Free CCNA | Dynamic Routing | Day 24 | CCNA 200-301 Complete Course

Name: Free CCNA | Dynamic Routing | Day 24 | CCNA 200-301 Complete Course
Uploaded: 2020-07-19T11:00:24.000Z
Duration: 1 h 28 min 38 s

Welcome to Jeremy’s IT Lab

In this section, Jeremy introduces his free CCNA course and discusses the focus on dynamic routing protocols.

Introduction to Dynamic Routing Protocols

Dynamic routing involves configuring a routing protocol on the router to automatically find the best routes to destination networks.

Dynamic routing protocols allow routers to inform each other about new destination networks and adapt when paths become unavailable.

The CCNA exam heavily covers IP Connectivity (3.0), which includes dynamic routing protocols.

Overview of Dynamic Routing Protocols

Jeremy plans to review missed topics from IP Connectivity and provide an overview of dynamic routing protocols in this video.

He will cover RIP and EIGRP in Day 25, followed by OSPF in the next few days. Understanding other dynamic routing protocols is important for comparing them with OSPF.

How Dynamic Routing Protocols Work

Jeremy explains how dynamic routing protocols function and why they are preferred over static routes.

Different types of dynamic routing protocols exist, which will be discussed further. Metrics are used to determine the best route, along with administrative distance.

Network Topology and Route Tables

This section focuses on network topology, route tables, and the difference between network routes and host routes.

Network Topology Demonstration

Jeremy presents a network topology with four routers: R1, R2, R3, and R4 connected to a LAN (192.168.4.0/24). The demonstration will primarily focus on R1's perspective for now.

Without any static or dynamic routes configured, R1's routing table only contains connected and local routes.

Network Routes vs Host Routes

Jeremy clarifies the difference between network routes (routes to a network or subnet) and host routes (routes to a specific host).

Static routes can be configured for both network and host routes using the IP ROUTE command.

Dynamic Routing with Route Advertisements

Instead of manually configuring static routes, enabling a dynamic routing protocol allows routers to advertise networks to each other.

R4 advertises the 192.168.4.0/24 network to R2, which then advertises it to R1. R1 adds this route to its route table automatically.

Adaptation and Backup Routes

If a link failure occurs, dynamic routing protocols automatically adapt by removing invalid routes from route tables.

Adding backup connections ensures that instead of completely removing a destination network, it is replaced with the next-best route in the route table.

Conclusion

This section concludes the video by emphasizing the benefits of dynamic routing over static routing.

Benefits of Dynamic Routing

Dynamic routing removes invalid routes automatically, preventing traffic from being sent to dead-end destinations.

Having backup routes ensures continuous connectivity even in case of link failures.

New Section

In this section, the speaker explains why the route via R2 was preferred over the route via R3 in a network. The concept of "root cost" and its role in determining the best path to the root bridge is introduced. Dynamic routing protocols are also discussed.

Why was the route via R2 preferred?

The connection via R2 was preferred because it is a fastethernet connection, while the connection via R3 is a gigabit ethernet.

The concept of "root cost" is used to determine the best path to the root bridge.

Dynamic routing protocols use a similar concept to determine the best path to a destination.

How do dynamic routing protocols work?

Routers can use dynamic routing protocols to advertise information about their connected routes and routes learned from other devices.

They form adjacencies or neighbor relationships with adjacent routers to exchange this information.

If multiple routes to a destination are learned, the router determines which route is superior based on its metric and adds it to the routing table.

New Section

This section provides an overview of different types of dynamic routing protocols - Interior Gateway Protocols (IGPs) and Exterior Gateway Protocols (EGPs). It explains how IGPs are used within a single autonomous system (AS), while EGPs are used between different ASs.

What are IGPs and EGPs?

IGPs are used to share routes within a single autonomous system (AS), such as within a company.

EGPs are used to share routes between different autonomous systems, such as between companies or ISPs.

New Section

This section further breaks down IGPs and EGPs by discussing algorithm types. It mentions that BGP is the only EGP used in modern networks and focuses on IGPs, particularly OSPF.

