Solution _Assignment #2 for Computer Networks This assignment covers material from Unit 1, 2 and 3 1. OSI Layer working 2. Difference between TCP/IP and OSI (At least 6 points) 3. Details of all Protocols form all layers. 4. Working of each Networking devices 5. Working of networking commands with Syntax 6. Difference between a. TCP, UDP and SCTP, b. HTTP & SMTP c. HTTP &FTP d. HTTP 1.0 & HTTP1.1 e. Persistant &Non-Persistant f. FTP & TFTP g. IMAP &POP3 h. SMTP & FTP i. Connectionless & Connection-Oriented j. IPV4 & IPV6 k. Distance Vector & Link State Routing l. RIP & OSPF m. Classful & Classless(CIDR) Addressing n. Switch & Hub o. Switch & Bridge p. Switch & Router 7. Header Formats and diagram of following a. HTTP request & response b. FTP c. SMTP d. MIME e. DHCP f. TELNET g. DNS h. TCP i. UDP & Pseudo UDP j. SCTP k. RTP l. TCP in wireless network m. RSVP n. Differentiated Services o. IPV4 p. IPV6 q. ARP & RARP r. RIP s. IP t. OSPF u. BGP 8. Prepare table for following: 1> IPV4 Classful addressing 2> IPV4 Private Address 9. Examples of all subnetting for Classful and Classless(CIDR) addressing
1. OSI Layer working OSI Layer Name Application Presentatio n Session Transport Network Data Link Physical Working of That Layer The application layer is responsible for providing services to the user. Resource sharing Provides a set of interfaces for sending and receiving applications to gain access to and use network services This layer is also responsible for certain protocol conversions, data encryption/decryption, or data compression/decompression. Manages data format, it converts data into a generic format Responsible for initiating, maintaining and terminating sessions Responsible for security and access control to session information (via session participant identification) Responsible for synchronization services, and for checkpoint services Manages the flow of data between parties by segmenting long data streams into smaller data chunks Reliable transmission (Provides Acks of successful transmissions and requests resends for packets which arrive with errors) Provides Congestion control and flow control Multiplexing and demultiplexing End-to-end data delivery Responsible for deciding how to route transmissions between computers Find best route to route the packet This layer also handles packet switching and network congestion control Handles special data frames (packets) between the Network layer and the Physical layer Error control, Flow control,framing Converts bits into electronic signals & Viceversa This layer manages the interface between the computer and the network medium Protocols work on that Layer HTTP, HTTPS, SMTP, MIME, PoP3,IMAP,FTP, TFTP, DHCP, DNS, Telnet TCP,UDP,SCTP,R TP IPV4,IPV6,IPSec, ARP,RARP,ICMP, OSPF,BGP,RIP,IG MP SLIP,PPP, Sliding window, Go back-n, Selective repeat N/W Devices work on that layer Application Gateway Transport Gateway Router Switch, Bridge Hub, Repeater
2. Difference between TCP/IP and OSI (At least 6 points) Basis for TCP/IP Model OSI Model Comparison Expands To TCP/IP- Transmission Control Protocol/ OSI- Open system Interconnect Internet Protocol Meaning It is a client server model used for transmission of data over the internet. It is a theoretical model which is used for computing system. No. Of Layers 4 Layers 7 Layers Developed by Department of Defense (DoD) ISO (International Standard Organization) Tangible Yes No Usage Mostly used Never used 3. Details of all Protocols form all layers. Protocol Name HTTP SMTP POP3 IMAP FTP TFTP Long form Port No Working Using TCP or UDP Hypertext 80 Used to browse Web Pages TCP Transfer Protocol Simple Mail 25 Internet standard for electronic mail TCP Transfer Protocol (email) transmission Post Office version 110 e-mail is received and held for you by TCP 3 Internet Message Access Protocol File Transfer Protocol Trivial File Transfer Protocol your Internet server. 143 stores email messages on a mail server, but allows the end user to view and manipulate the messages as though they were stored locally on the end user's computing device(s). 20,21 used for the transfer of computer files from a server to a client using the Client server model 69 transferring files that is simpler to use than the File Transfer Protocol (FTP) but less capable. It is used where user TCP TCP UDP and TCP
