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COMPUTER NETWORKS- ROUTING & SWITCHING [CCNA]

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COMPUTER NETWORKS-ROUTING & SWITCHING [CCNA]

COMPANY PROFILE: TCIT-IT

Telecommunications Consultants India Ltd (TCIL) is a leading ISO - 9001:2000 certified public sector undertaking. TCIL, a premier telecommunication consultancy and engineering company with a strong base in Telecommunication & Information Technology (IT).

It was incorporated in 1978 by Department of Telecommunications (DOT), Government of India under the aegis of Ministry of Communications, headed by Minister of Communications and Information Technology.The Organizational Structure is formed with the objectives of providing globally world-class technology and Indian expertise in all fields of Telecommunications and to provide total Quality management & excellence in project execution.

TCIL-IT is managed byICSIL(Intelligent Communication Systems India Ltd.), a Joint Venture of TCIL (Telecommunication Consultants India Ltd), a Govt. of India Enterprise and DSIIDC (Delhi State Industrial Infrastructure Development Corporation Ltd). TCIL-IT has tie-up with many government agencies to impart computer education for career advancement.

There are a number of PSUs under DoT. TCIL is one of them. Some other major companies are

1. Bharat Sanchar Nigam Limited (BSNL)

2. Mahanagar Telephone Nigam Limited (MTNL) 3. ITI Limited

TCIL has its presence in almost 45 Countries mainly in Middle East Africa, South-East Africa, South-East Asia and Europe.

COMPUTER NetworksComputer network : A collection of computing devices that are connected in various ways in order to communicate and share resources.Usually, the connections between computers in a network are made using physical wires or cables. However, some connections are wireless, using radio waves or infrared signals.

The purpose of a network is to share resources-A resource may be:-A file-A folder-A printer-A disk drive-Or just about anything else that exists on a computer.

1. Network designa. Peer-to-peerb. Server/Client

2. Area networkPAN(Personal Area Network)LAN(Local area network)W-LAN(Wireless LAN)CAN(Campus Area network)SAN(Storage data area network)GAN(Global area network) Components of Networks

Network topologyStar Topology:Ring TopologyMesh TopologyTree TopologyHybrid Topology3.3.iv. Network Protocols3.3.v. Wired and wireless

1. Network DesignPeer-to-Peer: apeer-to-peerorP2Pnetwork, the tasks are allocated among all the members of the network. There is no real hierarchy among the computers, and all of them are considered equal. This is also referred to as a distributed architecture or workgroup without hierarchy. A peer-to-peer network does not use a central computer server that controls network activity. Instead, every computer on the network has a special software running that allows for communications between all the computers.

Server Client: In aclient/servernetwork, a number of network clients or workstations request resources or services from the network. One or more network servers manage and provide these resources or services. The clients are computers that depends on the server for data and software. Network servers are also referred to as computer servers or simply servers. Sometimes a server is described in terms of the specific service it provides, such as e-mail server, print server or storage server.

2. Types of Networking1. LAN It stands for local area network. Location: In a building or individual rooms or floors of buildings or connecting nearby buildings together like a campus wide network like a college or university.2. MAN It stands for metropolitan area network. Location: network connecting various cities.

3. WAN It stands for wide area network. This communication system links LANs between cities, countries and continents. The main difference between a MAN and a WAN is that the WAN uses Long Distance Carriers rather than Local Exchange carriers. Location: City to city, across a country or across a continent. Wide Area Networks (WANs) connect LANs together between cities or across a country.

3. Network Topologya) BUS Topology: All the nodes (file server, workstations, and peripherals) on a bus topology are connected by one single cable. Advantages of Bus Topology It is Cheap, easy to handle and implement. Require less cable It is best suited for small networks.Disadvantages of Bus Topology The cable length is limited. This limits the number of stations that can be connected. This network topology can perform well only for a limited number of nodes.b) RING Topology In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction. A failure in any cable or device breaks the loop and can take down the entire network.

Advantage of Ring Topology Very orderly network where every device has access to the token and the opportunity to transmit. Easier to Manage than a Bus Network. Good Communication over long distances. Handles high volume of traffic.Disadvantages of Ring Topology The failure of a single node of the network can cause the entire network to fail. The movement or changes made to network nodes affects the performance of the entire network.

c) STAR Topology In a star network, each node (file server, workstations, and peripherals) is connected to a central device called a hub. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. Data on a star network passes through the hub, switch, or concentrator before continuing to its destination.

