Practical - 73 :- Installing Proxy Servers

Proxy Servers

What is a proxy server? It’s a mediator or a replacement server. It allows your computer to connect to the internet using a different IP address. In simple terms, proxy servers add an extra layer of privacy to your online presence and can also save a lot of bandwidth in certain situations.

When using a proxy, internet traffic and files can be compressed, and all the unnecessary parts can be left aside (e.g., annoying ads on web pages). Proxies are very useful to companies with a large number of employees on the same wireless network, as they can ease the bandwidth traffic of a single address.

How to Connect to a Proxy Server on Windows

There are two basic ways you can connect to a proxy server on a Windows computer. One is with an automated script, and the other method is manual. Let’s start with the instructions for using the script:

Step - I :- On your computer, go to Start > Settings.

Step - II :- Click on the Network & Internet option. 

Step - III :- Within the side menu, click on Proxy.

Step - IV :- Enable the Use setup script option.

Step - V :- Enter the script address you were given (by your employer, school, or another server owner.) and select Save. You can then exit the settings, and the script should become effective immediately.

The other way around is connecting to a proxy server manually:

1.     Enable Use a proxy server under the Manual proxy setup section.

2.     Enter the IP under the Address tab, and the Port number in the appropriate field.

3.     When you’re done, Save the changes and exit this menu.

 

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Practical -72 :- Configuring DHCP on Router

 

AIM :- Configuring DHCP on Router

DHCP stands for Dynamic Host Configuration Protocol. It is a service which allows you to configure TCP/ IP settings such as IP address and subnet mask on the clients (PC, laptop, printer, etc.) automatically. Typically, DHCP is configured on a dedicated server for better performance. The server can be either Windows-based or Linux-based.

To perform this exercise, we will use the following topology.

First, add the required devices in Cico Packet Tracer and connect them appropriately. In the preceding topology, Router1 will act as DHCP server while Router2 and PC1 will act as DCHP clients. Let’s begin the exercise.

Configuring DHCP on Router

DHCP stands for Dynamic Host Configuration Protocol. It is a service which allows you to configure TCP/ IP settings such as IP address and subnet mask on the clients (PC, laptop, printer, etc.) automatically. Typically, DHCP is configured on a dedicated server for better performance. The server can be either Windows-based or Linux-based.

To perform this exercise, we will use the following topology.

First, add the required devices in Cico Packet Tracer and connect them appropriately. In the preceding topology, Router1 will act as DHCP server while Router2 and PC1 will act as DCHP clients. Let’s begin the exercise.

Configuring DHCP on Router

DHCP stands for Dynamic Host Configuration Protocol. It is a service which allows you to configure TCP/ IP settings such as IP address and subnet mask on the clients (PC, laptop, printer, etc.) automatically. Typically, DHCP is configured on a dedicated server for better performance. The server can be either Windows-based or Linux-based.

To perform this exercise, we will use the following topology.

First, add the required devices in Cico Packet Tracer and connect them appropriately. In the preceding topology, Router1 will act as DHCP server while Router2 and PC1 will act as DCHP clients. Let’s begin the exercise.

1. On Router1, execute the following commands to configure an IP address.
   
   
   
2. Next, create a DHCP pool named DhcpPool1. Use 10.0.0.1 IP address as the default gateway and DNS server. Use 10.0.0.0 255.0.0.0 as network ID.     
   
   
   
   By default DHCP server will start to assign IP addresses from the first IP address of the assigned network ID and it will be 10.0.0.1/ 8. However, we have already configured this IP addresses manually on Fa0/ 0 interface of Router1. To avoid the confliction between DHCP assigned and manually assigned IP addresses, you can exclude one or more specific IP addresses or IP ranges from the DHCP pool. DHCP server will not distribute these IP addresses to any of the DHCP client.
3. The following commands will exclude 10.0.0.0.1 to 10.0.0.100 IP addresses that will not be distributed by DHCP server. 
   
   
   
4. On Router2, we will assign an IPv4 address on the Fa0/ 0 interface through the DHCP server. To do this, execute the following commands.  
   
   
   
5. Wait for a few seconds and then execute the following command to view the IP address on Router2. 
   
   
   
6. Once you have configured an IP address on Router2, switch to PC1, and try to obtain TCP/ IP settings through the DHCP server. To do so, open the console of PC1, select the Desktop tab. On the available options, click IP Configuration and then select the DHCP radio button.
7. After a few seconds, DHCP server will assign an IP address from the configured DHCP pool along with a default gateway and DNS server IP addresses. 
   
   
   
8. In the preceding figure, you can see that 10.0.0.102 IP address has been assigned by the DHCP server.
9. To verify the connectivity between PC1 and Router1, execute the following command at the Command Prompt window. 
   