authentication and directory visibility are not required. DHCP Dynamic Host Configuration Protocol (DHCP) 67,68 Automatically provides an IP address and other related configuration information such as the subnet mask and default gateway. DNS Domain Name 53 an Internet service that translates System domain names into IP addresses and vice versa Telnet Telnet 23 Using Telnet Client and Server, you can create a remote command console session on a host. You can run command line programs, shell commands, and scripts in a remote command console session just as though you were locally logged on to the host and using a local command prompt window. TCP UDP SCTP RTP IPV4 IPV6 ICMP ARP Transmission Control Protocol User Datagram Protocol Stream Control Transmission Protocol (SCTP) Real time Transport Protocol Internet Protocol Version 4 (IPv4) Internet Protocol Version 6 (IPv6) The Internet Control Message Protocol (ICMP) The address resolution 17 Defines how to establish and maintain a network conversation via which application programs can exchange data. TCP works with the Internet Protocol (IP), which defines how computers send packets of data to each other. 6 Alternative communications protocol to Transmission Control Protocol (TCP) used primarily for establishing low-latency and loss tolerating connections between applications on the Internet. 132 SCTP (Stream Control Transmission Protocol) is a protocol for transmitting multiple streams of data at the same time between two end points that have established a connection in a network. Delivering audio and video over IP networks. It is the fourth revision of the IP and a widely used protocol in data communication over different kinds of networks Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. It is used by network devices, like routers, to send error messages and operational information indicating, for example, that a requested service is not available or that a host or router could not be reached. Used to map IP network addresses to the hardware addresses (Logical to Physical) UDP TCP and UDP TCP UDP
RARP RIP OSPF BGP SLIP PPP protocol (arp) Reverse address resolution protocol (rarp) The Routing Information Protocol (RIP) Open Shortest Path First (OSPF) Border Gateway Protocol (BGP) Serial Line Internet Protocol. Point-to-Point Protocol Used to map hardware addresses to IP network addresses (Physical to Logical) one of the oldest distance-vector routing protocols which employ the hop count as a routing metric. RIP prevents routing loops by implementing limit on the number of hops allowed in a path from source to destination. A routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous system (AS). A standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. The protocol is often classified as a path vector protocol but is sometimes also classed as a distancevector routing protocol. SLIP is the result of the integration of modem protocols prior to the suite of TCP/IP protocols. It is a simple Internet link protocol. In computer networking, Point-to-Point Protocol (PPP) is a data link (layer 2) protocol used to establish a direct connection between two nodes. 4. Working of each Networking devices Network Devices Modems ISDN Network Interface Cards (NICs) Gateways Brouters Working Modem is a device which converts the computer-generated digital signals of a computer into analog signals to enable their travelling via phone lines. The modulator-demodulator or modem can be used as a dial up for LAN or to connect to an ISP. ISDN (Integrated Services Digital Network) are used to send over graphic or audio data files. It is a WAN technology that can be used in place of a dial up link. Network Interface Cards (NICs) are hardware devices that connect a computer with the network. They are installed on the mother board. They are responsible for developing a physical connection between the network and the computer. Gateway is a device which is used to connect multiple networks and passes packets from one packet to the other network. Acting as the gateway between different networking systems or computer programs, a gateway is a device which forms a link between them Brouters are the combination of both the bridge and routers. They take up the functionality of the both networking devices serving as a bridge when forwarding data between networks, and serving as a router when routing data to individual systems. Brouter functions as a filter that allows some data into the local network and redirects unknown data to the other network.
