What is Frame Relay & Its Benifits

What is Frame Relay & Its Benifits

This chapter is on What is Frame Relay & Its Benifits. Frame Relay is an alternative to dedicated WAN leased lines, which are more expensive. This section describes the benefits of Frame Relay. Frame Relay is a high performance WAN protocol that works on the physical and data link layers of the OSI reference model. While more modern services such as broadband and metropolitan Ethernet reduced the need for Frame Relay in many locations, Frame Relay is still a viable option in many sites around the world.

FRAME RELAY TECHNOLOGY

Leased lines provide permanent dedicated capacity and are widely used to build WAN networks. They are the traditional connection of preference, but have a number of disadvantages.
A disadvantage is that customers pay for leased lines with a fixed capacity . However, WAN traffic usually varies, and some of the capacity remains unused. In addition, each terminal needs an individual physical interface on the router, which increases equipment costs. In general, any change in the leased line requires that the staff of the service provider visit the site.
Frame Relay is a high performance WAN protocol that works on the physical and data link layers of the OSI reference model. Unlike leased lines, Frame Relay only requires a single access circuit to the Frame Relay service provider to communicate with other sites connected to the same provider. The capacity between two sites may vary.
Eric Scace, a Sprint International engineer, invented Frame Relay as a simpler version of the X.25 protocol for use through the integrated services digital network (ISDN) interfaces. Currently, it is also used in other types of network interfaces. When Sprint implemented Frame Relay in its public network, it used StrataCom switches. The acquisition of StrataCom by Cisco in 1996 marked its entry into the market of service providers.

FRAME RELAY USEs

Network service providers implement Frame Relay to support voice and data traffic between LAN networks through a WAN. Each end user obtains a private line, or a leased line, to a Frame Relay node.
The Frame Relay network handles transmission through a frequently changing route, transparent to all end users. As shown in Image, Frame Relay provides a solution to allow communications between several sites through a single access circuit to the provider.

Historically, Frame Relay was widely used as a WAN protocol because it was economical compared to dedicated leased lines. In addition, configuring the user's equipment in a Frame Relay network is very simple.
Frame Relay connections are created by configuring the routers or other devices on the client's local computer (CPE) so that they communicate with a Frame Relay switch from a service provider. The service provider configures the Frame Relay switch, which minimizes the configuration tasks of the end user.

BENEFITS OF FRAME RELAY WAN TECHNOLOGY

With the advent of broadband services such as DSL and cable modem, Ethernet WAN, VPN and multi-protocol tag switching (MPLS), Frame Relay became a less suitable solution to access the WAN. However, there are still sites in the world that rely on Frame Relay to get connectivity to the WAN.
Frame Relay provides more bandwidth, reliability and resistance than private or leased lines.
Using an example of a large business network helps illustrate the benefits of using a Frame Relay WAN . In the example shown in Image, the SPAN Engineering company has five campuses throughout North America. Like most organizations, SPAN has various bandwidth requirements.

The first thing to keep in mind is the bandwidth requirement of each site . When working in the head office, connecting Chicago to New York requires a maximum speed of 256 kb / s. Three other sites need a maximum speed of 48 kb / s to connect to the central office, while the connection between the New York and Dallas branches requires only 12 kb / s.

REQUIREMENTS OF THE DEDICATED LINE

Through the leased lines, each of the SPAN sites is connected through a switch in the central office (CO) of the local telephone company through the local loop, and then through the entire network.
The Chicago and New York sites use a dedicated T1 line (equivalent to 24 DS0 channels) to connect to the switch, while other sites use ISDN connections (56 kb / s), as shown in Image 3.

Because the Dallas site connects to New York and Chicago, it has two locally leased lines. Network service providers provide SPAN with a DS0 between the respective COs, except for the largest pipeline that connects Chicago and New York, and has four DS0s.
The DS0 have different prices according to the region and are generally offered at a fixed price. These lines are really dedicated, since the network service provider reserves that line for SPAN exclusive use. There is no sharing, and SPAN pays for the end-to-end circuit, regardless of how much bandwidth it uses.