Advantages of Star Topology Easy to manage Easy to locate problems (cable/workstations) Easier to expand than a bus or ring topology. Easy to install and wire. Easy to detect faults and to remove parts.Disadvantages of Star Topology Requires more cable length than a linear topology. If the hub or concentrator fails, nodes attached are disabled. More expensive because of the cost of the concentrators.

d) TREE Topology A tree topology (hierarchical topology) can be viewed as a collection of star networks arranged in a hierarchy. This tree has individual peripheral nodes which are required to transmit to and receive from one other only and are not required to act as repeaters or regenerators

Advantages of a Tree Topology Point-to-point wiring for individual segments. Supported by several hardware and software vendors. All the computers have access to the larger and their immediate networks.Disadvantages of a Tree Topology Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies.

e) MESH Topology In this topology, each node is connected to every other node in the network. Implementing the mesh topology is expensive and difficult. In this type of network, each node may send message to destination through multiple paths.

Advantage of Mesh Topology No traffic problem as there are dedicated links. It has multiple links, so if one route is blocked then other routes can be used for data communication. Points to point links make fault identification easy. Disadvantage of Mesh Topology There is mesh of wiring which can be difficult to manage. Installation is complex as each node is connected to every node. Cabling cost is high.f) HYBRID Topology A combination of any two or more network topologies. A hybrid topology always accrues when two different basic network topologies are connected. It is a mixture of above mentioned topologies. Usually, a central computer is attached with sub-controllers which in turn participate in a variety of topologies.

Advantages of a Hybrid Topology It is extremely flexible. It is very reliable. Disadvantages of a Hybrid Topology Expensive

NETWORKING DEVICESHUBThe hubs used on UTP Ethernet networks are repeaters as well, but they can have many RJ45 ports instead of just two BNC connectors. When data enters the hub through any of its ports, the hub amplifies the signal and transmits it out through all of the other ports. BRIDGESA bridge is used to join two network segments together, it allows computers on either segment to access resources on the other. They can also be used to divide large networks into smaller segments. ROUTERS Routers are networking devices used to extend or segment networks by forwarding packets from one logical network to another. Routers are most often used in large internetworks that use the TCP/IP protocol suite and for connecting TCP/IP hosts and local area networks (LANs) to the Internet using dedicated leased lines.

BROUTERSBrouters are a combination of router and bridge. This is a special type of equipment used for networks that can be either bridged or routed, based on the protocols being forwarded. Brouters are complex, fairly expensive pieces of equipment and as such are rarely used. NICs (Network Interface Card)Network Interface Card, or NIC is a hardware card installed in a computer so it can communicate on a network. WAPs (Wireless Access Point)Access points act as wireless hubs to link multiple wireless NICs into a single subnet. Access points also have at least one fixed to allow the wireless network to be bridged to a traditional wired Ethernet network.

MODEMSA modem is a device that makes it possible for computers communicate over telephone lines. The word modem comes from Modulate and Demodulate.

SWITCHESSwitches are a special type of hub that offers an additional layer of intelligence to basic, physical-layer repeater hubs.

NETWORKING CABLESCoaxial Cable Coaxial cable is braided-grounded strands of wire that can provide some shielding and noise immunity; however, the installation and the termination of the cable itself can be costly. Coaxial cabling, which uses connectors called BNC (Bayonet Nut Connector) is known as, in forms of Ethernet, thick net and thin net, in the older LAN technology, ARC net, and cable TV. Fiber Optic Fiber optic cabling carries signals, which have been converted from electrical to optical (pulses of light) form. It consists of the core, either an extremely thin cylinder of glass or optical quality plastic, which is surrounded by a second glass or plastic layer called the cladding. The interface between the core and cladding can trap light signals by a process called Total Internal Reflection (TIR), resulting in the optical fiber acting as a light pipe.

Unshielded Twisted Pair (UTP) Unshielded Twisted Pair (UTP) is a set of three or four pairs of wires with each wire in each pair twisted around the other to prevent electromagnetic interference. UTP cabling uses RJ-45, RJ-11, RS232, and RS-449 connectors. Because it is less expensive and easier to install, UTP is more popular than Shielded Twisted Pair (STP) or Coaxial Cabling.

