Final Examination (Router Configuration)

An octet is a group of 8 bits, so there are 8 bits in an octet.

Unicast refers to a one-to-one type of communication where data is sent from a single sender to a specific recipient. In this type of communication, the sender and receiver are uniquely identified, and the data is intended for the specific recipient only. Therefore, the statement "Unicast is considered a one-to-one type of communication" is true.

SMTP (Simple Mail Transfer Protocol) is a protocol used for sending email messages between servers. The correct answer is 25 because port 25 is the default port number used by SMTP for communication. When an email client wants to send an email, it connects to the SMTP server on port 25 to initiate the email transfer process. This port is specifically reserved for SMTP traffic, allowing servers to communicate and relay emails across the internet.

The given correct answer, Transmission Control Protocol (TCP), is the transport protocol responsible for managing individual conversations between web servers and web clients. TCP ensures reliable and ordered delivery of data packets, establishes and maintains connections, and handles flow control. It breaks down data into smaller packets, sends them across the network, and reassembles them at the receiving end. TCP guarantees that all packets are received and in the correct order, making it suitable for applications like web browsing, file transfer, and email.

The correct answer is Internet Protocol (IP) because it is responsible for taking the formatted segments from TCP, encapsulating them into packets, assigning them the appropriate addresses, and delivering them across the best path to the destination host. IP is a network layer protocol that provides the addressing and routing functions necessary for data transmission over the internet. It ensures that data is properly packaged and sent to the correct destination, allowing for reliable communication between hosts.

The access layer of the hierarchical design model provides a means of connecting devices to the network and controlling which devices are allowed to communicate on the network. This layer is responsible for enforcing security policies, managing user access, and providing connectivity for end devices. It acts as a gateway between the end devices and the rest of the network, allowing only authorized devices to access the network resources.

Redundancy refers to the duplication of critical components or systems in order to provide backup or failover in case of failure. This ensures that there is no single point of failure and the system can continue to function even if one component fails. Redundancy enhances the reliability and availability of the system. It is an important factor in ensuring continuous operation and minimizing downtime.

Configuring communication between devices on different VLANs requires the use of Layer 3 of the OSI model. Layer 3, also known as the network layer, is responsible for routing and forwarding data packets between different networks. VLANs are virtual LANs that allow for logical segmentation of a network, and to enable communication between devices on different VLANs, a router or Layer 3 switch is required to route the traffic between the VLANs.

An access layer LAN switch uses Layer 2 of the OSI model to make a forwarding decision. Layer 2, also known as the Data Link Layer, is responsible for the reliable transfer of data between adjacent network nodes. It uses MAC addresses to identify devices on the network and determines how data is transmitted over the physical network. The access layer switch uses this layer to examine the MAC addresses of incoming frames and make decisions on where to forward them based on the destination MAC address.

The given IP address 192.168.242.5/20 has a subnet mask of 20 bits, which means the first 20 bits of the IP address are the network address and the remaining 12 bits are for host addresses. In this case, the network address is 192.168.240.0. The broadcast address is the highest address in the network, so by setting all the host bits to 1, we get the broadcast address of 192.168.255.255.

A wireless access point is a device that enables end devices to connect to a wireless network. It consists of a radio transmitter that allows for wireless communication between the access point and the end devices. This device acts as a bridge between the wired and wireless networks, providing a wireless connection to devices that do not have built-in wireless capabilities. It allows for seamless connectivity and communication between devices without the need for physical cables.

The net ID for the network in which 192.168.242.5/20 is located is 192.168.240.0. This is because the /20 subnet mask indicates that the first 20 bits of the IP address are the network portion, leaving the remaining 12 bits for the host portion. Therefore, the network ID is obtained by setting the host portion to all zeros, resulting in 192.168.240.0.

The core layer of the hierarchical network design model is referred to as the high-speed backbone of the internetwork, where high availability and redundancy are critical. This layer is responsible for transporting large amounts of data quickly and efficiently between different parts of the network. It ensures that there is enough bandwidth to support the traffic flow and provides redundancy to ensure uninterrupted connectivity in case of failures.

The distribution layer in a hierarchical design model controls the flow of network traffic using policies and performs routing functions between virtual LANs (VLANs). This layer helps to separate broadcast domains and provides a centralized point for implementing security policies, filtering traffic, and managing network resources. It acts as an intermediary between the access layer and the core layer, ensuring efficient and scalable network connectivity.

/28 represents the subnet mask or network prefix length in IP addressing. It indicates that the first 28 bits of the IP address are used to identify the network portion, while the remaining bits are used for the host portion. The subnet mask helps in dividing the IP address into network and host parts, allowing for efficient routing and addressing within a network.

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During data transfer, the receiving host is responsible for two things: acknowledgement and reassembly. Acknowledgement refers to the process of confirming that the data has been received successfully by sending a response back to the sender. Reassembly involves reconstructing the received data packets in the correct order to form the original message or file. Both of these tasks are crucial for ensuring reliable and accurate data transfer between the sender and the receiver.

End systems use port numbers to select the proper applications. Port numbers range from 0 to 65535, with the first 1024 ports being well-known ports that are reserved for specific services. The lowest port number that can be dynamically assigned by the host system is 1.