   
   
10. You should be able to ping successfully, as shown in the following figure. 
    
    
    
11.  Save the configuration of each device and also save the topology and name is as DHCP Topology

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Theory -80 :- DHCP - AN INTRODUCTION

 

DHCP - AN INTRODUCTION

The Dynamic Host Configuration Protocol (DHCP) is a network protocol that is used to configure network devices so that they can communicate on an IP network. A DHCP client uses the DHCP protocol to acquire configuration information, such as an IP address, a default route and one or more DNS server addresses from a DHCP server. The DHCP client then uses this information to configure its host. Once the configuration process is complete, the host is able to communicate on that internet. The DHCP server maintains a database of available IP addresses and configuration information. When it receives a request from a client, the DHCP server determines the network to which the DHCP client is connected, and then allocates an IP address or prefix that is appropriate for the client, and sends configuration information appropriate for that client.

Because the DHCP protocol must work correctly even before DHCP clients have been configured, the DHCP server and DHCP client must be connected to the same network link. In larger networks, this is not practical. On such networks, each network link contains one or more DHCP relay agents. These DHCP relay agents receive messages from DHCP clients and forward them to DHCP servers. DHCP servers send responses back to the relay agent, and the relay agent then sends these responses to the DHCP client on the local network link.

DHCP servers typically grant IP addresses to clients only for a limited interval. DHCP clients are responsible for renewing their IP address before that interval has expired, and must stop using the address once the interval has expired, if they have not been able to renew it. DHCP is used for IPv4 and IPv6. While both versions serve much the same purpose, the details of the protocol for IPv4 and IPv6 are sufficiently different that they may be considered separate protocols.

Hosts that do not use DHCP for address configuration may still use it to obtain other configuration information. Alternatively, IPv6 hosts may use stateless address auto configuration. IPv4 hosts may use link-local addressing to achieve limited local connectivity.

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Theory -75 :- Overview Of Virtual , Trunkling -VLAN Trunk Protocol (VTP)

What is VLAN?

VLAN is a custom network which is created from one or more local area networks. It enables a group of devices available in multiple networks to be combined into one logical network. The result becomes a virtual LAN that is administered like a physical LAN. The full form of VLAN is defined as Virtual Local Area Network.

The below topology depicts a network having all hosts inside the same virtual LAN:

Without VLANs, a broadcast sent from a host can easily reach all network devices. Each and every device will process broadcast received frames. It can increase the CPU overhead on each device and reduce the overall network security.

In case if you place interfaces on both switches into separate VLAN, a broadcast from host A can reach only devices available inside the same VLAN. Hosts of VLANs will not even be aware that the communication took place. This is shown in the below picture:

 

VLAN in networking is a virtual extension of LAN. A LAN is a group of computer and peripheral devices which are connected in a limited area such as school, laboratory, home, and office building. It is a widely useful network for sharing resources like files, printers, games, and other applications.

How VLAN works

Here is a step by step detail of how VLAN works:

• VLANs in networking are identified by a number.
• A Valid range is 1-4094. On a VLAN switch, you assign ports with the proper VLAN number.
• The switch then allows data which needs to be sent between various ports having the same VLAN.
• Since almost all networks are larger than a single switch, there should be a way to send traffic between two switches.
• One simple and easy way to do this is to assign a port on each network switch with a VLAN and run a cable between them.

 

Example of VLAN

In the below example, there are 6 hosts on 6 switches having different VLANs. You      need 6 ports to connect switches together. It means, if you have 24 various VLANs,        you will have only 24 hosts on 45 port switches.

Characteristics of VLAN

Here are the important characteristics of VLAN:

• Virtual LANs offer structure for making groups of devices, even if their networks are different.
• It increases the broadcast domains possible in a LAN.
• Implementing VLANs reduces the security risks as the number of hosts which are connected to the broadcast domain decreases.
• This is performed by configuring a separate virtual LAN for only the hosts having sensitive information.
• It has a flexible networking model that groups users depending on their departments instead of network location.
• Changing hosts/users on a VLAN is relatively easy. It just needs a new port-level configuration.
• It can reduce congestion by sharing traffic as individual VLAN works as a separate LAN.
• A workstation can be used with full bandwidth at each port.
• Terminal reallocations become easy.
• A VLAN can span multiple switches.
• The link of the trunk can carry traffic for multiple LANs.

 

Types of VLANs

Here are the important types of VLANs

 

Port-Based VLAN

Port-based VLANs groups virtual local area network by port. In this type of virtual LAN, a switch port can be configured manually to a member of VLAN.

Devices that are connected to this port will belong to the same broadcast domain that is because all other ports are configured with a similar VLAN number.

The challenge of this type of network is to know which ports are appropriate to each VLAN. The VLAN membership can’t be known just by looking at the physical port of a switch. You can determine it by checking the configuration information.