DISADVANTAGES OF DEDICATED LINES

A dedicated line provides few practical opportunities to establish a one-to-many connection without obtaining more lines from the network service provider. In the example, almost all communication must flow through the company's headquarters, simply to reduce the cost of additional lines.

• After a more detailed analysis of the bandwidth requirements for each site, it is verified that there is a lack of efficiency:
• Of the 24 DS0 channels available on the T1 connection, the Chicago site uses only seven. Some service providers offer fractional T1 connections in increments of 64 kb / s, but this requires a specialized device called a “multiplexer” at the client end to channel the signals. In this case, SPAN opted for the full T1 service.
• Similarly, the New York site uses only five of its 24 available DS0s.
• Because Dallas must connect to Chicago and New York, there are two lines that connect to each site through the CO.

The leased line design also limits flexibility. Unless the circuits are already installed, connecting new sites usually requires new circuit installations, and implementing it takes a long time. From the point of view of network reliability, imagine the additional costs in money and the complexity of adding redundant replacement circuits.

PROFITABILITY AND FLEXIBILITY OF FRAME RELAY

The SPAN Frame Relay network uses permanent virtual circuits (PVC), as shown in following image.

A PVC is the logical path along a source Frame Relay link, through the network and along a Frame Relay termination link to its final destination. Compare this to the physical path that a dedicated connection uses.
In a network with access through Frame Relay, a PVC defines the route between two terminals exclusively. The concept of virtual circuits (VC) is discussed in more detail later in this section.
SPAN Frame Relay solution provides flexibility and profitability.

FRAME RELAY PROFITABILITY

Frame Relay is a more profitable option for two reasons.

• First, with dedicated lines, customers pay for an end-to-end connection that includes the local loop and network link. With Frame Relay, customers only pay for the local loop and acquire the bandwidth of the network service provider.

The distance between the nodes is not important. In a dedicated line model, customers use dedicated lines provided in increments of 64 kb / s, and Frame Relay customers can define their virtual circuit needs with much greater granularity, often in increments as small as 4 kb / s.

• The second reason for the profitability of Frame Relay is that it shares bandwidth through a larger customer base. Generally, a network service provider can serve 40 or more clients of 56 kb / s through a T1 circuit.

The use of dedicated lines would require more CSU / DSU (one for each line), as well as more complicated routing and switching. Network service providers save because there is less equipment to acquire and maintain.

THE FLEXIBILITY OF FRAME RELAY

A virtual circuit provides considerable flexibility in network design. By analyzing the illustration, you can see that all SPAN offices connect to the Frame Relay cloud through their respective local loops. At the moment, what happens in the cloud is really not of interest.
The only thing that matters is that when any SPAN office wishes to communicate with any other SPAN office, all it has to do is connect to a virtual circuit that leads to the other office.
In Frame Relay, the end of each connection has a number to identify it called " data link connection identifier " (DLCI). Any station can connect to any other by simply indicating the address of that station and the DLCI number of the line to be used.
In a later section, you will learn that when Frame Relay is configured, all data from all configured DLCIs flow through the same router port. Imagine the same flexibility through dedicated lines. Not only is it difficult, but it also requires many more equipment.

Cisco Enterprise Network Architecture

Cisco Enterprise Network Architecture

This section explains the various modules in the network design and describes the Cisco enterprise architecture model . The benefits obtained through a systematic design approach are also covered.

MODULAR NETWORK DESIGN

While the hierarchical network design works well within the campus infrastructure, the networks expanded beyond these borders. As shown in Image 1, the networks became more sophisticated and complex, and some require connections to dedicated data centers, which are usually external.