193.103.20.0 Need 50 Networks

128 64 32 16 8 4 2 1

0 0 1 1 0 0 1 0 = 50 in binary
Need to borrow 6 bits for # of Networks

New Subnet Mask = 255.255.255.11111100 (252) or /30
^ Increment = 4

2^6 = # of Networks = 64
2^2-2 = # of Hosts per Network = 2

First 5 IP Ranges
193.103.20.0 - 193.103.20.3
20.4 – 20.7
20.8 – 20.11
20.12 – 20.15
20.16 – 20.19

TCP/UDP port numbers are used to track the different conversations crossing the network at the same time. Each network connection is assigned a unique port number, which allows the network devices to differentiate between different conversations or applications running simultaneously. By tracking the port numbers, the network can correctly route the incoming data packets to the appropriate application or conversation. This enables multiple applications to communicate over the network concurrently without interference or confusion.

Router A receives 3 subnets: 172.16.64.0/18, 172.16.32.0/24 and 172.16.128.0/18.

All these 3 subnets have the same form of 172.16.x.x so our summarized subnet must be also in that form -> Only A, B or C is correct.

The smallest subnet mask of these 3 subnets is /18 so our summarized subnet must also have its subnet mask equal or smaller than /18.

-> Only answer A has these 2 conditions -> A is correct.

The TCP window size refers to the amount of data that can be sent by the sender without receiving an acknowledgment from the receiver. If packets are lost during transmission, the window size is decreased to prevent further congestion and ensure reliable delivery. This allows the sender to adjust the rate at which it sends data based on the network conditions and the receiver's ability to handle the incoming data.

Link aggregation should be implemented at the access, distribution, and core layers of the hierarchical network. This is because link aggregation, also known as link bundling or EtherChannel, allows multiple physical links to be combined into a single logical link. By implementing link aggregation at all three layers, the network can benefit from increased bandwidth, improved redundancy, and load balancing across multiple links. This ensures that all layers of the network can handle the aggregated traffic efficiently and effectively.

A firewall appliance is a device that is used to secure a network by controlling and monitoring incoming and outgoing network traffic. It acts as a barrier between a trusted internal network and an untrusted external network, such as the internet. The firewall appliance secures outgoing traffic by inspecting and filtering the data packets leaving the network, ensuring that only authorized and safe traffic is allowed. It also restricts incoming traffic by examining and blocking any suspicious or potentially harmful traffic from entering the network, thus protecting the internal network from external threats.

130.13.0.0 Need 500 Networks

128 64 32 16 8 4 2 1 . 128 64 32 16 8 4 2 1

0 0 0 0 0 0 0 1 . 1 1 1 1 0 1 0 0 = 500 in binary
Need to borrow 9 bits for # of Networks

New Subnet Mask = 255.255.11111111.10000000 (255.128) or /25
^ Increment = 128

2^9 = # of Networks = 512
2^7-2 = # of Hosts per Network = 126

First 5 IP Ranges
130.13.0.0 - 130.13.0.127
13.0.128 – 13.0.255
13.1.0 – 13.1.127
13.1.128 – 13.1.255
13.2.0 – 13.2.127

The hierarchical network model provides several benefits. Firstly, it reduces contention for bandwidth by dividing the network into smaller segments, allowing for better traffic flow and reducing congestion. Secondly, it increases fault tolerance of the network by providing redundancy at different levels, ensuring that if one component fails, the network can still function. Lastly, it simplifies management and troubleshooting by organizing the network into distinct layers, making it easier to identify and resolve issues.

VLAN 2 has 114 hosts so we need to leave 7 bits 0 for the host addresses (27 – 2 = 126 > 114). Notice that we are working with class B (both Host A and Host B belong to class B) and the default subnet mask of class B is /16 so we need to use 16 – 7 = 9 bits 1 for the sub-network mask, that means the subnet mask should be 255.255.255.128 -> B is correct.

By using above scheme, C is correct because the IP 172.16.1.25 belongs to the sub-network of VLAN 1 (172.16.1.0/25) and can be assigned to hosts in VLAN 1.

For communication between VLAN 1 and VLAN 2, the LAN interface of the router should be divided into multiple sub-interfaces with multiple IP addresses -> F is correct.

150.20.0.0 Need 500 Hosts per Network

128 64 32 16 8 4 2 1 . 128 64 32 16 8 4 2 1

0 0 0 0 0 0 0 1 . 1 1 1 1 0 1 0 0 = 500 in binary
Need to save 9 bits for # of Hosts

New Subnet Mask = 255.255.11111110.00000000 (254.0) or /23
^ Increment = 2 in the 3rd Octet

2^7 = # of Networks = 128
2^9-2 = # of Hosts per Network = 510

First 5 IP Ranges
150.20.0.0 - 150.20.1.255
20.2.0 – 20.3.255
20.4.0 – 20.5.255
20.6.0 – 20.7.255
20.8.0 – 20.9.255

At all three levels of the Cisco three-layer hierarchical model, Power over Ethernet (PoE) is supported. PoE allows devices to receive power and data over the same Ethernet cable, eliminating the need for separate power sources. Quality of Service (QoS) is also supported at all three levels, allowing for prioritization and management of network traffic to ensure optimal performance. Link aggregation, which involves combining multiple physical links into a single logical link, is the third feature supported at all three levels. This helps increase bandwidth and redundancy.