Routers Routers are network layer devices and are particularly identified as Layer- 3 devices of the OSI Model. They process logical addressing information in the Network header of a packet such as IP Addresses. Bridges Switches Hub Functionality: To connect different network segments. To connect different network protocols such as IP and IPX. To connect several smaller networks into a large network (known as internetwork) To break a large network in smaller networks (Known as subnet usually created to improve the performance or manageability) To connect two different media types such as UTP and fiber optical. To connect two different network architectures such as token ring and Ethernet. To connect LAN network with Telco company s office (Known as DTE device). To access DSL services (known as DSL Router). A bridge is a computer networking device that builds the connection with the other bridge networks which use the same protocol. It works at the Data Link layer of the OSI Model and connects the different networks together and develops communication between them. It connects two local-area networks; two physical LANs into larger logical LAN or two segments of the same LAN that use the same protocol. Types of Bridges: 1. Transparent Bridge 2. Source Route Bridge 3. Translational Bridge Switches are connected to them through twisted pair cabling. But the difference shows up in the manner both the devices; hub and a switch treat the data they receive. Hub works by sending the data to all the ports on the device whereas a switch transfers it only to that port which is connected to the destination device. A switch does so by having an in-built learning of the MAC address of the devices connected to it. The following method will explain further how data transmission takes place via switches: Cut-through transmission: It allows the packets to be forwarded as soon as they are received. Store and forward: In this switching environment the entire packet are received and checked before being forwarded ahead. Fragment Free: In a fragment free switching environment, a greater part of the packet is examined so that the switch can determine whether the packet has been caught up in a collision. Hubs are fundamentally used in networks that use twisted pair cabling to connect devices. They are designed to transmit the packets to the other appended devices without altering any of the transmitted packets received. Hub falls in two categories: Ethernet Hubs Active Hub: They are smarter than the passive hubs. They not only provide the path for the data signals infact they regenerate, concentrate and strengthen the signals before sending them to their destinations. Active hubs are also termed as repeaters. Passive Hub: They are more like point contact for the wires to built in the physical network. They have nothing to do with modifying the signals. It is a device connecting multiple Ethernet devices together and makes them perform the functions as a single unit. They vary in speed in terms of data
Repeater transfer rate. Ether utilizes Carrier Sense Multiple Access with Collision Detect (CSMA/CD) to control Media access. Ethernet hub communicates in half-duplex mode where the chances of data collision are inevitable at most of the times A repeater operates at the physical layer. Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network. An important point to be noted about repeaters is that they do no amplify the signal. 5. Working of at least 10 networking commands Networking Commands netstat tcpdump ping hostname traceroute ifconfig NSLOOKUP Command ROUTE Command HOST Command ARP Command HOSTNAME Command Working/Use Displays contents of /proc/net files. It works with the Linux Network Subsystem, it will tell you what the status of ports are ie. open, closed, waiting, masquerade connections. It will also display various other things. It has many different options This is a sniffer, a program that captures packets off a network interface and interprets them for you. It understands all basic internet protocols, and can be used to save entire packets for later inspection. The ping command (named after the sound of an active sonar system) sends echo requests to the host you specify on the command line, and lists the responses received their round trip time. Tells the user the host name of the computer they are logged into traceroute will show the route of a packet. It attempts to list the series of hosts through which your packets travel on their way to a given destination. Also have a look at xtraceroute (one of several graphical equivalents of this program). This command is used to configure network interfaces, or to display their current