09-1-IP Routing

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IP Routing

The Purpose and Properties of

Routing

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At the end of this lesson you will be

able to:

Explain the purpose and properties of routing

Network+ 2009 Exam objective 1.6

What we will cover

What is Routing?

Static and Dynamic Routing Protocols

Routing vs. Routed Protocols

Interior Gateway Protocols and Exterior

Gateway Protocols The Next Hop

Routing tables

Convergence

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Gateways vs. Routers

Gateway Router

What is Routing?

The process that a router uses to forward

packets toward the destination network.

A router makes this decision based on the

network part of the destination IP address

Before making that decision the router must

have the correct information

How does it get that information?

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Static vs. Dynamic Routing Protocols

Static

Routes enteredmanually

Dynamic

Use Routing Protocols

RIP

v1 &v2

I

GR

P

E

I

G

R

P

O

SP

F

I

S

-

I

S

B

G

P

Static Routing

S0

192.168.0.1

192.168.30.0 192.168.20.0 192.168.10.0

192.168.0.2

S0192.168.1.2

S0

S1

192.168.1.1

ip route 192.168.30.0 255.255.255.0 192.168.0.1

E0 E0

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ip route 0.0.0.0 0.0.0.0 190.16.20.2

Setting the Default Gateway on a

Router

192.168.20.x

255.255.255.0

Default GW: 192.168.20.1

190.16.20.2

192.168.20.1/24 190.16.20.1/30

ISP

Routed Protocols vs. Routing Protocols

Routed protocols

Carry user data on the

network.

examples: IP, IPX,Appletalk

Routing protocols

Exchange information

about routes betweenRouters.

examples: RIP, IGRP,EIGRP, OSPF, IS-IS, BGP

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IGP vs. EGP

Interior Gateway Protocols

Within Autonomous Systems

Exterior Gateway Protocols

Between Autonomous Systems

What is an Autonomous System

ISP M

ISP Z

ISP C

Autonomous

System 50

ISP D

ISP W

ISP A

ISP K

Autonomous

System 235

Exterior Routing

A collections of networks

Under the control of one or more Network Operators

With a common Internet routing policy

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Interior and Exterior Routing Protocols

Interior Gateway Protocols

RIP

OSPF

IGRP

EIGRP

IS-IS

Exterior Gateway Protocols

BGP

Routing Table determines how to getto Destination Networks

172.16.20.0/24 172.20.30.0/24 10.10.10.0/24

.2 .1 .1 .2

192.168.20.0/24 192.168.30.0/24

Network Next Hop Exit Interface Metric

172.16.20.0/24 192.168.20.2 E1 1

172.20.30.0/24 Directly Connected E0 0

10.10.10.0/24 192.168.30.2 E2 1



E1E0

E1 E1

E0 E0

E2

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Next Hop

172.16.20.0/24 172.20.30.0/24 10.10.10.0/24

.2 .1 .1 .2

192.168.20.0/24 192.168.30.0/24

Network Next Hop Exit Interface Matrix


172.20.30.0/24 192.168.20.1 E1 1

10.10.10.0/24 192.168.20.1 E1 2


192.168.30.0/24 192.168.20.1 E1 1

E1E0

E1 E1

E0 E0

E2

What is Convergence (steady state)?

http://commons.wikimedia.org/wiki/File:Kam

akura-buddha-7.jpg

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Summary

What is Routing?

Static and Dynamic Routing Protocols

Routing and Routed Protocols

IGP and EGP

The Next Hop

The Routing Table

Convergence

Common IPv4 Routing Protocols

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At the end of this lesson you will be

able to:

Identify common IPv4 routing protocols


What we will cover

Distancevector

RIP RIPv2

Linkstate

OSPF IS-IS

Hybrid EIGRP

BGP

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Routing Protocols work in different

ways

Types ofRouting

ProtocolsLinkState

DistanceVector Hybrid

PathVector

Routing Decision Tree

WhichRouting

Protocol?

Static

Dynamic

IGP

DistanceVector

Link State

Hybrid

EGP BGP

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Distance Vector Routing Protocols

The Meaning of Distance Vector

A router using Distance Vector Routing

Protocols knows two things:

Vector, or Direction, traffic

should be directed

Distance to final destination

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Distance Vector Routers Exchange

Routing Table with Neighbours

Use neighbours routes to build its Routing Table

Characteristics of Distance Vectorrouting protocols

Pro

Simple implementationand maintenance

Use relatively littlesystem resources

Con

Does not scale well

Slow Convergence

Routing Loop

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Initial Network Discovery

Router B

receivesinformation

from Router A.

Router B adds adistance vector

number (suchas a number ofhops), whichincreases the

distance vector.

Then Router Bpasses this new

routing table toits otherneighbor,Router C.

This same step-by-step process

occurs in alldirectionsbetweenneighborrouters.

Network Updates are exchangedNeighbour to Neighbour

Topology Change

occurs

Router A sends

out its updatedRouting Table

Router B

Update its

Routing Table

AB

Router A

Update its

Routing Table

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PROCESS OF CONVERGENCE

At the start a routers only know abouttheir own networks

10.1.0.0 10.2.0.0 10.3.0.0 10.4.0.0

E0 S0 S0 S1 S1 E0

Network Interface Hop

10.1.0.0 E0 0

10.2.0.0 S0 0


10.3.0.0 S1 0

10.4.0.0 E0 0


10.2.0.0 S0 0

10.3.0.0 S1 0

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After the first update cycle, router

learn from their neighbours

10.1.0.0 10.2.0.0 10.3.0.0 10.4.0.0

E0 S0 S0 S1 S1 E0


10.1.0.0 E0 0

10.2.0.0 S0 0

10.3.0.0 S0 1


10.2.0.0 S1 1

10.3.0.0 S1 0

10.4.0.0 E0 0


10.1.0.0 S0 1

10.2.0.0 S0 0

10.3.0.0 S1 0

10.4.0.0 S1 1

After the next update, network is fullyconverged

10.1.0.0 10.2.0.0 10.3.0.0 10.4.0.0

E0 S0 S0 S1 S1 E0


10.1.0.0 E0 0

10.2.0.0 S0 0

10.3.0.0 S0 1

10.4.0.0 S0 2


10.1.0.0 S1 2

10.2.0.0 S1 1

10.3.0.0 S1 0

10.4.0.0 E0 0


10.1.0.0 S0 1

10.2.0.0 S0 0

10.3.0.0 S1 0

10.4.0.0 S1 1

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Problems and Solutions with Distance-