Often, branches require connectivity to campus backbones, and employees need to be able to work from their home offices or other remote locations. Because the complexity of the network to meet these demands increased, it became necessary to modify the design of the network by one that used a more modular approach.
A modular network design separates the network into several functional network modules, and each of these points to a specific place or purpose in the network. The modules represent areas that have a different physical or logical connectivity. They are responsible for designating where the different functions are carried out in the network.
The modular approach has several benefits:

• Faults that occur within a module can be isolated from the rest of the network, allowing for easier problem detection.
• Changes, updates or the introduction of new network services can be carried out in a controlled and gradual manner, allowing greater flexibility in the maintenance and operation of the campus network.
• When a specific module no longer has sufficient capacity or does not have a new function or service, it can be updated or replaced with another module that has the same structural function in the general hierarchical design.
• Security can be implemented modularly.

MODULES IN BUSINESS ARCHITECTURE

The modular approach applied to the network design further divides the three-layer hierarchical design, since it eliminates specific blocks or modular areas. These basic modules are connected to each other through the core of the network.

The basic network modules include the following:

• Access and distribution : also called “distribution block”, it is the best known element and the fundamental component of campus design ( orange frame ).
• Services : This is a generic block that is used to identify services such as the centralized wireless controllers of the Lightweight Access Point Protocol (LWAPP), the unified communications services, the policy gateways, among others ( celestial framework ).
• Data center : originally, it was called "server farm". This block is responsible for managing and maintaining many data systems that are critical to modern business operations. Employees, partners and customers rely on data and data center resources to create, collaborate and interact effectively ( green framework ).
• Business perimeter : consists of the perimeter Internet and the WAN perimeter. These blocks offer connectivity to voice, video and data services outside the company ( red frame ).

CISCO ENTERPRISE ARCHITECTURE MODEL

To meet the need for modularity in network design, Cisco developed the Cisco enterprise architecture model . This model provides all the benefits of hierarchical network design in campus infrastructure and facilitates the design of larger and scalable networks.
The Cisco enterprise architecture model separates the business network into functional areas that are known as "modules." The modularity that is incorporated into the architecture allows for flexibility in network design and facilitates its implementation and problem solving.
As shown in Image, the following are the main modules of the Cisco enterprise architecture:

• Business campus
• Enterprise Edge
• Service provider end

There are additional modules connected to the perimeter of the service provider:

• Company data center
• Company Branch
• Remote worker of the company

CISCO BUSINESS CAMPUS

A campus network is a building or group of buildings connected to a business network that consists of many LANs. Generally, a campus is limited to a fixed geographical area, but it can cover several neighboring buildings, for example, an industrial complex or the environment of an industrial park.
The business campus module describes the recommended methods for creating a scalable network, while addressing the needs of commercial operations of the campus type. The architecture is modular and can be easily expanded to include additional buildings or campus floors as the company grows.
The business campus module consists of the following submodules:

• Building access
• Building distribution
• Campus Core
• Data center

Together, these submodules do the following:

• They provide high availability through a robust hierarchical network design.
• They integrate IP communications, mobility and advanced security.
• They use multicast traffic and QoS to optimize network traffic.
• They provide greater security and flexibility by managing access, VLANs and VPNs with IPsec.
• The architecture of the business campus module provides the company with high availability through a robust multilayer design, redundant hardware and software features, and automatic procedures to reconfigure network routes when failures occur.

Integrated security protects against the impact of worms, viruses and other network attacks, in addition to mitigating it, even at the switch port level.
The data center sub-module typically contains internal corporate and email servers that provide application, archiving, printing, email and domain name system (DNS) services to internal users.

CISCO BUSINESS PERIMETER

The business perimeter module provides connectivity for voice, video and data services outside the company. Often, this module works as a link between the business campus module and the other modules.
The business perimeter module consists of the following submodules:

• E-commerce networks and servers : the e-commerce submodule allows companies to support e-commerce applications through the Internet.

They include web, application and database servers, firewall and firewall routers, and intrusion prevention systems (IPS) in the network.

• Internet connectivity and perimeter zone (DMZ) : The Internet sub-module of the business perimeter provides internal users with secure connectivity to Internet services, such as public servers, email and DNS. Connectivity is also provided to one or more Internet service providers (ISPs).

They include firewall and firewall routers, Internet perimeter routers, FTP and HTTP servers, SMTP relay servers and DNS servers.