configuration. In addition to activating and deactivating interfaces with the up and down settings, this command is necessary for setting an interface's address information if you don't have the ifcfg script. nslookup command also use to find out DNS related query. The following examples shows A Record (IP Address) of tecmint.com. route command also shows and manipulate ip routing table. To see default routing table in Linux, type the following command. host command to find name to IP or IP to name in IPv4 or IPv6 and also query DNS records. ARP (Address Resolution Protocol) is useful to view / add the contents of the kernel s ARP tables. To see default table use the command as. hostname is to identify in a network. Execute hostname command to see the hostname of your box. netstat Syntax tcpdump ping ip_or_ host_name traceroute machine_nam e_ or_ip ifconfig NSLOOKUP hostname route HOST hostname arp -e HOSTNAME
6. Differentiate between following (at least 4 points for each difference) i. TCP, UDP and SCTP UDP TCP SCTP Message oriented protocol Byte oriented protocol Message oriented protocol Preserve message boundaries Does not Preserve message Preserve message boundaries boundaries Unreliable Reliable Reliable No congestion and flow control Have congestion and flow control Have congestion and flow control Each message follows different route so no sequencing Each message follows same route so have in sequence data delivery Port no 17 Port no 6 Port no 132 have in sequence data delivery ii. HTTP & SMTP SMTP HTTP Transfer files (eg;email messages) from one m Transfers files from web server to web user age server to another mail server (ie. The browser) Push protocol: the sending mail server pushes t Pull protocol: someone loads information on a w file to the receiving mail server. In particular, t server and users use HTTP to pull the informati TCP connection is initiated by the machine th offthe server at their convenience. In particular, t wants to send the file. TCP connection is initiated by the machine th wants to receive the file. Requires each user message, including the body Do not impose this restriction each message to be in 7 bit ASCII format. If t message contains that are not 7-bit ASCII, then t message has to be encoded into 7-bit ASCII Uses TCP Protocol Uses TCP Protocol Port no is 25 Port no is 80 multiple objects sent in multipart message each object encapsulated in its own respon message iii. HTTP &FTP HTTP HTTP uses TCP Only one TCP connection between client and server Send its control information in-band HTTP is stateless FTP FTP uses TCP Two parallel TCP connection, one for data and one for control Send its control information out-of-order FTP maintains State
iv. Persistent & Non-Persistent (HTTP 1.0/1.1) Persistent Uses HTTP/1.0 Have only 16 status codes Provides only basic authentication Uses Non persistent connection RTT is more so bandwidth waste is vast Stateless Supports only GET POST and HEAD method Non-Persistent Uses HTTP/1.1 Have introduced new 24 status code Provides strong authentication Uses Persistent connection RTT is less so bandwidth utilization is good Uses cookies as state management mechanism Supports GET, POST, HEAD,PUT and DELETE v. FTP & TFTP Basis for FTP TFTP Comparison Abbreviation File Transfer Protocol. Trivial File Transfer Protocol. Authentication Authentication is required in FTP for No authentication is required in TFTP. communication between client and server. Service FTP uses TCP service which is a connection-oriented service. TFTP uses UDP service which is connection-less service. Software FTP software is larger than TFTP. TFTP software is smaller than FTP and fits into readonly memory of the diskless workstation. Connection FTP establishes two connections one for data(tcp port no. 21) and one for TFTP establishes a single connection for its file transfer (UDP port no. 69). control(tcp port no. 20). Commands/M FTP have many commands. TFTP have only five messages. essage Complexity FTP is more complex TFTP is less complex. vi. IMAP &POP3
vii. SMTP & FTP Feature FTP SMTP TCP port 20 and 21 25 number RFC reference RFC959 RFC821, RFC822 and RFC974 documents Protocol function Used to transfer files from remote computer after connection is established Used to e-mail send messages between computers. This is done either using SMTP server or using mail function. viii. Connectionless & Connection-Oriented Connection oriented Connectionless 1> Connection Establishment use it and Release it. 1>No connection establishment 2> Reliable 2>Not Reliable 3>Information can be resent to receiver if data is missed or with error 4>Packets come in sequence 5>Each packet uses same route 6>If connection fails cannot sent data 3>It is not Possible 4>No sequencing 5>Different route 6>Can sent data using diff route ix. IPV4 & IPV6 Feature IPv4 IPv6 Address 32 bits 128 bits Address Format Dotted Decimal Hexadecimal Notation No of Address 2^32 2^128 IPSec Optional required Payload ID for QoS in the No identification Using Flow label field header Fragmentation Both router and the sending hosts Only supported at the sending hosts Header checksum included Not included Resolve IP address to a link layer address broadcast ARP request Multicast Neighbor Solicitation message
