is the Border Gateway Protocol,

and it's commonly used on our wide area networks and internet

connections.

Connecting the internet together and being

able to dynamically update the routes on the entire internet

is a daunting task, and this particular routing protocol

was designed with this specific task in mind.

Sometimes you'll hear BGP referred

to as the three-napkins protocol because it was sketched out

on napkins initially to solve this particular type of problem.

If your organization has one or more connections to the internet

and you want to be able to dynamically route

to those internet sites, then you'll

want to use a protocol such as BGP.