5 June - CN - Subnets Part - 1
Duration: 1 hr 58 min
This video lesson is available to enrolled students.
AI Summary
An AI-generated summary of this video lecture.
This lecture provides a comprehensive overview of IP addressing classes, subnetting, and network protocols. The instructor begins by detailing Class C IP addresses, explaining the division between network and host bits, calculating network IDs, and determining first/last hosts and broadcast addresses. The lesson progresses to Class B and introduces the necessity of subnetting to manage large networks efficiently, using a university department scenario as a practical example. Key calculations for subnet masks and host counts are demonstrated. The lecture then covers Class D (multicasting) and Class E (research) addresses. Finally, it delves into the Address Resolution Protocol (ARP), explaining its function in mapping IP addresses to MAC addresses within a local network, and discusses the loopback address for internal system communication.
Chapters
0:00 – 2:00 00:00-02:00
The lecture introduces Class C IP addresses. The instructor writes 'Class-C' on the board and draws a diagram showing four octets. He highlights that the first three octets represent the network part and the last octet is the host part. Key points written include 'Number of network bits are 24' and 'Number of host bits are 8'. The instructor explains that the first three octets are fixed for the network, while the last octet varies for hosts.
2:00 – 5:00 02:00-05:00
The instructor defines the range for Class C addresses as 192 to 223. He writes the subnet mask for Class C as 255.255.255.0. A list of examples is provided on the board, including 192.0.0.0, 192.1.67.69, 203.55.178.231, and others. He notes that 192.0.0.0 is a network address, while others like 192.1.67.69 are host IPs. The instructor emphasizes the structure of Class C addresses for identification.
5:00 – 10:00 05:00-10:00
A specific problem is solved: Given IP 201.55.66.78, find the network address. The instructor identifies it as Class C and applies the mask 255.255.255.0. He performs a bitwise AND operation to determine the Network ID is 201.55.66.0. He explains that the first three octets remain the same as the IP, while the last octet becomes 0 for the network address.
10:00 – 15:00 10:00-15:00
Continuing with the example IP 201.55.66.78, the instructor calculates the first host, last host, and Direct Broadcast Address (DBA). The first host is 201.55.66.1, and the last host is 201.55.66.254. The DBA is 201.55.66.255. He also mentions the Limited Broadcast Address (LBA) as 255.255.255.255. The calculations are derived by setting the host bits to 00000001 for the first host and 11111110 for the last host.
15:00 – 20:00 15:00-20:00
The lecture moves to Class B addresses. An example IP 144.89.93.115 is analyzed. The instructor identifies it as Class B with a mask of 255.255.0.0. He calculates the Network ID as 144.89.0.0. The first host is 144.89.0.1, and the last host is 144.89.255.254. The DBA is 144.89.255.255. This section reinforces the difference in network/host bit allocation between Class B and Class C.
20:00 – 25:00 20:00-25:00
The concept of Subnetting is introduced with the question 'Why do we need Subnetting?'. A diagram shows a large network divided into smaller segments for different departments (CSE, ME, ECE, CE) within MANIT Bhopal. The instructor explains that without subnetting, a single large network would be inefficient. Subnetting allows for better management and security by breaking a large network into smaller, manageable sub-networks.
25:00 – 30:00 25:00-30:00
The instructor discusses a specific subnetting problem: 'Class-C Subnet mask is given as 255.255.255.240. Then find no. of subnets and hosts per subnet.' He explains that the default Class C mask is 255.255.255.0. The new mask 255.255.255.240 borrows bits from the host portion to create subnets. This allows for more networks but fewer hosts per network.
30:00 – 35:00 30:00-35:00
The lecture covers Class D and Class E addresses. Class D is reserved for IPv4 multicasting, with a range of 224 to 239. The instructor notes that Class D addresses cannot be assigned to any system and there is no clear division of network and host parts. Class E is used for research and is reserved for protocol researchers, OS developers, and cybersecurity researchers.
35:00 – 40:00 35:00-40:00
A practical scenario is drawn showing a network with switches, routers, and a gateway. The diagram illustrates how data flows from a local network through a switch to a router (Gateway) and then to the internet or another network. The instructor labels the components, including 'Access Port', 'Interface IP', and 'Gateway'. This visual aid helps explain the physical and logical structure of a network.
40:00 – 45:00 40:00-45:00
The instructor continues with subnetting calculations. He writes '200.197.64.0' and asks to construct 6 subnets. He explains that to get 6 subnets, you need to borrow enough bits from the host portion. Since 2^2 = 4 and 2^3 = 8, borrowing 3 bits is required to get at least 6 subnets. This reduces the number of available hosts per subnet.
45:00 – 50:00 45:00-50:00
The lecture revisits the subnet mask 255.255.255.240. The instructor explains that 240 in binary is 11110000, meaning 4 bits are borrowed for subnetting. This creates 2^4 = 16 subnets. The remaining 4 bits are for hosts, allowing 2^4 - 2 = 14 hosts per subnet. This calculation demonstrates the trade-off between the number of subnets and hosts.