Algorithm types in routing protocols

EGPs use a single algorithm type called Path Vector, with BGP being the only EGP used in modern networks.

IGPs can be further divided into two algorithm types: distance vector and link state.

OSPF is an IGP that uses the link state algorithm.

New Section

This section provides an overview of distance vector and link state protocols. It mentions RIP and EIGRP as examples of distance vector protocols, while OSPF and IS-IS are mentioned as link state protocols.

Distance vector protocols

Distance vector protocols, such as RIP and EIGRP, were invented before link state protocols.

These protocols operate by sharing information about known destination networks and their metrics to reach those destinations.

The router only knows about the routes its neighbors tell it, hence the term "routing by rumor."

New Section

This section emphasizes the importance of understanding different routing protocol names and their associated algorithms. It highlights that RIP and EIGRP use a distance vector algorithm, OSPF and IS-IS use a link state algorithm, while BGP uses a path vector algorithm.

Characteristics of distance vector and link state protocols

Distance vector protocols like RIP and EIGRP rely on routers sharing information about known destination networks and their metrics.

Link state protocols like OSPF develop a more complete picture of the network by exchanging detailed information about network topology.

Understanding the names of routing protocols along with their associated algorithms is crucial for exam preparation.

The summary provided above covers multiple sections from the transcript. Each section has been summarized concisely using bullet points.

Link State Routing Protocols

In this section, the instructor introduces link state routing protocols and explains how they differ from distance vector routing protocols. The two link state protocols discussed are OSPF and IS-IS.

Introduction to Link State Routing Protocols

Link state routing protocols create a "connectivity map" of the network where each router has the same map.

Each router advertises information about its interfaces and connected networks to its neighbors.

Advertisements are passed along to other routers until all routers have the same map of the network.

Each router independently uses this map to calculate the best routes to each destination.

Advantages of Link State Routing Protocols

Link state protocols provide a complete picture of the network, allowing for more accurate route calculations.

These protocols react faster to changes in the network compared to distance vector protocols.

However, they require more resources such as CPU power and memory due to sharing more information.

Examples of Link State Routing Protocols

OSPF (Open Shortest Path First) is one of the most widely used link state routing protocols.

IS-IS (Intermediate System-to-Intermediate System) is another link state protocol commonly used in large service provider networks.

Routing Metrics

This section discusses metrics used by routing protocols to determine the best routes. The instructor explains that different routing protocols use different metrics and provides an example using RIP and EIGRP.

Determining Best Routes

A router's route table contains the best route to each destination network it knows about.

If a router learns multiple routes with different metrics, it needs a way to determine which is best.

The metric value of a route is used for this purpose, with lower values considered better.

Metric Usage in Different Routing Protocols

Each routing protocol uses a different metric to determine the best route.

RIP (Routing Information Protocol) uses a simple hop count as its metric, where each router in the path counts as one hop.

EIGRP (Enhanced Interior Gateway Routing Protocol) uses a more complex metric based on bandwidth and delay.

Example of Metric Usage

In an example with two paths to the same destination network, only the route with the lowest metric is added to the routing table.

The interface with the lowest root cost becomes the root port in spanning tree protocol.

Equal Cost Multipath Load-Balancing

This section explains how equal cost multipath load-balancing works and provides an example using OSPF.

Equal Cost Multipath Load-Balancing

When a router learns multiple routes via the same routing protocol to the same destination with equal metrics, both routes are added to the routing table.

Traffic will be load-balanced over both routes, provided they have exactly the same destination network address and prefix length.

Example of Equal Cost Multipath Load-Balancing

In an example using OSPF, two routes with equal metrics are learned for 192.168.4.0/24 via different routers.

Both routes are added to the routing table, and traffic will be load-balanced over them.

Routing Metrics: Summary

This section summarizes different metrics used by routing protocols and provides an overview of RIP's hop count metric and EIGRP's bandwidth and delay-based metric.

Summary of Routing Metrics

Different routing protocols use different metrics to determine best routes.

RIP uses a simple hop count metric where each router in the path counts as one hop.