x. Distance Vector & Link State Routing (RIP & OSPF) Distance Vector Routing (RIP) Used in small networks It has a limited number of hops (only 16) High convergence time Periodically advertise updates It has loop problem Updates are broadcasted Advertises only the directly connected routers and full routing tables, Eg. RIP,IGRP, BGP. Link State Routing (OSPF) Used in larger networks It has unlimited number of hops Convergence time is low. Only new changes in a network. No loop problem Updates are multicasted Advertise the updates, and flood the advertisement. Eg. : OSPF, IS-IS xi. Classful & Classless(CIDR) Addressing Classful Addressing Classful addressing divides an IP address into the Network and Host portions along octet boundaries; this portion is fixed for each class. In the classful addressing system all the IP addresses that are available are divided into the five classes A,B,C,D and E. Each of the IP address belongs to a particular class that's why they are classful addresses Address of 192.168.0.0 indicates it is Class C address and 24 bits are from N/W side and 8 bits are from Client side. Classless(CIDR) Addressing Classless addressing uses a variable number of bits for the network and host portions of the address. In the classless addressing IP addresses are not divided into classes. Classless addressing treats the IP address as a 32 bit stream of ones and zeroes, where the boundary between network and host portions can fall anywhere between bit 0 and bit 31. CIDR address of 192.168.0.0/29 defines a 29bits are from network side and remaining 3 bits are from client side xii. Switch & Hub Basis for Comparison Hub Switch Layer Physical layer. Layer 1 devices Data Link Layer. Layer 2 Function To connect a network of personal computers together, they can be joined through a central hub. security also can apply Allow to connect multiple device and port can be manage, Vlan can create Data Transmission form Electrical signal or bits Frame (L2 Switch) Frame & Packet (L3 switch) Ports 4/12 ports Switch is multi port Bridge. 24/48 ports Device Type Passive Device (Without Software) Active Device (With Software) & Networking device Used in (LAN, MAN, WAN) LAN LAN Transmission Mode Half duplex Half/Full duplex Broadcast Domain Hub has one Broadcast Domain. Switch has one broadcast domain Definition An electronic device that connects many network device together so that devices can exchange data A network switch is a computer networking device that is used to connect many devices together on a computer network. A switch is considered more advanced than a hub because a switch will on send msg to
device that needs or request it Speed 10Mbps 10/100 Mbps, 1 Gbps Collisions Collisions occur commonly in setups using hubs. No collisions occur in a full-duplex switch. Address used for data tramsmission Uses MAC address Uses MAC address xiii. Switch & Bridge Switch A switch when compared to bridge has multiple ports. Switches can perform error checking before forwarding data. Switches are very efficient by not forwarding packets that error-ed out or forwarding good packets selectively to correct devices only. Switches can support both layer 2 (based on MAC Address) and layer 3 (Based on IP address) depending on the type of switch. Usually large networks use switches instead of hubs to connect computers within the same subnet. Bridge A bridge is more complex than hub. A bridge maintains a MAC address table for both LAN segments it is connected to. Bridge has a single incoming and outgoing port. Bridge filters traffic on the LAN by looking at the MAC address. Bridge looks at the destination of the packet before forwarding unlike a hub.it restricts transmission on other LAN segment if destination is not found. Bridges are used to separate parts of a network that do not need to communicate regularly, but need to be connected. xiv. Bridge & Router