• Remote access and VPN: The remote access and VPN sub-module of the business perimeter provides remote access termination services, including authentication for remote users and sites.

They include firewalls, dial-up hubs, Cisco Adaptive Security Devices (ASA) and intrusion prevention system (IPS) applications on the network.

WAN : The WAN submodule uses various WAN technologies to route traffic between remote sites and the central site.
They include technologies such as multi-protocol tag switching (MPLS), metropolitan Ethernet, leased lines, synchronous optical network (SONET) and synchronous digital hierarchy (SDH), PPP, Frame Relay, ATM, cable, digital subscriber line (DSL) and wireless technology.

SERVICE PROVIDER END

• Companies use service providers (SP) to link to other sites. The perimeter module of the SP may include the following:
• Internet service providers (ISP)
• WAN services, such as Frame Relay, ATM and MAN
• Public switched telephone network (PSTN) services
• The perimeter of the SP provides connectivity between the business campus module and the remote data center, branch and remote worker modules of the company.

The perimeter module of the SP has the following characteristics:

• It covers large geographic areas in a cost-effective manner.
• Converge voice, video and data services through a single IP communications network.
• Supports QoS and service level agreements.
• It supports VPN security (IPsec and MPLS) through the Layer 2 and Layer 3 WANs.
• Connection to an ISP

Redundant connections to a single ISP can include the following:

• Simple connection: a single connection to an ISP
• Double connection: two or more connections to a single ISP
• Connection to several ISPs

Redundancy can also be established with several ISPs, as shown in Image 5. The options for connecting to several ISPs include the following:

• Multiple host connection: connections to two or more ISPs
• Dual multiple host connection: multiple connections to two or more ISPs

REMOTE FUNCTIONAL AREA

The remote functional area is responsible for the remote connectivity options and includes several modules:

COMPANY BRANCH

The company's branch module includes remote branches that allow employees to work in off-campus locations.

• In general, these locations provide security, telephony and mobility options to employees, as well as general connectivity to the campus network and the various components located within the business campus.
• The company's branch module allows companies to extend applications and services from the head office, such as security, Cisco Unified Communications and advanced application performance, to remote branches.
• The perimeter device that connects the remote site to the central site varies according to the needs and size of the site.
• Large remote sites can use advanced technology Cisco Catalyst switches, while smaller sites can use an ISR G2 router. These remote sites depend on the perimeter of the SP to provide the services and applications of the main site.
• In Image, the company's branch module connects to the business campus primarily through a WAN link; however, it also has a backup internet link. The Internet link uses VPN technology with IPsec from site to site to encrypt corporate data.

REMOTE WORKER OF THE COMPANY

The company's remote worker module is responsible for providing connectivity to employees who work from various geographically dispersed locations, including domestic offices, hotels or customer sites.

• The remote worker module recommends that mobile users connect to the Internet through the services of a local ISP, such as the cable modem or DSL modem.
• VPN services can be used to protect communications between the mobile worker and the central campus.
• Integrated security and identity-based network services allow the company to extend campus security policies to the remote worker.
• Staff can log in to the network securely through the VPN and access authorized applications and services from a single cost-effective platform.

COMPANY DATA CENTER

The company's data center module is a data center with the same functional options as the campus data center, but in a remote location.

• This provides an additional layer of security, since the external data center can provide the company with disaster recovery and business continuity services.
• Advanced technology switches, such as Cisco Nexus series switches, use fast WAN services such as Metropolitan Ethernet (MetroE) to connect the business campus to the remote company's data center.
• Redundant data centers provide support through synchronous and asynchronous replication of data and applications. In addition, the network and devices offer load balancing of servers and applications to maximize performance. This solution allows the company to scale without major changes in infrastructure.

Hierarchical Network Design | Cisco Hierarchical Model

Hierarchical Network Design | Cisco hierarchical Model

This post describe the Hierarchical Network Design and principles of structured engineering for network design . You will learn the three layers of Cisco hierarchical Model and how they are used in network design. Network design start from analyzing the network component, it is useful to categorize the networks according to the number of devices served:

• Small network : provides services for up to 200 devices.
• Medium network : provides services for 200 to 1000 devices.
• Large network : provides services for more than 1000 devices.