EIGRP uses a more complex metric based on bandwidth and delay, considering only the slowest link's bandwidth and total delay values of all links in the path.

New Section

This section discusses the metrics used by different routing protocols to select the best route to a destination. It explains how RIP, EIGRP, OSPF, and IS-IS use different metrics such as hop count, bandwidth and delay calculations, and cost based on bandwidth. The purpose of these metrics is to help routers choose the most optimal route.

Metrics Used by Routing Protocols

RIP: Uses hop count as its metric for selecting routes.

EIGRP: Calculates metric based on bandwidth and delay.

OSPF: Determines cost based on bandwidth.

IS-IS: Uses a default cost of 10 for all links.

Impact of Metrics on Route Selection

RIP vs OSPF: RIP considers both routes with equal hop counts, even if one has slower connection speed. In contrast, OSPF takes into account bandwidth and selects the faster route.

Administrative Distance (AD): AD is used when comparing routes learned from different routing protocols. Lower AD indicates higher preference for a routing protocol.

Administrative Distances of Common Routing Protocols

Directly connected networks: AD 0

Static routes: AD 1

External BGP (eBGP) routes: AD 20

EIGRP internal routes: AD 90

IGRP (older version of EIGRP) routes: AD 100

OSPF routes: AD 110

IS-IS routes: AD 115

RIP routes: AD 120

These values are specific to Cisco devices and may vary for other vendors.

New Section

This section explains the concept of administrative distance (AD) and its role in route selection when multiple routing protocols are used. It provides a list of common administrative distances for different types of routes.

Administrative Distance and Route Selection

Comparing Metrics: AD is used to select the best route before comparing metrics. A lower AD indicates higher preference for a routing protocol.

Example Scenario: When comparing routes learned from RIP and OSPF, the OSPF route will always be preferred due to its lower AD.

Common Administrative Distances

Directly connected networks: AD 0

Static routes: AD 1

External BGP (eBGP) routes: AD 20

Internal BGP (iBGP) routes: AD 200

EIGRP routes: AD 90

IGRP routes: AD 100

OSPF routes: AD 110

IS-IS routes: AD 115

RIP routes: AD 120

These values are specific to Cisco devices and may vary for other vendors.

New Section

This section emphasizes the importance of memorizing administrative distances for different routing protocols. It highlights the significance of using flashcards to aid in memorization.

Importance of Memorizing Administrative Distances

Preferred Routes: Understanding administrative distances helps determine which route will be selected when multiple routing protocols are in use.

Flashcards: Flashcards are highly recommended for memorizing administrative distances as they make the process easier.

New Section

This section presents a quiz question to reinforce understanding of how administrative distance affects route selection between different routing protocols.

Quiz Question

Route Selection: When comparing routes learned from RIP and OSPF, the OSPF route will always be added to the route table due to its lower administrative distance (AD).

The transcript does not provide a timestamp for the answer to the quiz question.

Introduction to Dynamic Routing Protocols

In this section, the instructor discusses the concept of administrative distance (AD) and how it can be used to change the preference of routing protocols and static routes. The instructor also introduces the idea of floating static routes.

Changing Administrative Distance

You can change the AD of a routing protocol to make it more or less preferred than other protocols.

This can be useful when you want OSPF routes to be preferred over EIGRP routes, for example.

The AD of a static route can also be changed.

Use the "distance metric" command when configuring a static route to set its AD.

Floating Static Routes

By changing the AD of a static route, you can make it less preferred than routes learned by dynamic routing protocols.

Ensure that the AD of the static route is higher than the AD of the routing protocol for it to work as intended.

Floating static routes are inactive unless the route learned by the dynamic routing protocol is removed.

Types of Dynamic Routing Protocols

This section covers different types of dynamic routing protocols and their classifications based on their purpose and algorithm.

Interior Gateway Protocols (IGPs) vs. Exterior Gateway Protocols (EGPs)

IGPs are used for routing within an organization, while EGPs are used for routing between organizations (e.g., over the Internet).

BGP is currently the only EGP in use.

Classification Based on Algorithm

Path vector is an algorithm used by EGPs like BGP.