Shielded Twisted Pair (STP) Shielded Twisted Pair (TP), like UTP, also has four pairs of wires with each wire in each pair twisted together. However, the difference is that STP is surrounded with a foil shield and copper braided around the wires that allows more protection from any external electromagnetic interference. TYPES OF UTP cable

1. Straight CableUsually use straight cable to connect different type of devices.1) Connect a computer to a switch/hub's normal port.2) Connect a computer to a cable/DSL modem's LAN port.

2. Crossover Cable

It is usually used to connect same type of devices. 1) Connect two computers directly.2) Connect a router's LAN port to a switch/hub's normal port.

Rollover cable A rollover cable is a network cable that connects a computer terminal to network routers console port.

IP Addresses

IP" stands for Internet Protocol, so an IP address is an Internet Protocol address. It is a fascinating product of modern computer technology designed to allow one computer (or other digital device) to communicate with another via the Internet.There are broadly two types of IPsInternet Protocol version 6(IPv6) is the most recent version of theInternet Protocol(IP), thecommunications protocolthat provides an identification and location system for computers on networks and routes traffic across theInternet. Internet Protocol version 4(IPv4) is the fourth version of theInternet Protocol.

TYPES OF IP ADDRESSESPublic IP AddressA public IP address is assigned toevery computer that connects to the Internet where eachIPis unique.In this case, there cannot exist two computers with the same public IP address all over the Internet.

Public IP addressAn IP address is considered private if the IP number falls within one of the IP address ranges reserved for private networks such as a Local Area Network (LAN).

Automatic Private IP Addressing (APIPA) Automatic Private IP Addressing (APIPA) is a feature ofWindows-basedoperating systems that enables a computer to automatically assign itself anIP addresswhen there is no Dynamic Host Configuration Protocol (DHCP) server available to perform that function. APIPA serves as a DHCP serverfailovermechanism and makes it easier to configure and support small local area networks (LANs). The computer selects anIP addressfrom a range of addresses from 169.254.0.0 - 169.254.255.255) reserved by the Internet Assigned Numbers Authority (IANA)

Cisco Certified Network Associate[CCNA] is a popular industry certification program in computer networking developed byCisco Systems. The CCNA program began in 1998 with one core certification focused on network Routing and Switching, obtainable by passing a single 75-minute written exam.In 2013, Cisco began expanding the program to cover many other facets of computer networking and network administrationCCNA(Routing & Switching)Some of the modules under the CCNA course comprise of basic router configuration, IP routing, NAT/PAT, virtual LAN, catalyst switch operation, IP traffic management with ACL, etc.Those who specialize in the various courses offered by CCNA have better job opportunities.

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CISCO Certification

Software used: CISCO Packet TracerPacket Traceris across-platformvisualsimulationprogram designed byCisco Systemsthat allows users to createnetwork topologiesand imitate moderncomputer networks.

Packet Tracer allows users to create simulated network topologies by dragging and dropping routers, switches and various other types of network devices. A physical connection between devices is represented by a "cable" item .

Packet Tracer supports an array of simulatedApplication Layer protocols, as well as basic routing withRIP,OSPF,EIGRP,BDP, to the extents required by the currentCCNAcurriculum.

Packet Tracer is a cross-platform network simulator designed by Cisco Systems to run on Mac OS, Linux and Microsoft Windows.

Arouteris anetworking devicethat forwardsdata packetsbetweencomputer networks.ROUTERS and its Types Broadband RoutersBroadband routers can do different types of things. Broadband routers can be used to connectcomputersor to connect to the Internet.Wired & Wireless RoutersWired router has physical connection whereas wireless routers create a wireless signal home or office. So, anyPCwithin range of Wireless routers can connect it and use your Internet.Edge RouterThis type of router are placed at the edge of the ISP network, they are normally configured to externalprotocollike BGP (Border gateway protocol) to another BGP of other ISP or large organization.Inter-provider Border RouterThis type of router isfor Interconnecting ISPs, this is a BGP speaking router that maintains BGP sessions with other BGP speaking routers in other providers' Assess.

