ip routing & switching basics module - 1

8/8/2019 IP Routing & Switching Basics Module - 1

1/55

IP Routing & SwitchingBasicsModule - 1

By: Muhammad AhsanKhan


2/55

Session Details:

Theory :

TCP/IP Concepts

IP Addressing

Sub-netting

NAT/PATIP Routing concepts (Static , Dynamic)

RIP

GRE/IPSec


3/55

TCP/IP Concepts


4/55

OSI

Open Systems Interconnection

Developed by the International

Organization for Standardization (ISO)Seven layers

A theoretical system

TCP/IP is the de facto standard


5/55

OSI - The Model

A layer model

Each layer performs a subset of the

required communication functionsEach layer relies on the next lower layer toperform more primitive functions

Each layer provides services to the nexthigher layer

Changes in one layer should not requirechanges in other layers


6/55

66

OSI Layers

It is use to guide productimplementers so that theirproducts will consistently workwith other products.


7/55

The OSI Environment


8/55

TCP/IP ProtocolArchitecture

Developed by the US DefenseAdvanced Research Project Agency

(DARPA) for its packet switchednetwork (ARPANET)

Used by the global Internet

No official model but a working one.Application layer

Host to host or transport layer


9/55

Physical Layer

Physical interface between datatransmission device (e.g. computer)

and transmission medium or networkCharacteristics of transmissionmedium

Signal levelsData rates

etc.


10/55

Network Access Layer

Exchange of data between end systemand network

Destination address provisionInvoking services like priority


11/55

Internet Layer (IP)

Systems may be attached to differentnetworks

Routing functions across multiplenetworks

Implemented in end systems and

routers


12/55

Transport Layer (TCP)

Reliable delivery of data

Ordering of delivery


13/55

Application Layer

Support for user applications

e.g. http, SMPT


14/55

OSI v TCP/IP


15/55

TCP

Usual transport layer is Transmission Control Protocol

Reliable connection

Connection

Temporary logical association between entities in different systems

TCP PDU

Called TCP segment

Includes source and destination port (c.f. SAP)

Identify respective users (applications)

Connection refers to pair of ports

TCP tracks segments between entities on each connection


16/55

UDP

Alternative to TCP is User DatagramProtocol

Not guaranteed deliveryNo preservation of sequence

No protection against duplication

Minimum overhead

Adds port addressing to IP


17/55

TCP and UDP Headers


18/55

IP and IPv6

IP (v4) header minimum 20 octets (160bits)

32-bit source and destinationaddresses

Checksum applies to header to avoidincorrect delivery

Protocol field shows if TCP, UDP etc.carried

Flags and fragmentation offset used infragmentation


19/55

IPv4 Header


20/55

TCP/IP Concepts


21/55

2121

Action of

Sender


22/55

Action of Router


23/55

2323

Action ofReceiver


24/55

IP Addressing


25/55

An IP (Internet Protocol) address is aunique identifier for a node or hostconnection on an IP network.

An IP address is a 32 bit binary numberusually represented as 4 decimal values,

each representing 8 bits, in the range 0 to255 (known as octets) separated bydecimal points. This is known as "dotteddecimal notation.


26/55

Address Classes

There are 5 different address classes.You can determine which class any IPaddress is in by examining

the first 4 bits of the IP address.

Class A addresses begin with0xxx, or 1 to 126 decimal.

Class B addresses begin with10xx, or 128 to 191 decimal.


27/55


28/55

Subnetting

Subnetting an IP Network can be donefor a variety of reasons, includingorganization, use of different

physical media (such as Ethernet,FDDI, WAN, etc.), preservation ofaddress space, and security. The

most common reason is to controlnetwork traffic. In an Ethernetnetwork, all nodes on a segment seeall


29/55

Subnet Masking

Applying a subnet mask to an IPaddress allows you to identify thenetwork and node parts of the address.Performing a bitwise logical ANDoperation between the IP address andthe subnet mask results in the Network

Address or Number.

For example, using our test IP addressand the default Class B subnet mask,

we get:


30/55

NAT/PAT


31/55

Network AddressTranslation (NAT)In computer networking, network address translation (NAT) isthe process of modifying network address information in datagram(IP) packet headers while in transit across a traffic routing devicefor the purpose of remapping one IP address space into another.

Most often today, NAT is used in conjunction with networkmasquerading (or IP masquerading) which is a technique thathides an entire IP address space, usually consisting ofprivatenetwork IP addresses (RFC 1918), behind a single IP address inanother, often public address space. This mechanism isimplemented in a routing device that uses shameful translation

tables to map the "hidden" addresses into a single IP address andthen readdresses the outgoing Internet Protocol (IP) packets on exitso that they appear to originate from the router. In the reversecommunications path, responses are mapped back to theoriginating IP address using the rules ("state") stored in thetranslation tables. The translation table rules established in this

fashion are flushed after a short period without new trafficrefreshing their state.


32/55

Basic NAT and PAT

There are two levels of network addresstranslation.

Basic NAT: This involves IP addresstranslation only, not port mapping.

PAT (Port Address Translation). Alsocalled simply "NAT" or "Network Address

Port Translation, NAPT". This involves thetranslation of both IP addresses and portnumbers.