 

Protocol Based VLAN

This type of VLAN processes traffic based on a protocol that can be used to define filtering criteria for tags, which are untagged packets.

In this Virtual Local Area Network, the layer-3 protocol is carried by the frame to determine VLAN membership. It works in multi-protocol environments. This method is not practical in a predominately IP based network.

 

MAC Based VLAN

MAC Based VLAN allows incoming untagged packets to be assigned virtual LAN and, thereby, classify traffic depending on the packet source address. You define a Mac address to VLAN mapping by configuring mapping the entry in MAC to the VLAN table.

This entry is specified using source Mac address proper VLAN ID. The configurations of tables are shared among all device ports.

Advantages of VLAN

Here are the important pros/benefits of VLAN:

• It solves a broadcast problem.
• VLAN reduces the size of broadcast domains.
• VLAN allows you to add an additional layer of security.
• It can make device management simple and easier.
• You can make a logical grouping of devices by function rather than location.
• It allows you to create groups of logically connected devices that act like they are on their own network.
• You can logically segment networks based on departments, project teams, or functions.
• VLAN helps you to geographically structure your network to support the growing companies.
• Higher performance and reduced latency.
• VLANs provide increased performance.
• Users may work on sensitive information that must not be viewed by other users.
• VLAN removes the physical boundary.
• It lets you easily segment your network.
• It helps you to enhance network security.
• You can keep hosts separated by VLAN.
• You do not require additional hardware and cabling, which helps you to saves costs.
• It has operational advantages because of changing the IP subnet of the user is in software.
• It reduces the number of devices for particular network topology.
• VLAN makes managing physical devices less complex.

Disadvantages of VLAN

Here are the important cons/ drawbacks of VLAN:

A packet can leak from one VLAN to other.

An injected packet may lead to a cyber-attack.

Threat in a single system may spread a virus through a whole logical network.

You require an additional router to control the workload in large networks.

You can face problems in interoperability.

A VLAN cannot forward network traffic to other VLANs.

Application/Purpose of VLAN

Here are the important uses of VLAN:

• VLAN is used when you have 200+ devices on your LAN.
• It is helpful when you have a lot of traffic on a LAN.
• VLAN is ideal when a group of users need more security or being slow down by many broadcasts.
• It is used when users are not on one broadcast domain.
• Make a single switch into multiple switches.

Summary:

• VLAN is defined as a custom network which is created from one or more local area networks.
• VLAN in networking are identified by a number.
• A Valid range is 1-4094. On a VLAN switch, you assign ports with the proper VLAN number.
• Virtual LANs offer structure for making groups of devices, even if their networks are different.
• The main difference between LAN and VLAN is that In LAN, the network packet is advertised to each and every device Whereas in VLAN, the network packet is sent to only a specific broadcast domain.
• The primary advantage of VLAN is that it reduces the size of broadcast domains.
• The drawback of VLAN is that an injected packet may lead to a cyber-attack.
• VLAN is used when you have 200+ devices on your LAN.

 

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Theory -74.1 :- IP Addressing ,Types of IP Address And Classful Addressing

IP Addressing  

IP Address is short for Internet Protocol Address.

• It is a unique address assigned to each computing device in an IP network.
• ISP assigns IP Address to all the devices present on its network.
• Computing devices use IP Address to identify and communicate with other devices in the IP network.

Types of IP Address

IP Addresses may be of the following two types

 

 

1. Static IP Address-

• Static IP Address is an IP Address that once assigned to a network element Always remains the same.
• They are configured manually.
• Some ISPs do not provide static IP addresses.
• Static IP Addresses are more costly than dynamic IP Addresses

2. Dynamic IP Address

Dynamic IP Address is a temporarily assigned IP Address to a network element.

• It can be assigned to a different device if it is not in use.
• DHCP or PPPoE assigns dynamic IP addresses.

IP Address Format

IP Address is a 32 bit binary address written as 4 numbers separated by dots.

The 4 numbers are called as octets where each octet has 8 bits.

The octets are divided into 2 components- Net ID and Host ID.

Rules for assigning Host ID:

The Host ID is used to determine the host within any network. The Host ID is assigned based on the following rules:

• The Host ID must be unique within any network.
• The Host ID in which all the bits are set to 0 cannot be assigned as it is used to represent the network ID of the IP address.
• The Host ID in which all the bits are set to 1 cannot be assigned as it is reserved for the multicast address.

Rules for assigning Network ID:

If the hosts are located within the same local network, then they are assigned with the same network ID. The following are the rules for assigning Network ID:

• The network ID cannot start with 127 as 127 is used by Class A.
• The Network ID in which all the bits are set to 0 cannot be assigned as it is used to specify a particular host on the local network.
• The Network ID in which all the bits are set to 1 cannot be assigned as it is reserved for the multicast address.

Classes of IP Address-

All the classes of IP Address are summarized in the following table

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