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ROUTING ANDROUTING AND

ROUTINGROUTING

PROTOCOLSPROTOCOLS

TS, PHẠM VĂN TÍNHTS, PHẠM VĂN TÍNH

PART10PART10

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ObjectiveObjective

Explain the significance of static routing Configure static and default routes Verify and troubleshoot static and default

routes Identify the classes of routing protocols Identify distance vector routing protocols Identify link-state routing protocols Describe the basic characteristics of common

routing protocols Identify interior gateway protocols Identify exterior gateway protocols Enable Routing Information Protocol (RIP) on a

router

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ROUTING BASICROUTING BASIC

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Path determinationPath determination and packet switching and packet switching

1.a path determination function 2.a switching function. The path determination function enables a router to

evaluate the available paths to a destination The network layer uses the IP routing table to send

packets from the source network to the destination network

After the router determines which path to use, it proceeds with forwarding the packet

It takes the packet that it accepted on one interface and forwards it to another interface or port that reflects the best path to the packet's destination

Routing Table Path DeterminationDetermining Network Address

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Introducing routingIntroducing routing

Routing is the process that a router uses to forward packets toward the destination network. A router makes decisions based upon the destination IP address of a packet.

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STATIC ROUTING STATIC ROUTING

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Static route operationStatic route operation

Static route operations can be divided into these three parts:

1. Network administrator configures the route

2. Router installs the route in the routing table

3. Packets are routed using the static route

ip route …

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Static Routing ExampleStatic Routing Example

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Default Routing ExampleDefault Routing Example

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Why dynamic routing is necessaryWhy dynamic routing is necessary

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Static route operationStatic route operation

Static route operations can be divided into these three parts:

1. Network administrator configures the route

2. Router installs the route in the routing table

3. Packets are routed using the static route

the administrator must configure the static route on the router using the ip route command

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Steps to configure static routes Steps to configure static routes

1. Determine all desired destination networks, their subnet masks, and their gateways. A gateway can be either a local interface or a next hop address that leads to the desired destination.

2. Enter global configuration mode. 3. Type the ip route command with a destination

address and subnet mask followed by their corresponding gateway from Step one. Including an administrative distance is optional.

4. Repeat Step three for as many destination networks as were defined in Step one.

5. Exit global configuration mode. 6. Save the active configuration to NVRAM by using

the copy running-config startup-config command.

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Configuring default route forwardingConfiguring default route forwarding

Default routes are used to route packets with destinations that do not match any of the other routes in the routing table.

Routers are typically configured with a default route for Internet-bound traffic, since it is often impractical and unnecessary to maintain routes to all networks in the Internet.

A default route is actually a special static route that uses this format: ip route 0.0.0.0 0.0.0.0 [next-hop-address |

outgoing interface]

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Verifying static route configurationVerifying static route configuration

• In privileged mode enter the command show running-config to view the active configuration.

• Verify that the static route has been correctly entered. If the route is not correct, it will be necessary to go back into global configuration mode to remove the incorrect static route and enter the correct one.

• Enter the command show ip route.

• Verify that the route that was configured is in the routing table.

•

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Show Runnig-ConfigShow Runnig-Config

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Show ip routeShow ip route

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DYNAMIC ROUTING DYNAMIC ROUTING

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Introduction to routing protocolsIntroduction to routing protocols

A routing protocol is the communication used between routers.

A routing protocol allows one router to share information with other routers.

The information a router gets from another router, using a routing protocol, is used to build and maintain a routing table. 

Examples of routing protocols are:

• Routing Information Protocol (RIP)

• Interior Gateway Routing Protocol (IGRP)

• Enhanced Interior Gateway Routing Protocol (EIGRP)

• Open Shortest Path First (OSPF)

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Dynamic routing operationsDynamic routing operations

The success of dynamic routing depends on two basic router functions:

1. maintenance of a routing table 2. timely distribution of knowledge, in the form of

routing updates, to other routers  A routing protocol defines the set of rules used

by a router when it communicates with neighboring routers. For example, a routing protocol describes:

how to send updates what knowledge is contained in these updates when to send this knowledge how to locate recipients of the updates

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Autonomous systemsAutonomous systems

An autonomous system (AS) is a collection of networks under a common administration sharing a common routing strategy. To the outside world, an AS is viewed as a single entity

The American Registry of Internet Numbers (ARIN), a service provider, or an administrator assigns an identifying number to each AS.

This autonomous system number is a 16 bit number. Routing protocols, such as Cisco’s IGRP, EIGRP require assignment of a unique, autonomous system number

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Autonomous systemsAutonomous systems

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Purpose of a routing protocol and Purpose of a routing protocol and autonomous systemsautonomous systems

The goal of a routing protocol is to build and maintain the routing table

Autonomous systems (AS) provide the division of the global internetwork into smaller and more manageable networks

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Identifying the classes of routing protocolsIdentifying the classes of routing protocols

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Distance vector routing protocol Distance vector routing protocol featuresfeatures

Distance vector routing algorithms pass periodic copies of a routing table from router to router.

Distance vector based routing algorithms are also known as Bellman-Ford algorithms.

Each router receives a routing table from its directly connected neighbor routers.

Routers discover the best path to destination networks based on the information they receive from each neighbor.

Routing table updates occur when the topology changes.

The routing tables include information about the total path cost as defined by its metric.

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Link-state routing protocol featuresLink-state routing protocol features

Link-state advertisements (LSAs) – A link-state advertisement (LSA) is a small packet of routing information that is sent between routers.

Topological database – A topological database is a collection of information gathered from LSAs.

SPF algorithm – The shortest path first (SPF) algorithm is a calculation performed on the database resulting in the SPF tree.

Routing tables – A list of the known paths and interfaces.

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Link – State ConceptsLink – State Concepts

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Linke – State Network DiscoveryLinke – State Network Discovery

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Link – State Topology ChangesLink – State Topology Changes

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Link – State ConcernsLink – State Concerns

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Comparing DV – LS RoutingComparing DV – LS Routing

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Routing ProtocolsRouting Protocols

RIP – A distance vector interior routing protocol

IGRP – Cisco's distance vector interior routing protocol

OSPF – A link-state interior routing protocol

EIGRP – Cisco’s advanced distance vector interior routing protocol

BGP – A distance vector exterior routing protocol

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Routing Information Protocol (RIP) Routing Information Protocol (RIP)

It is a distance vector routing protocol.

Hop count is used as the metric for path selection.

If the hop count is greater than 15, the packet is discarded.

Routing updates are broadcast every 30 seconds, by default.

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Interior Gateway Routing Protocol (IGRP) Interior Gateway Routing Protocol (IGRP)

Interior Gateway Routing Protocol (IGRP) is a proprietary protocol developed by Cisco.

It is a distance vector routing protocol.

Bandwidth, load, delay and reliability are used to create a composite metric.

Routing updates are broadcast every 90 seconds, by default.

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Open Shortest Path First (OSPF) Open Shortest Path First (OSPF)

Open Shortest Path First (OSPF) is a nonproprietary link-state routing protocol.

It is a link-state routing protocol.

Open standard routing protocol described in RFC 2328.

Uses the SPF algorithm to calculate the lowest cost to a destination.

Routing updates are flooded as topology changes occur.

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Border Gateway Protocol (BGP) Border Gateway Protocol (BGP)

Border Gateway Protocol (BGP) is an exterior routing protocol. The key characteristics of BGP are as follows:

It is a distance vector exterior routing protocol.

Used between ISPs or ISPs and clients.

Used to route Internet traffic between autonomous systems.