CCNA 1 v3.0 Module 9TCP/IP Protocol Suite and IPAddressing
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Objectives Introduction to TCP/IP Internet addresses Obtaining an IP address
History and Future of TCP/IPThe U.S. Department ofDefense (DoD) created theTCP/IP reference modelbecause it wanted anetwork that could surviveany conditions.Some of the layers in theTCP/IP model have thesame name as layers in theOSI model.
Application Layer Handles high-level protocols, issues of representation, encoding, and dialog control. The TCP/IP protocol suite combines all application related issues into one layer and ensures this data is properly packaged before passing it on to the next layer.
Transport LayerFive basic services: Segmenting upper-layer application data Establishing end-to-end operations Sending segments from one end host to another end host Ensuring data reliability Providing flow control
Internet LayerThe purpose of the Internet layer is to sendpackets from a network node and have themarrive at the destination node independent of thepath taken.
Network Access LayerThe network access layer is concerned with all of theissues that an IP packet requires to actually make aphysical link to the network media.It includes the LAN and WAN technology details, and allthe details contained in the OSI physical and data linklayers.
Similarities of the OSI andTCP/IP ModelsBoth have layers.Both have application layers, though theyinclude very different services.Both have comparable transport andnetwork layers.Packet-switched, not circuit-switched,technology is assumed.Networking professionals need to knowboth models.
Differences of the OSI andTCP/IP ModelsTCP/IP combines the presentation and sessionlayer into its application layer.TCP/IP combines the OSI data link and physicallayers into one layer.TCP/IP appears simpler because it has fewerlayers.TCP/IP transport layer using UDP does notalways guarantee reliable delivery of packets asthe transport layer in the OSI model does.
Internet Architecture Two computers, anywhere in the world, following certain hardware, software, protocol specifications, can communicate, reliably even when not directly connected. LANs are no longer scalable beyond a certain number of stations or geographic separation.
IP AddressingAn IP address is a 32-bit sequence of 1s and 0s.To make the IP address easier to use, theaddress is usually written as four decimalnumbers separated by periods.This way of writing the address is called thedotted decimal format.
Reserved IP AddressesCertain host addressesare reserved and cannotbe assigned to deviceson a network.An IP address that hasbinary 0s in all host bitpositions is reserved forthe network address.An IP address that hasbinary 1s in all host bitpositions is reserved forthe network address.
Public and Private IPAddressesNo two machines that connect to a public network canhave the same IP address because public IP addressesare global and standardized.However, private networks that are not connected to theInternet may use any host addresses, as long as eachhost within the private network is unique.RFC 1918 sets aside three blocks of IP addresses forprivate, internal use.Connecting a network using private addresses to theInternet requires translation of the private addresses topublic addresses using Network Address Translation(NAT).
Introduction to SubnettingTo create a subnet address, a networkadministrator borrows bits from the hostfield and designates them as the subnetfield.
IPv4 versus IPv6 IP version 6 (IPv6) has been defined and developed. IPv6 uses 128 bits rather than the 32 bits currently used in IPv4. IPv6 uses hexadecimal numbers to represent the 128 bits. IPv4
Obtaining an Internet AddressStatic addressing Each individual device must be configured with an IP address.Dynamic addressing Reverse Address Resolution Protocol (RARP) Bootstrap Protocol (BOOTP) Dynamic Host Configuration Protocol (DHCP) DHCP initialization sequence Function of the Address Resolution Protocol ARP operation within a subnet
Static Assignment of IPAddressesEach individualdevice must beconfigured with anIP address.
Reverse Address ResolutionProtocol (RARP) RARP REQUEST MAC HEADER IP HEADER MESSAGE Destination Destination FF-FF-FF-FF-FF- FF 255.255.255.255 What is my IP Source address? Source FE:ED:FD:23:44:E ???????? F
BOOTP IP The Bootstrap Protocol (BOOTP) operates in a client/server environment and only requires a single packet exchange to obtain IP information. BOOTP packets can include the IP address, as well as the address of a router, the address of a server, and vendor-specific information.
Dynamic Host ConfigurationProtocol Allows a host to obtain an IP address using a defined range of IP addresses on a DHCP server. As hosts come online, contact the DHCP server, and request an address.
Problems in AddressResolutionIn TCP/IP communications, a datagram on a local-area network must contain both a destination MACaddress and a destination IP address.There needs to be a way to automatically map IPto MAC addresses.The TCP/IP suite has a protocol, called AddressResolution Protocol (ARP), which canautomatically obtain MAC addresses for localtransmission.TCP/IP has a variation on ARP called Proxy ARPthat will provide the MAC address of anintermediate device for transmission outside theLAN to another network segment.
Address Resolution Protocol(ARP)Each device on a network maintains itsown ARP table.A device that requires an IP and MACaddress pair broadcasts an ARPrequest.If one of the local devices matches theIP address of the request, it sends backan ARP reply that contains its IP-MACpair.If the request is for a different IPnetwork, a router performs a proxy ARP.The router sends an ARP response withthe MAC address of the interface onwhich the request was received, to therequesting host.