xv. Switch & Router Basis for Comparison Function Router Directs data in a network. Passes data between home computers, and between computers and the modem. Switch Allow to connect multiple device and port can be manage, Vlan can create security also can apply Layer Network Layer (Layer 3 devices) Data Link Layer. Layer 2 of the OSI model. Data Transmission Packet Frame Transmission Type At Initial Level Broadcast then Uni-cast & Multicast First broadcast; then unicast & multicast as needed. Ports 2/4/8 Switch is multi port Bridge. 24/48 ports Used in (LAN, MAN, WAN) LAN, WAN LAN Device Type Networking device Active Device (With Software) & Networking device Table Store IP address in Routing table and maintain address at its own. Switches use content accessible memory CAM table which is typically accessed by ASIC (Application Specific integrated chips). Transmission Mode Full duplex Half/Full duplex Broadcast Domain In Router, every port has its own Broadcast domain. Switch has one broadcast domain [unless VLAN implemented] Definition A router is a networking device that connects a local network to other local networks. At the Distribution Layer of the network, routers direct traffic and perform other functions critical to efficient network operation. A network switch is a computer networking device that is used to connect many devices together on a computer network. A switch is considered more advanced than a hub because a switch will on send msg to device that needs or request it Speed 1-10 Mbps (Wireless); 100 Mbps 10/100 Mbps, 1 Gbps (Wired) Used for Connecting two or more networks Connecting two or more nodes in the same network or different network Address used Uses IP address Uses MAC address Routing Decision Take faster routing decisions Take more time for complicated routing decisions NAT Routers can perform NAT Switches cannot perform NAT 7. Draw Header Formats of following: i. HTTP request Header
HTTP response Header i. FTP ii. SMTP iii. MIME
iv. DHCP Hardware address length (1 byte) Hardware type (2 bytes) Protocol address length (1 byte) Source hardware address* Source protocol address* Target hardware address* Target protocol address* Protocol type (2 bytes) Operation code (2 bytes) * Note: The length of the address fields is determined by the corresponding address length fields v. TELNET vi. DNS Iterative resolution example Recursive resolution example
DNS Header Format vii. TCP Header Format TCP Connection establishment using three-way handshaking
TCP Connection Establishment Scenario (3) Three protocol scenarios for establishing a connection using a three-way handshake. (a) Normal operation, (b) Old CONNECTION REQUEST appearing out of nowhere. (c) Duplicate CONNECTION REQUEST and duplicate ACK. TCP Connection Release- The two-army problem TCP Connection termination using three-way handshaking
TCP Connection Release Scenarios (4) Four protocol scenarios for releasing a connection. (a) Normal case of a three-way handshake. (b) final ACK lost. (c) Response lost. (d) Response lost and subsequent DRs lost. viii. TCP Congestion control
TCP Transmission Policy(Flow control) ix. TCP in wireless network Split TCP: Indirect TCP TCP-aware Link Layers: Snoop
x. UDP Header Pseudo UDP Header xi. SCTP Header xii. RTP Header
xvi. Silly window syndrome Problem The Leaky Bucket Algorithm
The Token Bucket Algorithm xiii. RSVP-The Resource ReSerVation Protocol (a) A network, (b) The multicast spanning tree for host 1. (c) The multicast spanning tree for host 2.
(a) Host 3 requests a channel to host 1. (b) Host 3 then requests a second channel, to host 2. (c) Host 5 requests a channel to host 1. xiv. Differentiated Services Expedited Forwarding Assured Forwarding
xv. IPV4 Header xvi. IPV6 xvii. ARP
xviii. RARP xix. RIP xx. OSPF
xxi. BGP 8. Prepare table for following: 1> IPV4 Classful addressing Name of Class Range Binary Representation No of Network bits No of Host (client)bits Default Mask A 1-127 0 8 24 255.0.0.0 B 128-191 10 16 16 255.255.0.0 C 192-223 110 24 8 255.255.255.0 D 224-239 1110 Used for Multicasting - E 240-255 1111 Reserved for Scientific & Research purpose 2> IPV4 Private Address - Class Address Block A 10.0.0.0 1 B 172.16 TO 172.31 16 C 192.168.0 TO 192.168.255 256 9. Examples of all subnetting for Classful and Classless(CIDR) addressing, taken in classrooms. a) Divide the network 220.125.5.192/26 into 8 sub networks. How many hosts can be connected in each network? Show their IP range, network address and broadcast address. [6] ANS: No of addresses for whole network are N= 2 32-26 =2 6 =64 First Address in network is- 220.125.2.192/26 Last address in network is- 220.125.5.255/26 As 8 subnet has to design so we divide no of address with no of sub networks i.e. 64/8= 8. That means each network has 8 addresses. New subnet mask will be: For 8 network 3 bits are required (log 2 8 =3) to add to /26 mask, so new mask will be 26+3=29.
