CCNA2 M6 Routing and Routing Protocols

8/14/2019 CCNA2 M6 Routing and Routing Protocols

1/23

CCNA Semester2

Module 6

Routing and Routing Protocols

Objectives

Introduction to static routing

Dynamic routing overview

Routing protocols overview


2/23

Introduction to Static Routing

Introducing 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.

In order to make the correct decisions, routers

must learn the direction to remote networks.


3/23

Route Types

The Administrative Distance

AD is a rating of the trustworthiness of a

routing information source, expressed as a

numeric value from 0 to 255. The higher the

number, the lower the trustworthiness

rating.

Example: Directed connection 0 Static route (by default) 1

IGRP 100

OSPF 110

RIP 120


4/23

Static route

Advantages:

Require very little maintenance on small networks

No network overhead May hide parts of networks

Disadvantages:

Require a tremendous amount of administrative time on

large networks

Lack scalability

The IP ROUTE command

ip route network [ mask] { address | interface } [ distance ][ permanent ]

ip route network [ mask ] { address | interface } [ distance ][ permanent ]

Router (config)#

Defines a path to an IP destination network or subnet

ip route command Description

network destination network

mask dest. network mask

address IP address of next hop

permanent if set, route will not be removed when intf. is

shutdown

interface Name of interface to get to destination

distance Administrative distance


5/23

Static route command

AD in static route

A route with a lower AD will be installed before

an identical route with a higher AD.

The default AD when using next-hop address is

1, while the default AD when using the outgoing

interface is 0.

If an administrative distance other than thedefault is desired, a value between 0 and 255 is

entered


6/23

Route in Routing Table

If the router cannot reach the outgoing interfacethat is being used in the route, the route will notbe installed in the routing table.

This means if that interface is down, the routewill not be placed in the routing table

To hold the route in routing table even ifassociated outgoing interface is down, usepermenent parameter.

Default Route

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 forInternet-bound traffic.

ip route 0.0.0.0 0.0.0.0 [next-hop-address | outgoing

interface]


7/23

Using the DEFAULT IP ROUTE command

Verifying static route configuration

show running-config to verify that the static route

was entered correctly.

show ip route command to make sure that the

static route is present in the routing table.


8/23

Troubleshooting static route configuration

Show ip route command

Ping command

Traceroute command

Dynamic Routing Overview


9/23

Routed Protocol

A routed protocol is used to direct user traffic.

A routed protocol provides enough information

in its network layer address to allow a packet tobe forwarded from one host to another based onthe addressing scheme.

Examples of routed protocols are: Internet Protocol (IP)

Internetwork Packet Exchange (IPX)

Routing Protocol

A routing protocol is the communication used betweenrouters.

A routing protocol allows one router to shareinformation with other routers regarding the networks itknows about.

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)


10/23

Autonomous systems

An autonomous system (AS) is a collection of networks under a

common administration sharing a common routing strategy.

The American Registry of Internet Numbers (ARIN), a service

provider, or an administratorassigns an identifying number to eachAS.

This autonomous system number is a 16 bit number.

Purpose of a routing protocol

The goal of a routing protocol is to build and

maintain the routing table.

This table contains the learned networks and

associated ports for those networks.


11/23

Updating route

The routing protocol learns all available routes, places

the best routes into the routing table, and removes

routes when they are no longer valid.

The network knowledgebase needs to reflect an

accurate consistent view of the current topology.

Convergence

When all routers in an internetwork are operating with

the same routing knowledge, the internetwork is said to

have converged.

During convergence, problems may occur like: routing

loops, inconsistent traffic forwarding, inconsistent

routing table entries.

Fast convergence is desirable because it reduces theperiod of time in which routers would continue to make

incorrect routing decisions.


12/23

Classes of routing protocols

Most routing algorithms can be classified into one oftwo categories:

distance vector

link-state

Distance vector algorithm

Pass periodic routing update (copies of arouting table) from router to router.

These regular updates between routerscommunicate topology changes.

Each router receives a routing table from its

directly connected neighbors. Distance-vector algorithms do not allow a

router to know the exact topology of aninternetwork.


13/23

Distance Vector Discovery

Link-State Routing

Also known as Dijkstras algorithm or as SPF

(shortest path first) algorithms.

Link-state routing algorithms maintain a

complex database of topology information

A link-state routing algorithm maintains full

knowledge of distant routers and how theyinterconnect.


14/23

Link-State Concepts

Link-State Concerns


15/23

Distance Vector vs. Link State

Routing Protocols Overview


16/23

Router Functions

A router has two basic functions: Path determination occurs at the network layer, enables a

router to evaluate the paths to a destination

Switching function is the internal process used by a routerto accept a packet on one interface and forward it to asecond interface on the same router.

Communicate Path Information


17/23

Addressing: Network and Host

Network address: Used to determine path to a network

Host address: Specifies specific port or device on a network

How distances are determined

Primary objective of routing protocol is todetermine the best route to put in therouting table.

Each routing algorithm interprets what isbest in its own way.

Routing algorithm generates a number,called the metric value, for each paththrough the network.

Typically, the smaller the metric number, thebetter the path.


18/23

Distance in Metrics

The router and network Commands


19/23

IP Routing Configuration Tasks

Routing protocols


20/23

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.

Interior Gateway Routing Protocol (IGRP)

Cisco proprietary protocol

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.


21/23

Open Shortest Path First (OSPF)

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.

Enhanced-IGRP (EIGRP)

Cisco proprietary protocol

It is an enhanced distance vector routing protocol.

Uses load balancing.

Uses a combination of distance vector and link-state

features.

Uses Diffused Update Algorithm (DUAL) to calculate theshortest path.

Routing updates are broadcast every 90 seconds or as

triggered by topology changes.


22/23

Border Gateway Protocol (BGP)

Exterior routing protocol.

It is a distance vector exterior routing protocol.

Used between ISPs or ISPs and clients.

Used to route Internet traffic between

autonomous systems.

Summary

Configure static route, default route, float staticroute

Protocol administrative distance

Routed and routing protocol

Distance vector and link state routing protocol

Router functions Routing protocols metrics

IP routing configuration tasks


23/23

Lab Topology

Lab_A

Lab_B

Lab_C

S0/1

S0/1

S0/0

F0/0

S0/1

F0/0

Lab_D

Lab_E

Lab_F

S0/0

S0/1

S0/0

F0/0

S0/1

F0/0

F0/0 F0/0

S0/1S0/0

Port Lab_A Lab_B Lab_C Lab_D Lab_E Lab_F

S0/0 N/A 199.6.13.1/24 204.204.7.1/24 142.18.0.1/16

204.204.7.2/24

192.168.1.1/24

34.10.120.1/16 N/A

S0/1 201.10.11.1/24 201.10.11.2/24 199.6.13.2/24 142.18.0.2/16 34.10.210.5/16

F0/0 172.16.11.1/24 10.0.0.1/8 172.16.11.2/24 10.0.0.2/8 192.168.1.2/24

CCNA2 Module6

Documents

CCNA2 M6 Routing and Routing Protocols