Vector Routing Protocols

Problems

Count to infinity

Routing Loops

Solutions

Set maximum hop count

Split horizon

Poison reverse

Hold-down timers

Router Information Protocol (RIP)

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RIP v1 Characteristics

Classful

Distance Vector

Metric = hop count

Routes with a hop count > 15 are unreachable

Broadcast updates every 30 seconds

UDP port 520

Easy to Configure, Low Overheads

RIP v2 Characteristics

Classless

Distance Vector

Metric = hop count

Routes with a hop count > 15 are unreachable

Multicast updates every 30 seconds

UDP port 520

Easy to Configure, Low Overheads

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Configuring RIP

Configuring RIP

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RIPv1 vs. RIPv2

RIPv1 RIPv2

Distance Vector Distance Vector

Maximum hop count of 15 Maximum hop count of 15

Classful Classless

Broadcast Based Uses multicast 224.0.0.9

No support for VLSM Supports VLSM

No Authentication Allows MD5 Authentication

No support fordiscontiguous networks

Supports discontiguousnetworks

Comparing RIPv1 and RIPv2 Messages

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Link State Routing Protocols

Link State Routing Protocols

Also known as Shortest Path First

Based on DijkstrasSPF algorithm

Two Main Protocols OSPF

IS-IS

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Topological Map

SPF

Algorithm

SPF Tree

This Router

Link State Updates

The Shortest Path First Process

1. Collect LinkState

Updates

2. Build Link

State

Database

3. Run SPF

Algorithm

4. Find the ShortestPath to all

Networks from

THIS Router

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OSPF Features

Both memory and processor intensive

Can scale to large networks

Fast convergence

No routing loops

Intermediate System to IntermediateSystem (IS-IS)

Link State

RoutingProtocol

InteriorGatewayRoutingProtocol

Usually

used bylarge ISPs

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Features of IS-IS

Two Level Hierarchy

L1 Level 1

routes withinan area.

L2 Level 2routes

between areasand other AS

UsesConnectionless

NetworkService (CLNS)for data packet

deliverybetweenrouters.

ISO standard10589

RFC 1195defines

Integrated IS-IS(CLNS and IP)

Hybrid Routing Protocols

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Enhanced Interior Gateway Routing

Protocol (EIGRP)

Advanced Distance Vector or Hybrid

Cisco proprietary

Combines the advantages of Link-Stateand Distance Vector routing protocols

Fast Convergence

Very Scalable

Complex Matrix (Bandwidth and Delay)

Path Vector Routing Protocols

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The Border Gateway Protocol is the

Internet Routing Protocol

The Exterior Gateway Protocol

Routes between Autonomous Systems

Path Vector

Currently Version 4

Interior Gateway Protocol Comparison

Feature RIPv1 RIPv2 EIGRP OSPF IS-IS

Classless No Yes Yes Yes Yes

Supports VLSM No Yes Yes Yes Yes

Sends Mask In Update No Yes Yes Yes Yes

Distance Vector Yes Yes Hybrid No No

Link-state No No Hybrid Yes Yes

Supports Autosummarization No Yes Yes No No

Supports Manual Summarization No Yes Yes Yes Yes

Proprietry No No Yes No No

IP Multicast Routing Updates No Yes Yes Yes -

Support Authentication No Yes Yes Yes Yes

Convergence Speed Slow Slow Very Fast Fast Fast

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IPv6 Routing Protocols

At the end of this lesson you will beable to:

Identify common IPv4 and IPv6 routing

protocols


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What we will cover

Distancevector

RIPng

Linkstate

OSPF IS-IS

Hybrid EIGRP

BGP

IPv6 Routing Protocols

IPv6 routing types:

Static

RIPng (RFC 2080)

OSPFv3 (RFC 2740) IS-IS for IPv6

MP-BGP4 (RFC 2545/2858)

EIGRP for IPv6

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RIP for IPv6 is named RIPng

Same as IPv4:

Distance-vector, radius of 15 hops, split-horizon, and

poison reverse

Based on RIPv2

Updated features for IPv6:

IPv6 prefix, next-hop IPv6 address

Uses the multicast group FF02::9, as the destination

address for updates

Uses IPv6 for transport

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OSPF Version 3 (OSPFv3) is similar toOSPF for IPv4

Same mechanisms, but a major rewrite of the

protocol

Updated features for IPv6:

Every IPv4-specific semantic is removed

Carry IPv6 addresses

Link-local addresses used as source

IPv6 transport

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EIGRPv6 is similar to EIGRP for IPv4

Uses multicast address ff02::A (EIGRP on IPv4uses 224.0.0.10)

Router(config)# ipv6 router eigrp10

Router(config-rtr)# no shutdown

under the interface

Router(config-if)# ipv6 eigrp 10

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Summary

Static

RIPng

OSPFv3

IS-IS for IPv6

MP-BGP4

EIGRP for IPv6

09-1-IP Routing

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