TYPES

Fig. Router

ROUTER COMMANDS

i) Basic Router Commands

ii) ROUTING COMMANDS : To Show

Cisco router copy commands

PASSWORD COMMANDS FOR ROUTERS

(i) Console PortCisco devices allow password protection of console access. This tech-recipe describes configuring the use of a password to protect the console of a Cisco switch.Router(config)#line console 0Router(config)#password CCNARouter(config)#loginRouter(config)#exit

(ii) Auxiliary portRouter(config)#line aux 0Router(config)#password CCNARouter(config)#loginRouter(config)#exit(iii) Enable passwordRouter(config)#enable password CCNARouter(config)#exitRouter(config)#service password-encryption

To assign IP ADDRESS to Routers

Router 1 Router(config)#interface serial 0/0/0Router(config)#ip address 11.0.0.1 255.0.0.0Router(config-if)#no shutdownRouter(config-if)#exitRouter(config)#interface fast ethernet 0/0Router(config)#ip address 10.0.0.1 255.0.0.0Router(config-if)#no shutdownRouter(config-if)#exitRouter 2Router(config)#interface serial 0/0/0Router(config)#ip address 11.0.0.2 255.0.0.0Router(config-if)#no shutdownRouter(config-if)#exitRouter(config)#interface fast ethernet 0/0Router(config)#ip address 20.0.0.1 255.0.0.0Router(config-if)#no shutdownRouter(config-if)#exit

ROUTINGRouting is the process of moving apacketof data from sourcetodestination. Routing is usually performed by a dedicated device called arouter.

PING: Ping is a network diagnostic tool used primarily to test the connectivity between two nodes or devices. To ping a destination node, an Internet Control Message Protocol (ICMP) echo request packet is sent to that node.

1. Static routingStatic routingis a form ofroutingthat occurs when a router uses a manually-configured routing entry, rather than information from a dynamic routing traffic.In many cases, static routes are manually configured by anetwork administratorby adding in entries into arouting table.

2. Default RoutingDefault routeis a setting on a computer that defines thepacketforwarding rule to use when no specific route can be determined for a givenInternet Protocol(IP) destination address.

Router(config)#ip route 0.0.0.0 0.0.0.0 11.0.0.2Router(config)#ip route 0.0.0.0 0.0.0.0 12.0.0.2Route(config)#ip route 0.0.0.0 0.0.0.0 12.0.0.1Route(config)#ip route 0.0.0.0 0.0.0.0 13.0.0.1Route(config) #ip route 0.0.0.0 0.0.0.0 14.0.0.2

Router(config)# IP route network ID subnet mask Next IP address

3. Dynamic RoutingDynamic routing, also calledadaptive routing, describes the capability of a system, through which routes are characterized by their destination, to alter the path that the route takes through the system in response to a change in conditions.There are three types of Routing Protocols:Distance vectorLinc state Hybrid

Router metrics: Metric is a measure used to decide which route is better (lower number is better). Each routing protocol uses its own metric. For example, RIP uses hop counts as a metric, while OSPF uses cost.

1. Distance-vector Routing Protocols: Distance-vector Routing Protocolsuse simple algorithms that calculate a cumulative distance value between routers based on hop count.

.

RIP (Routing Info. Protocol)IGRP(Interior Gateway Routing Protocol)

Administrative DistanceAdministrative distance number is used by routers to find out which route is better (lower number is better).

RIP(Routing Information ProtocolRouter(config)# Router RIPRouter(config)#Version 2Network 11.0.0.0Network 10.0.0.0Routing Information Protocol Version 2 (RIPv2)

Distance-Vector protocolwhich some characteristics ofLink State routing protocols. RIPv2 is classless routing, which allows us to use subnetted networks also RIPv2 has the option for sending network mask in the update to allow classless routing. RIPv2 supportVLSM (Variable Length Subnet Masking). RIPv2 support maximummetric(hop count) value of 15. Any router farther than 15 hops away is considered as unreachable. RIPv2 supports triggered updates.2. Link-state Routing Protocols:Link-state Routing Protocolsuse sophisticated algorithms that maintain a complex database of internetwork topology.