All Internet packets have a source IP


33/55

Benefits

The primary benefit ofIP-masquerading NAT is thatit has been a practical solution to the impendingexhaustion of IPv4 address space. Even largenetworks can be connected to the Internet with as

little as a single IP address. The more commonarrangement is having machines that require end-to-end connectivity supplied with a routable IP address,while having machines that do not provide services tooutside users behind NAT with only a few IP addressesused to enable Internet access.

Some[have also called this exact benefit a majordrawback, since it delays the need for theimplementation of IPv6, quote:

"


34/55

IP Routing


35/55

Why Routing?


36/55

Routed vs Routing

Routed Protocol:

IP, IPX.

Routing Protocol:

RIP, EIGRP, OSPF, BGP.


37/55

Static/Dynamic Routing

Static

Simple

Doesnt provide optimal routing andfast convergence (*IP SLA)

Dynamic

More Complex

Provide optimal routing and fast

convergence dynamically

l f l d l l


38/55

Classful and Classless

Classful:

Follows bit boundaries of Class A,BandC

Routing Protocols:

RIP, EIGRP

Example: If we configured 10.10.100.0/24, it would

advertise it as a CLASS A (10.0.0.0/8) address.

Classless:

d i i i i


39/55

Administrative Distance(AD)

Used to determine which routing protocolwould inject best route in the Routing Table.

Lowest Administrative Distance between two

routing protocols would WIN.

Protocol AD:

If EIGRP & OSPF both learning 10.10.100.0/24,

preference would be given to?

T f D i


40/55

Types of DynamicRouting

Distance Vector

Advertise full routing table, no

neighbor or topology table.Example: Appletalk RTMP, IPX RIP, IPRIP , IGRP

Link State

Maintain neighbor and topology table

Advertise routing table


41/55

Routing InformationProtocol (RIP)

R ti I f ti


42/55

Routing InformationProtocol (RIP)

The Routing Information Protocol(RIP) is a dynamic routing protocolused in local and wide area networks.

Interior Gateway Protocol (IGP)

RIP Version 1 - RFC 1058 (1988)

RIP Version 2 (RFC 2453)

RIP v1 / RIP v2 (Classful/Classless)

RIP has also been adapted for use in

T h i l D t il


43/55

Technical Details

Routing Type: Distance Vector

Algorithm : Bellman Ford

Metric: HOPS (hop count as a routing metric)

Hop Limits: 15

Updates: Send full updates after every 30 seconds.

Administrative Distance: 120

Other: Routing Table Symbol (R)

T h i l D t il


44/55

Technical Details(contd)

The maximum number of hops allowedfor RIP is 15. This hop limit, however,also limits the size of networks that RIPcan support

A hop count of 16 is considered aninfinite distance and used to deprecateinaccessible, inoperable, or otherwiseundesirable routes in the selectionprocess.

RIP im lements the s lit horizon

S lit H i


45/55

Split Horizon

split-horizon route advertisementis a method of preventing routing loopsin distance-vector routing protocols byprohibiting a router from advertising aroute back onto the interface fromwhich it was learned.

C fi i RIP


46/55

Configuring RIP

RIP Detailed configuration will becovered in LAB, some basiccommands:

RIP F t S


47/55

RIP Feature Summary


48/55

Generic RoutingEncapsulation (GRE)


49/55

St t f GRE


50/55

Structure of a GREEncapsulated Packet

GRE Header


51/55

GRE Header

Checksum Present (bit 0)If the Checksum Present bit is set to one, then the Checksum and the

Reserved1 fields are present and the Checksum field contains validinformation. Note that a compliant implementation MUST accept andprocess this field.Reserved0 (bits 1-12)A receiver MUST discard a packet where any of bits 1-5 are non-zero,unless that receiver implements RFC 1701. Bits 6-12 are reserved for

future use. These bits MUST be sent as zero and MUST be ignored onreceipt.Version Number (bits 13-15)The Version Number field MUST contain the value zero.Protocol Type (2 octets)The Protocol Type field contains the protocol type of the payload packet.

These Protocol Types are defined in [RFC1700] as "ETHER TYPES" and inETYPES . An im lementation receivin a acket containin a Protocol


52/55

Checksum (2 octets)The Checksum field contains the IP (one's complement) checksum sum ofthe all the 16 bit words in the GRE header and the payload packet. Forpurposes of computing the checksum, the value of the checksum field iszero. This field is present only if the Checksum Present bit is set to one.Reserved1 (2 octets)The Reserved1 field is reserved for future use, and if present, MUST betransmitted as zero. The Reserved1 field is present only when theChecksum field is present (that is, Checksum Present bit is set to one).IPv4 as a PayloadWhen IPv4 is being carried as the GRE payload, the Protocol Type fieldMUST be set to 0x800.

Why GRE?


53/55

Why GRE?

Configuring GRE


54/55

Configuring GRE

Will be covered in LAB session

Topics will be covered in


55/55

Topics will be covered inModule - 2

VLAN

Trunking

Switching in CYBERNET

ip routing & switching basics module - 1

Documents