Planning and Troubleshooting Routing

and Switching

Overview

Selecting Intermediate Devices

Planning an Internet Connectivity Strategy

Planning Routing Communications

Troubleshooting TCP/IP Routing

Lesson: Selecting Intermediate Devices

Types of Devices

When to Use Routing

Types of Networking Domains

What Are the Features of Switches?

Virtual LANs

Full-Duplex Transmission in Switched Environments

Guidelines for Selecting an Appropriate Intermediate Device

Types of Devices

Device OSI layer Definition

HubPhysical (layer 1)

Extends the network by retransmitting the signalDoes not process the dataIs invisible to the nodes

SwitchData-link (layer 2)

Forwards frames according to the destination address

Uses temporary or virtual connections to connect source and destination ports

RouterNetwork (layer 3)

Used to link WANs and dissimilar LANsOperates at the packet levelSends packets based on packet addressing

Layer 3 switch

Network (layers 2 and 3)

Is a limited-purpose hardware-based IP router with bridging capabilities Also performs layer 2 switching

When to Use Routing

Use routing to:Use routing to:

Isolate networks from each other

Provide a start for a secure network implementation

Isolate networks from each other

Provide a start for a secure network implementation

Traditional uses of routersTraditional uses of routers

Connecting WANs

Segmenting LANs

Connecting WANs

Segmenting LANs

SwitchSwitch

Segment BSegment B

HubHub

Segment ASegment A

Broadcast DomainBroadcast Domain

Collision Domain BCollision Domain BCollision Domain ACollision Domain A

HubHub

Types of Networking Domains

What Are the Features of Switches?

Switch feature Benefits

Layer 3Routes packets at layer 3Forwards frames at layer 2

CostSubstantially cheaper than similar performance routers

Hardware routingFast performance (near wire speed)Minimal latency

Virtual LANs

Layer 3 SwitchLayer 3 Switch

HubHubHubHubHubHub

VLAN 1VLAN 1 VLAN 2VLAN 2

VLAN ABE – Broadcast DomainVLAN ABE – Broadcast Domain VLAN CDFG – Broadcast DomainVLAN CDFG – Broadcast Domain

A B C D E F G

Full-Duplex Transmission in Switched Environments

SwitchSwitch

Full-duplex communicationFull-duplex communication

Switched EnvironmentSwitched Environment

Frame BFrame BFrame AFrame A Frame DFrame DFrame CFrame C

Guidelines for Selecting an Appropriate Intermediate Device

Ease of implementationEase of implementation

SpeedSpeed

FunctionalityFunctionality

ProgrammabilityProgrammability

CostCost

Layer 1 supportLayer 1 support

Protocol supportProtocol support

Administration and troubleshooting sophisticationAdministration and troubleshooting sophistication

Planning an Internet Connectivity Strategy

Requirements for an Internet Connectivity Solution

NAT as a Solution for Internet Connectivity

ISA (Proxy) as a Solution for Internet Connectivity

Guidelines for Planning an Internet Connectivity Strategy

Requirements for an Internet Connectivity Solution

Internet connectivity requirementsInternet connectivity requirements

Scalability and fault tolerance

Filtering

User access

Authentication

Bandwidth control

Time-of-day access

Extensibility and flexibility

Application connectivity

Scalability and fault tolerance

Filtering

User access

Authentication

Bandwidth control

Time-of-day access

Extensibility and flexibility

Application connectivity

131.107.0.9

NAT as a Solution for Internet Connectivity

131.107.0.9

10.10.10.710.10.10.7

Why NAT is a good solution

Same security requirements for all users

Non-routed private network

Required private addressing

NAT TableNAT Table

10.10.10.0 maps to 131.107.0.910.10.10.0 maps to 131.107.0.9

10.10.10.610.10.10.6

10.10.10.1010.10.10.10

131.107.0.9

Why ISA (Proxy) is a good solution

Secure Internet and private network access Routed or non-routed network Cache web contents

ISA (Proxy) as a Solution for Internet Connectivity

IntranetIntranet

10.10.10.810.10.10.8

ISA (Proxy) ServerISA (Proxy) Server

10.10.10.0 maps to 131.107.0.910.10.10.0 maps to 131.107.0.9

10.10.10.710.10.10.7

10.10.10.910.10.10.9

10.10.10.1010.10.10.10

10.10.10.810.10.10.8

131.107.0.9

Guidelines for Planning an Internet Connectivity Strategy

Define the existing network structureDefine the existing network structure

Identify connectivity requirementsIdentify connectivity requirements

Select an appropriate solutionSelect an appropriate solution

Define security requirementsDefine security requirements

Planning Routing Communications

Determining the Appropriate Connection Method

Selecting a Routing Protocol

Guidelines for Planning Router Connectivity

Determining the Appropriate Connection Method

Connection method When used

Leased lines

Security is important Speed and reliability are required No budget constraints

Tunneling Security is important No modem infrastructure

Demand-dial routing Security is important

On demand Limited traffic Per-instance fee pricing structure

Demand-dial -persistent

Ample traffic Flat fee pricing structure

Selecting a Routing Protocol

Protocol Criteria

Static routes

Routing information rarely changes Small internetworks Scalability not an issue Manual updates required

RIP (dynamic)

Routing information constantly changes Automatic routing table updates required Existing routers use RIP Design includes demand-dial interface Maximum number of routers an IP packet will cross is 16

OSPF (dynamic)

Routing information constantly changes Existing routers use OSPF Design includes redundant paths between two subnets Design has more than 50 subnets

All other protocolsAll other protocols

ICMPICMP

Using IP Packet Filters

Branch OfficeBranch Office

Branch OfficeBranch Office

Interface A inbound

filter

Interface A inbound

filter

Interface B outbound

filter

Interface B outbound

filter

Interface C outbound

filter

Interface C outbound

filter

All protocolsAll protocols

All other protocolsAll other protocols

SNMPSNMP

Corporate HeadquartersCorporate Headquarters

Guidelines for Planning Router Connectivity

Identify the router connection methodIdentify the router connection method

Determine which connectivity options to useDetermine which connectivity options to use

Determine which routing protocol to useDetermine which routing protocol to use

Identify filter settingsIdentify filter settings

Troubleshooting TCP/IP Routing

How to Isolate a Routing Problem

When to Use Each of the Troubleshooting Tools

Troubleshooting TCP/IP Routing

How to Isolate a Routing Problem

Inside-Out StrategyInside-Out StrategyOutside-In StrategyOutside-In Strategy

Can you ping the

remote host?

Can you tracert to

remote host?

Can you access the

failed system?

If problem still exists, check route configuration

Contact the administrator

of the failed system

Check system configuration

Fix configuration

problem

Determine where trace

fails

YesYes

No No

Yes

No

Is the IP configuration

correct?

Correct the configuration

Use tracert to identify

communication breakdown

No

Is the routing table

accurate?

Correct/delete the incorrect route entries

Contact network support engineer

Can you ping the gateway?

Can you ping interior gateways?

No

No

No

Yes

Yes

Yes

Divide-by-Half : Isolate by ½ the connection issue, then isolate by ½ againDivide-by-Half : Isolate by ½ the connection issue, then isolate by ½ again

When to Use Each of the Troubleshooting Tools

Troubleshooting area Utility to use

Local computer configuration

HostnameIpconfigNetStatNbtstatARP

Network connections NetDiag

Tracing paths

TracertPingPathping

DNS NSlookup