Network designs vary according to the size and needs of organizations. There are many variables to consider when designing a network. Normally a large business network consisting of a main campus that connects small, medium and large sites. Network design is an expanding area and requires a lot of knowledge and experience. The objective of this section is to present widely accepted network design concepts.

PRINCIPLES OF STRUCTURED ENGINEERING

Regardless of the size or requirements of the network, a fundamental factor for the correct implementation of any network design is to follow good principles of structured engineering:

• Hierarchy : a hierarchical network model is a useful high-level tool for designing a reliable network infrastructure. Divide the complex problem of network design into smaller and easier to manage areas.
• Modularity : by separating in modules the various functions that exist in a network, it is easier to design. Cisco identified several modules, including the business campus, the service block, the data center and the Internet perimeter.
• Resistance : the network must be available so that it can be used both in normal conditions (maintenance periods) and abnormal conditions (hardware or software failures).
• Flexibility : the ability to modify parts of the network, add new services or increase capacity without the need for major updates (i.e. replace major hardware devices).

To meet these fundamental design objectives, the network must be built on the basis of a hierarchical network architecture that allows flexibility and growth.

Cisco Hierarchical Model

In network technology, a hierarchical design involves dividing the network into independent layers . Each layer (or level) in the hierarchy provides specific functions that define its function within the general network.
This helps the network designer and architect to optimize and select the appropriate network features, hardware and software to perform the specific functions of that network layer. Hierarchical models apply to LAN and WAN design.
A typical design of a corporate campus hierarchical LAN network includes the following three layers:

• Access layer : provides network access for workgroups and users.
• Distribution layer : provides policy-based connectivity and controls the boundary between the access and core layers.
• Core layer : provides fast transport between distribution switches within the business campus.

The benefit of dividing a flat network into smaller and easier to manage blocks is that local traffic remains local. Only traffic destined for other networks is moved to a higher layer.
Layer 2 devices in a flat network provide few opportunities to control broadcasts or filter unwanted traffic. As more devices and applications are added to a flat network, response times degrade until the network becomes unusable.

In Image, another example of a three-layer hierarchical network design is shown. Note that each building uses the same hierarchical network model that includes the access, distribution and core layers.

ACCESS LAYER

In a LAN environment, the access layer grants access to the network for the terminals. In the WAN environment, you can provide access to the business network for remote workers or remote sites through WAN connections.
As shown in Image, the access layer for a small business network usually incorporates Layer 2 switches and access points that provide connectivity between workstations and servers.

The access layer performs several functions, including the following:

• Layer 2 Switching
• High availability
• Port security
• Classification and marking of QoS, and confidence limits
• Address Resolution Protocol (ARP) Inspection
• Virtual access control lists (VACL)
• Expansion tree
• Auxiliary Ethernet and VLAN power for VoIP

DISTRIBUTION LAYER

The distribution layer aggregates the data received from the access layer switches before they are transmitted to the core layer for routing to its final destination. In Image 4, the distribution layer is the boundary between the layer 2 domains and the layer 3 routed network.
The distribution layer device is the center in wiring cabinets. To segment workgroups and isolate network problems in a campus environment, a multilayer router or switch is used.
A distribution layer switch can provide upstream services for many access layer switches.
The distribution layer can provide the following:

• LAN or WAN link aggregation.
• Policy-based security in the form of access control lists (ACLs) and filtering.
• Routing services between LAN and VLAN networks, and between routing domains (eg, EIGRP to OSPF).
• Redundancy and load balancing.
• A limit for aggregation and summarization of routes that is configured in the interfaces to the core layer.
• Broadcast domain control, since neither routers nor multilayer switches resend broadcasts. The device works as a demarcation point between broadcast domains.