50:00 – 55:00 50:00-55:00
The instructor discusses the Address Resolution Protocol (ARP). He writes 'ARP protocol is used to get MAC of a system when you have its IP but only inside local network'. He explains that ARP stands for Address Resolution Protocol. It is essential for delivering packets within a local network because devices communicate using MAC addresses at the data link layer.
55:00 – 60:00 50:00-55:00
The instructor explains how ARP works. If host A wants to send data to host B in the same network, A needs B's MAC address. A will broadcast an ARP packet in its own network asking 'Who has [IP address]? Reply'. The host with that IP address will reply with its MAC address. This process allows A to build its ARP table.
60:00 – 65:00 55:00-60:00
The lecture covers the ARP table. The instructor explains that devices maintain a table mapping IP addresses to MAC addresses. When a packet needs to be sent, the device checks this table. If the MAC address is not found, an ARP request is broadcast. This table is crucial for efficient communication within a local network.
65:00 – 70:00 60:00-65:00
The instructor discusses the role of the Gateway. He draws a diagram showing a switch connected to a router (Gateway). The Gateway acts as the entry point to another network. He explains that if a device wants to send data to a different network, it sends the packet to the Gateway's MAC address. The Gateway then forwards the packet to the destination network.
70:00 – 75:00 65:00-70:00
The lecture covers the Loopback address. The instructor writes 'Loopback address - Special address used by host to communicate with itself'. He gives the example 127.0.0.0/8. He explains that traffic sent to a loopback address never leaves the system's NIC. It is used for testing and development.
75:00 – 80:00 70:00-75:00
The instructor elaborates on the Loopback address. He writes '127.0.0.1' as the famous and generally used loopback address. He mentions that 127.0.0.0 is the network address and is excluded. The loopback address is used for testing network software without sending packets over the physical network. It is also used by applications to communicate with themselves.
80:00 – 85:00 75:00-80:00
The lecture revisits Class D addresses. The instructor writes 'Class-D - Reserved for IPv4 multicasting'. He explains that multicasting means sending a single data stream to multiple devices at once. He notes that Class D addresses cannot be assigned to any system and there is no clear division of network and host parts, hence no mask.
85:00 – 90:00 80:00-85:00
The instructor discusses Class E addresses. He writes 'Class E is used in research'. He lists the users: protocol researchers, OS developers, network equipment vendors, and cybersecurity researchers. He explains that Class E addresses are reserved for future use and experimental purposes. They are not assigned to any standard system.
90:00 – 95:00 85:00-90:00
The lecture covers the DHCP protocol. The instructor writes 'DHCP - Dynamic Configuration Protocol'. He explains its purpose is to get an IP automatically when you connect to a WiFi or wired connection. He notes that DHCP gives IP addresses to devices automatically and is used in home networks, offices, and universities.
95:00 – 100:00 90:00-95:00
The instructor explains the DHCP server. He writes 'DHCP Server is often is our router/gateway'. He mentions that the DHCP server maintains a pool of IP addresses and assigns them to devices as they connect. He also notes that the range 0.0.0.0 to 0.255.255.255 is reserved and not assigned to any host.
100:00 – 105:00 95:00-100:00
The lecture discusses the evolution of IP configuration protocols. The instructor writes 'RARP - BOOTP - DHCP' and marks DHCP as the latest. He explains that RARP (Reverse ARP) was used to get an IP from a MAC address, and BOOTP was an improvement. DHCP is the current standard for dynamic IP assignment.
105:00 – 110:00 100:00-105:00
The instructor explains the DHCP process. He draws a diagram showing a client, a gateway, and a pool. He writes 'MAC, IP' and '0.0.0.0' to indicate the initial state of a client. When a client connects, it broadcasts a request, and the DHCP server responds with an available IP from the pool.
110:00 – 115:00 105:00-110:00
The lecture covers the ARP broadcast in detail. The instructor writes 'A will broadcast a ARP packet in its own network to get MAC of B'. He gives an example: 'Who has 202.192.63.218? Reply'. This broadcast is sent to all devices in the local network. Only the device with the matching IP will respond.
115:00 – 117:36 110:00-115:00
The instructor concludes the lecture by summarizing the key points. He reviews the importance of subnetting for network management, the role of ARP in local communication, and the use of loopback addresses for testing. He emphasizes that understanding these concepts is crucial for network administration and troubleshooting. The session ends with a brief Q&A.
The lecture systematically builds knowledge from basic IP addressing to advanced network concepts. It starts with Class C and B addresses, establishing the foundation of network and host bits. The instructor then introduces subnetting as a solution for network management, using practical examples to show how masks affect the number of subnets and hosts. The discussion extends to Class D and E addresses, highlighting their specialized uses in multicasting and research. Finally, the lecture covers essential protocols like ARP and DHCP, explaining their roles in resolving addresses and assigning IPs dynamically. The use of diagrams and step-by-step calculations reinforces the theoretical concepts, making the material accessible for students preparing for networking exams.