Network +Introduction to NetworkingWhat is a network :The word “ network “ means, “ two computers are connected using atransmission media and are able to share their resources, transfer data.The transmission media for the term network is either cable media orwireless media.Advantage of Networking :1. Resource sharing : buy devices for all computers in same network, notone device for one computer.2. High reliability : all files can be copied to two or more machines, if onegoes down, we can use other.3. Communication media : using the media. Two or more devices can beinterconnected to share resources & exchange information.4. High speed : information can be synchronized when one user makeschanges to on line document, the other can see the change immediately.
Layer 3 Device. Works at the Network LayerForwards Data packets based on IP AddressThis allows Routers to choose the best path thru the NetworkImportant Traffic regulating device on large NetworksCan have inbuilt security features-Firewall,Authentication.
1. A router is a device which is used in our network toconnect two different networks.2. Routers, by default, will not forward any broadcasts.3. Routers use the logical address in a network layer todetermine the next hop router or a host which islocated on a remote place.4. Routers can use access lists, created by anadministrator, to control security on the types ofpackets that are not allowed to enter or exit aninterface.
The algorithm used for the routing protocolsdefines the following processes: Mechanism for sending and receiving routinginformation. Mechanism for calculating the best paths and installingroutes in the routing table. Mechanism for detecting and reacting to topologychanges.
Classless (Use of VLSM) or Classful - Classless routingprotocols include the subnet mask in the updates. This feature supports the use of Variable Length Subnet Masking(VLSM) and better route summarization. Classful routing protocols do not include the subnet mask andcannot support VLSM. Time to Convergence - Time to convergence defines howquickly the routers in the network topology sharerouting information and reach a state of consistentknowledge. The faster the convergence, the more preferable the protocol. Scalability - Scalability defines how large a network canbecome based on the routing protocol that is deployed. The larger the network is, the more scalable the routing protocolneeds to be
Resource Usage - Resource usage includes therequirements of a routing protocol such as memoryspace, CPU utilization, and link bandwidthutilization Higher resource requirements necessitate more powerfulhardware to support the routing protocol operation inaddition to the packet forwarding processes. Implementation and Maintenance - Implementationand maintenance describes the level of knowledgethat is required for a network administrator toimplement and maintain the network based on therouting protocol deployed.
Static RoutingThe command syntaxIp route [ destination_network] [ Destination subnet mask ] [<next hop ip address >or <exit interface type><No.> ]This list describes each command in the stringip route : the command used to create the static routing.destination_network : the network you are placing in therouting table.mask : the subnet mask being used on the network.next hop address : the address of the next hop router that willreceive the packet and forward it on the remote network.
A router using a distance vector routingprotocol does not have the knowledge of theentire path to a destination network. The router only knows The direction or interface in which packets should beforwarded and The distance or how far it is to the destinationnetwork
Some distance vector routing protocols call forthe router to periodically broadcast the entirerouting table to each of its neighbors. This method is inefficient because the updatesnot only consume bandwidth but also consumerouter CPU resources to process the updates.
161. Each router establishes a relationship (“adjacency”)with its neighbors2.Each router generates link state advertisements (LSAs)which are distributed to all routersLSA = (link id, state of the link, cost, neighbors of the link)3. Each router maintains a database of all receivedLSAs (topological database or link state database), whichdescribes the network has a graph with weightededges4. Each router uses its link state database to run ashortest path algorithm (Dijikstra’s algorithm) toproduce the shortest path to each network
17 With distance vector routing, each node hasinformation only about the next hop: Node A: to reach F go to B Node B: to reach F go to D Node D: to reach F go to E Node E: go directly to F Distance vector routing makespoor routing decisions ifdirections are not completelycorrect(e.g., because a node is down). If parts of the directions incorrect, the routing may be incorrect until therouting algorithms has re-converged.A B CD E F
18 In link state routing, each node has a complete mapof the topology If a node fails, eachnode can calculatethe new route Difficulty: All nodes need tohave a consistent view of thenetworkA B CD E FA B CD E FA B CD E FA B CD E FA B CD E FA B CD E FA B CD E F
Enhanced IGRP is a distance vector routing protocol. Why it is called enhanced IGRP.Because like IGRP, EIGRP uses the concept of an autonomous system to describe theset of contiguous routers that run the same routing protocol and share routinginformation. But unlike IGRP, EIGRP includes the subnet mask in its route updates.EIGRP is some times referred to as a Hybrid routing protocol. EIGRP has a maximumhop count of 255.There are no. of powerful features for EIGRP, the main ones are listed here :It uses max hop count of 255It is a classless routing protocolIt is sometimes referred to as a hybrid routing protocolLike IGRP, EIGRP uses AS ( autonomous system number ) to share it’s routing table.EIGRP uses RTP ( Reliable Transport Protocol ) for communicationIt uses Dual ( Diffusing update algorithm ) for the selection of best pathSupports all layer 3 protocols(IPv4,IPX and IPv6)Supports VLSM/CIDR
Configuring OSPF :These two elements are the basic elements of OSPF configuration :Enabling OSPFConfiguring OSPF areasEnabling OSPFRouter( config )# router ospf ?<1-65535>A value in the range 1-65535 identifies the ospf process ID. It’s a unique no.on this router that groups a series of ospf configuration commands under aspecific process. Different ospf routers don’t have to use the same process IDin order to communicate.Configuring OSPF areasRouter# config tRouter( config t )# router ospf 1Router( config – router )# network 10.0.0.0 0.255.255.255 area 0
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