Cisco CORE LAYER

The core layer is also known as " network backbone ." The core layer consists of high-speed network devices, such as Cisco Catalyst 6500 or 6800 switches. These are designed to switch packets as quickly as possible and interconnect various campus components, such as distribution modules, service modules, the center of data and the perimeter of the WAN.
As shown in above Image, the core layer is essential for interconnectivity between the distribution layer devices; for example, interconnects the distribution block to the perimeter of the WAN and the Internet.
The core must have high availability and must be redundant. The kernel aggregates traffic from all devices in the distribution layer, so it must be able to send large amounts of data quickly.
Some of the considerations regarding the core layer include the following:

• You must provide high speed switching (i.e. fast transport).
• It must provide reliability and fault tolerance.
• You must achieve scalability through faster teams, not more teams.
• You must avoid packet handling that implies a high demand for the CPU because of security, inspection, quality of service (QoS) classification or other processes.

TWO-LEVEL CONTRACTED CORE DESIGN

There are no absolute rules about how a campus network should be physically assembled. While it is true that many campus networks are built with three physical levels of switches, it is not a strict requirement. On a smaller campus, the network can have two levels of switches in which the core and distribution elements are combined into a physical switch. This is called "contracted core design."
The three-tier hierarchical design maximizes performance, network availability and the ability to scale the network design.
However, there are many small business networks that do not grow much over time. Therefore, a two-level hierarchical design in which the core and distribution layers are combined into a single layer is usually more practical. There is a "contracted core" when the functions of the distribution layer and the core layer are implemented by a single device. The main motivation to choose the contracted core design is the reduction of network costs, while maintaining the majority of the benefits of the three-tier hierarchical model.

Switch Types | How to Select Switch for your network

Switch Types | How to Select Switch for your Network

For designing a switch network the appropriate hardware features of the switch types are considered to support the requirements of your networks. This post will help you How to Select Switch for your network. When designing a network, it is important to select the appropriate hardware to meet the current requirements of the network, as well as to allow its growth. Within an enterprise network, both switches and routers play a very important role in network communication.If you want to learn how to choose a router for your network visit here.

Switch Categories

There are five categories of switches for business networks, which are shown in figure:

• Campus LAN switches : to scale network performance on an enterprise LAN, core, distribution, access and compact switches can be used. These switch platforms vary from fanless switches with eight fixed ports to 13-blade switches that support hundreds of ports. Campus LAN switch platforms include Cisco 2960, 3560, 3750, 3850, 4500, 6500 and 6800 series switches.
• Managed switches in the cloud : Access switches managed through the Cisco Meraki cloud allow virtual stacking of switches. These control and configure thousands of switch ports on the Web, without the intervention of the IT staff.
• Data center switches : data centers must be assembled based on switches that promote infrastructure scalability, continuity of operation and transport flexibility. The data center switch platforms include the Cisco Nexus and Cisco Catalyst 6500 series switches.
• Service provider switches: these switches are divided into two categories, aggregation switches and Ethernet access switches. Aggregation switches are service level Ethernet switches that add traffic to the perimeter of the network. The Ethernet access switches of service providers have application intelligence, unified services, virtualization, integrated security and simplified administration.
• Virtual networks : networks become increasingly virtual. Cisco Nexus virtual network switch platforms provide secure multi-tenant services by incorporating virtualization intelligence technology into the data center network.

Form factors

When selecting switches, network administrators must determine their form factors. This includes the features of fixed configuration (Left), modular configuration (Center), stackable (Right) and non-stackable. The thickness of the switch, which is expressed in the number of rack units, is also important in the case of switches that are mounted in a rack. For example, fixed configuration switches are all units of a rack (1U).

• Cost : the cost of a switch depends on the quantity and speed of the interfaces, the supported functions and the expandability.
• Port density : network switches must support an adequate number of devices on the network.
• Power : Today, it is common to power access points, IP phones and even compact switches using Ethernet power. Some rack-based switches support redundant power supplies.
• Reliability : the switch must provide continuous access to the network.
• Port speed: the speed of the network connection is one of the fundamental aspects for end users.
• Frame buffers : the ability of the switch to store frames is important in networks where there may be congested ports connected to servers or other areas of the network.
• Scalability : in general, the number of users in a network increases over time; therefore, the switch must provide the possibility of growth.