Sub Network range Network Address Broadcast Address network 1 220.125.5.192/29-220.125.5.199/29 220.125.5.192/29 220.125.5.199/29 2 220.125.5.200/29-220.125.5.207/29 220.125.5.200/29 220.125.5.207/29 3 220.125.5.208/29-220.125.5.215/29 220.125.5.208/29 220.125.5.215/29 4 220.125.5.216/29-220.125.5.223/29 220.125.5.216/29 220.125.5.223/29 5 220.125.5.224/29-220.125.5.231/29 220.125.5.224/29 220.125.5.231/29 6 220.125.5.232/29-220.125.5.239/29 220.125.5.232/29 220.125.5.239/29 7 220.125.5.240/29-220.125.5.247/29 220.125.5.240/29 220.125.5.247/29 8 220.125.5.248/29-220.125.5.255/29 220.125.5.248/29 220.125.5.255/29 b) A company is granted a site address 201.70.64.0. The company needs six subnets. Design the subnets(subnet masks for each subnet, starting and ending address of each subnet. [5] Ans: Step 1) Determine the number of subnets and convert to binary - In this example, the binary representation of 6 = 00000110. Step 2) Reserve required bits in subnet mask and find incremental value - The binary value of 6 subnets tells us that we need at least 3 network bits to satisfy this requirement - Our original subnet mask is 255.255.255.0 (Class C subnet) - The full binary representation of the subnet mask is as follows: 255.255.255.0 = 11111111.11111111.11111111.00000000 - We must convert 3 of the client bits (0) to network bits (1) in order to satisfy the requirements: New Mask = 11111111.11111111.11111111.11100000 -If we convert the mask back to decimal, we now have the subnet mask that will be used on all the new networks 255.255.255.224 New subnet mask 255.255.255.224 If you convert this bit to a decimal number, it becomes the number 32 that is every subnet is having 32 addresses allotted to it (from 0 to 31, then 32 to 63 etc) Step 3) Use increment to find network ranges You can now fill in your end ranges, which is the last possible IP address before you start the next range Subnet No Range Starting Address Ending Address 1 201.70.64.0 201.70.64.31 201.70.64.1 201.70.64.30 2 201.70.64.32 201.70.64.63 201.70.64.33 201.70.64.62 3 201.70.64.64 201.70.64.95 201.70.64.63 201.70.64.94 4 201.70.64.96-201.70.64.127 201.70.64.97 201.70.64.126 5 201.70.64.128-201.70.64.159 201.70.64.129 201.70.64.158 6 201.70.64.160-201.70.64.191 201.70.64.161 201.70.64.190 The first and last address from each range (network / broadcast IP) are unusable C)Suppose a router has build up the routing table shown below. The router can deliver packets directly over interfaces 0 and 1, or it can frward packets to roputers R2,R3 or R4. Describe what the router does with a packet addressed to each of the following destinations. [8] i. 128.96.39.10 ii. 128.96.40.12 iii. 128.96.40.151 iv. 192.4.153.17 v. 192.4.153.90
Routing Table SubnetNumber SubnetMask NextHop 128.96.39.0 255.255.255.128 Interface 0 128.96.39.128 255.255.255.128 Interface 1 128.96.40.0 255.255.255.128 R2 192.4.153.0 255.255.255.192 R3 (Default) R4 Ans: i. 128.96.39.10-Applying the subnet mask 255.255.255.128, we get 128.96.39.0. Use the interface 0 as the next hop. ii. 128.96.40.12-Applying the subnet mask 255.255.255.128, we get 128.96.40.0 (next hop is Router R2) iii. 128.96.40.151- Applying all the subnet mask give 128.96.40.128, None of the subnet number entries match, hence use default Router R4. iv. 192.4.153.17-Applying subnet mask 255.255.255.192, we get 192.4.153.0. Use Router R3 as next hop. v. 192.4.153.90- None of the subnet number entries match, hence use default Router R4 next hop.