Distance vector is an algorithm used by RIP and EIGRP.

Link state is an algorithm used by OSPF and IS-IS.

Metrics and Administrative Distance

This section explains the concept of metrics and administrative distance (AD) in routing protocols.

Metrics

Each routing protocol uses a different metric to determine the best route to a destination within the same protocol.

Metrics are values used to evaluate and compare routes.

Administrative Distance

Administrative distance (AD) is used to compare and select routes from different routing protocols.

AD determines the preference of one protocol over another when multiple protocols have routes to the same destination.

It is important to remember the AD values for each kind of route and routing protocol.

Review and Quiz

In this section, the instructor reviews the topics covered so far and presents a quiz.

Review

Dynamic routing protocols automatically learn routes without manual configuration.

Static routes are useful but not practical for large networks.

Different types of dynamic routing protocols include IGPs (interior gateway protocols) and EGPs (exterior gateway protocols).

Routing protocols can be classified based on their algorithm, such as distance vector or link state.

Quiz Question 1

Which route/routes will be added to the route table if R1 learns four routes to 192.168.1.0/24 through RIP, EIGRP, OSPF, and IS-IS?

Answer: Only the EIGRP route will be added because it has the lowest administrative distance among all four protocols.

Quiz Question 2

Which type of routing protocol is also known as "routing by rumor"?

Answer: Distance vector protocols operate by telling neighboring routers which routes they know, which is known as "routing by rumor."

Quiz Question 3

If R1 learns two routes to 172.16.0.0/16 via RIP, one via 10.0.0.1 and the other via 10.1.0.1, which route/routes will be entered into the routing table?

Answer: Both routes will be added to the routing table because they are learned through the same protocol.

Conclusion

The transcript covers the concept of administrative distance, changing AD for routing protocols and static routes, floating static routes, types of dynamic routing protocols (IGPs and EGPs), classification based on algorithm (distance vector and link state), metrics, and a quiz.

New Section

In this section, the speaker discusses a bonus question from Boson ExSim for CCNA related to route selection. The speaker explains the different routes shown in the output of the SHOW IP ROUTE command on RouterA and discusses which route RouterA would use to send a packet.

Route Selection Question

The speaker presents a scenario where the SHOW IP ROUTE command on RouterA displays four routes: S (static), R (RIP), D (EIGRP), and O (OSPF).

These routes have different prefix lengths, making them different destinations.

Despite having the lowest administrative distance, the static route is not necessarily the most preferred because all routes appear in the routing table.

RouterA receives a packet destined for 10.20.0.14 and needs to determine which route to use.

The options for selecting the route are:

A) RIP route with highest administrative distance

B) OSPF route with longest prefix match

C) Static route preferred over dynamic routes

D) EIGRP route with lowest administrative distance.

Answer Explanation

The speaker explains that when multiple routing protocols provide routes to the same destination, administrative distance is used to select the route.

However, in this case, since these routes are not to the same destination due to different prefix lengths, both administrative distance and metric numbers become irrelevant.

The router selects the most specific match based on longest prefix length.

Therefore, RouterA would use the OSPF route (/28) and send the packet to 192.168.10.1 via its Serial0/1 interface.

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New Section

In this section, the speaker confirms that the correct answer to the route selection question is B (the OSPF route with the longest prefix match). The speaker emphasizes the importance of understanding how routers decide which route to use when multiple entries in the routing table match a destination.

Confirmation of Correct Answer

The speaker reiterates that the correct answer is B, which states that RouterA would use the OSPF route because it has the longest prefix match.

The speaker mentions that Boson ExSim provides detailed explanations for why options A, C, and D are incorrect.

Additional reference materials on "Route selection in Cisco routers" are available online.

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New Section

In this section, the speaker concludes by thanking JCNP-level channel members and promoting supplementary materials available for further study.

Supplementary Materials and Thank You

The speaker thanks JCNP-level channel members for their support.

Supplementary materials such as flashcard decks and packet tracer practice labs are mentioned.

Viewers are encouraged to sign up for the mailing list to receive these materials.

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