OSPF

OSPF(Open Shortest Path First)OSPF officially was documented in 1989 by the Internet Engineering Task Force (IETF) to address many of the limitations of distance vector protocols, such as RIP and IGRP. OSPF become the standardopenrouting protocol. The wordopenis used because the algorithm that drives OSPF, Dijkstra's Shortest Path First (SPF) algorithm, isn't proprietary to any vendor or organization. This allows for mainframes such as IBM, Unisys, and DEC, as well as other manufacturers' routers, to run OSPF.FEATURESFast convergenceSupport for VLSM, super netting, and summarizationSupport for large network diameters. Stub area routingLarge networks are supported because stub-area routing reduces the routing table. Fully classless routing protocol

Commands

Router 1Router(config)#router OSPF 100Router(config)#Network 10.0.0.0 0.255.255.255 area 0Router(config)#Network 192.168.1.0 0.0.0.255 area 0Router 2Router(config)#router OSPF 100Router(config)#Network 10.0.0.0 0.255.255.255 area 0Router(config)#Network 11.0.0.0 0.255.255.255 area 1Router(config)#Network 192.168.2.0 0.0.0.255 area 0Router 3Router(config)#router OSPF 100Router(config)#Network 11.0.0.0 0.255.255.255 area 0Router(config)#Network 192.168.3.0 0.0.0.255 area 1

3. Hybrid Routing Protocols:Hybrid Routing Protocolsuse a combination of distance-vector and link-state methods that tries to incorporate the advantages of both and minimize their disadvantages.

EIGRPEnhanced Interior Gateway Routing Protocol (EIGRP)is an advanceddistance-vector routing protocolthat is used on acomputer networkfor automatingroutingdecisions and configuration.Maximum hop count =224Administrator distance=90Supports subnet+VLSM

Commands Router(config)#Router EIGRP 500Router(config)#network 11.0.0.0Router(config)#No auto-summary

EIGRP

ACLAccess control lists (ACLs) provide a means to filter packets by allowing a user to permit or deny IP packets from crossing specified interfaces.

(i) Extended ACL (Destination based)Extended Access Control Lists (ACLs) allow you to permit or deny traffic from specific IP addresses to a specific destination IP address and port. It also allows you to specify different types of traffic such as ICMP, TCP, UDP, etc. Needless to say, it is very granular and allows you to be very specific.CommandsRouter (config)#access-list 100 deny tcp host ip 20.0.0.2 host 10.0.0.3 EQ 80Router(config)#access-list 100 permit tcp any host 10.0.0.3 EQ 80Router(config)#access-list 100 permit IP any anyRouter(config)#interface fast Ethernet 0/0Router(config)#ip access-group100 in(ii) Standard ACL (Number based)

CommandsRouter(config)#access-list N deny 20.0.0.2Router(config)#access-list N permit anyRouter(config)#interface Se0/0/0Router(config)#ip access-group N in

(iii) Standard ACL (Name based)Router(config)#IP access-list standard abcRouter(config)#deny 20.0.0.2Router(config)#permit anyRouter(config)#exitRouter(config)#interface Se0/0/0Router(config)#ip access-group abc in

Switching is process to forward packets coming in from one port to a port leading towards the destination.

SWITCHING

VLANA local area network, orLAN, provides the nodes connected to it with direct (Layer 2) access to one another

Commands to create VLANSwitch(config)#VLAN 2Switch (config)#name Sales

To assign Ports in VLANSwitch(config)#interface fastethernet0/1Switch (config) #switch port mode accessSwitch (config) #switch port access VLAN 2

VTP (Virtual Trunking Port)VTP) is a protocol created by Cisco to create and manage VLANs for a large network with many interconnected switches and to maintain consistency throughout the network. A network switch, which is participating inVLAN Trunking Protocol (VTP), can have three different modes.Server ModeClient ModeTransparent Mode

PORT SECURITY

Method-ISwitch(config)#interface fastethernet 0/11Switch(config)#switchport mode accessSwitch(config)#switchport port security mac 21.13.8.1Remove pc and again connect to give the following commandSwitch(config)#interface fast Ethernet 0/11Switch(config)#shutdownSwitch(config)#no shutdown

Method IISwitch(config)#interface fast Ethernet 0/11 Switch(config)#Switch port port-securitySwitch(config)#switch port port-security mac-address stickySwitch(config)#switch port port-security max-2Switch(config)#switch port port-security violation shutdown

NATNetwork Address Translation(NAT) is the process where a network device, usually a firewall, assigns a public address to a computer (or group of computers) inside a private network. The main use of NAT is to limit the number of public IP addresses an organization or company must use, for both economy and security purposes. The most common form of network translation involves a large private network using addresses .Types of NAT1.Static NAT (Network Address Translation) Static NAT (Network Address Translation) is one-to-one mapping of a private IP addressto a public IP address.COMMANDSSwitch(config)#IP NAT inside source static 10.0.0.2 122.122.100.10Switch(config)#IP nat inside source static 10.0.0.3 122.122.100.11Switch(config)#interface fastethernet 0/0Switch(config)#IP nat inside exitSwitch(config)#interface serial 0/0/0Switch(config)#IP nat outside

2.Dynamic NAT (Network Address Translation) Dynamic NAT can be defined as mapping of aprivate IP addressto a public IP address from a group of public IP address.COMMANDSSwitch(config)#interface fast Ethernet 0/0Switch(config)#IP Nat insideSwitch(config)#exitSwitch(config)#interface serial 0/0/0Switch(config)#IP nat outsideSwitch(config)#exitSwitch(config)#access-list 10 permit 10.0.0.0 0.255.255.255.255Switch(config)#IP nat pool abc 122.122.200.10 122.122.200.10 netmask 255.255.255.0Switch(config)#IP Nat inside source list 10 pool abc

3. PAT (Port Address Translation)Port Address Translation (PAT) is another type of dynamic NAT which can map multipleprivate IP addressesto a single public IP address by using a technology known as Port Address Translation.

CommandsSwitch(config)#access-list 10 permit 10.0.0.0 0.255.255.255Switch(config)#IP nat pool abc 122.122.200.20 122.122.200.20 net mask 255.255.255.0Switch(config)#IP nat inside source list 10 pool abc overloadsSwitch(config)#interface fast Ethernet 0/0Switch(config)IP Nat insideSwitch(config)#exitSwitch(config)#interface serial 0/0/0Switch (config)#IP Nat outside

Subnetting is a process of dividing large network into the smaller networks based on layer 3 IP address. Every computer on network has an IP address that represent its location on network. Two version of IP addresses are available IPv4 and IPv6.

Class A addresses range from 1-126Class B addresses range from 128-191Class C addresses range from 192-223Class D addresses range from 224-239Class E addresses range from 240-254Subnet maskSubnet mask is a 32 bits long address used to distinguish between network address and host address in IP address. Subnet mask is always used with IP address. Subnet mask has only one purpose, to identify which part of an IP address is network address and which part is host address.

SUBNETTING

Class Subnet Mask Format A255.0.0.0Network.Host.Host.Host B255.255.0.0Network.Network.Host.Host C255.255.255.0Network.Network.Network.Host

Acomputer networkordata networkis atelecommunications networkwhich allowscomputerstoexchange data. In computer networks, networked computing devices exchange data with each other using adata link. The connections between nodes are established using eithercable mediaorwireless media. The best-known computer network is theInternet. Computer networks support an enormous number ofapplicationsandservicessuch as access to theWorld Wide Web,digital video,digital audio, shared use ofapplication and storage servers,printers, andfax machines, and use ofemailandinstant messagingapplications as well as many others. In most cases, application-specific communications protocols arelayered(i.e. carried aspayload) over other more general communications protocols.

CONCLUSION

Textbooks:[1] Goleniewski, L. (2006)Telecommunications Essentials, Addison Wesley Professional.)[2 ]Kurose, J.F. and K.W. Ross (2003)Computer Networking: A Top Down Approach Featuring the Internet, Addison Wesley.)[3] Mir, N.F. (2006)Computer and Communication Networks, Prentice Hall.[4]Computer Networks by Andrew S. Tanenbaum[5] Internetworking with TCP/IP, Volume 1 by Douglas Comer. [6] Sam Halabi & Danny McPherson,Internet Routing Architectures. [7 ]Christian Huitema,Routing in the Internet.Research Papers:[8][3ComWHITE] 3Com, "Understanding IP Addressing: Everything You Ever wanted to Know," White Paper, May 2001. [9][Cisco IP] Cisco, "Internet Protocols," Internetworking Technology Handbook.[10][Cisco Routing] Cisco, "Routing Basics," Internetworking Technology Handbook.

REFERENCES