Density of Switch ports

The port density of a switch refers to the number of ports available on a single switch . The illustration shows the port density of three different switches.

• Fixed configuration switches generally support up to 48 ports on a single device. They feature options for up to four additional ports for small pluggable form factor (SFP) devices. High port densities allow better use of limited space and energy.

If there are two switches of 24 ports each, they could support up to 46 devices, since at least one of the ports of each switch is lost in the connection of each switch to the rest of the network. In addition, two power sockets are required.
On the other hand, if there is a single 48-port switch, 47 devices can be supported; In this case, a single port is used to connect the switch to the rest of the network and a single outlet to support the switch.

• Modular switches can support high port densities by adding several switch port line cards. For example, some Catalyst 6500 switches can support more than 1000 switch ports.

Large business networks that support many thousands of network devices require high density modular switches to achieve the best use of space and energy. Without the use of a high density modular switch, the network would need many fixed configuration switches to include the number of devices that need access to the network. This approach can consume many electrical outlets and a lot of closet space.

Switch Forwarding speeds

Forwarding rates define the processing capabilities of a switch by estimating the amount of data the switch can process per second.
Switch product lines are classified according to forwarding speeds. Basic switches have lower forwarding speeds than business-level switches. It is important to consider forwarding speeds when a switch is selected.

If the speed is too low, it cannot include full cable speed communication through all of its switch ports. Cable speed is the data rate that each Ethernet port can obtain on the switch. Data rates can be 100 Mb / s, 1 Gb / s, 10 Gb / s or 100 Gb / s .

Power over Ethernet

Power over Ethernet ( PoE ) allows a switch to supply power to a device through existing Ethernet wiring. This feature can be used in IP phones and some wireless access points.
PoE provides greater flexibility when installing wireless access points and IP phones, allowing them to be installed anywhere with an Ethernet cable. The network administrator must ensure that PoE features are required, because switches that support PoE are expensive.
The relatively new compact Cisco switches of the Catalyst 2960-C and 3560-C series support passage through PoE. The passage through PoE allows the network administrator to power the PoE devices connected to the switch, as well as to the switch itself, by means of energy obtained from certain ascending switches.

Multilayer Switching

Generally, multilayer switches are implemented in the core and distribution layers of an organization's switched network. Multilayer switches are characterized by the ability to create a routing table , by admitting some routing protocols and by forwarding IP packets at a rate similar to layer 2 forwarding. Multilayer switches usually support specialized hardware, such as circuits Integrated application specific (ASIC). ASICs, together with dedicated software data structures, can simplify the forwarding of IP packets independently of the CPU.
In the field of network technology, there is a tendency towards a purely Layer 3 switched environment. When switches were used in networks, none of them supported routing. Today, almost all switches do. It is likely that all switches will soon incorporate a route processor, since the cost of doing so is less and less in relation to other limitations. Finally, the term "multilayer switch" will be redundant.

Network Scaling : how to grow your Network Expansion

Network Scaling : how to grow your Network Expansion

Network Scalling is a very important concept in network design. A well-designed network controls traffic and limits the size of fault domains. A network design must include an IP addressing strategy, scalable and fast convergence routing protocols, appropriate layer 2 protocols and modular or clustered devices that can be easily updated to increase capacity. (how to grow your Network Expansion)
To support an enterprise network, the network designer must develop a strategy that allows the network to be available and can be scaled easily and efficiently .

Table of Contents

• Design that supports scalability
• Advanced network design requirements
• LAN redundancy
• Increase bandwidth
• Expansion of the access layer
• Adjust routing protocols
• OSPF
• EIGRP

Design that supports Scalability

In a basic network design strategy, the following recommendations are included:

• Use expandable modular equipment or grouped devices that can be easily upgraded to increase capacities. Device modules can be added to existing equipment to support new devices and features without the need for large-scale equipment updates. Some devices can be integrated into a cluster to function as a single device, to simplify administration and configuration.
• Design the hierarchical network to include modules that can be added, updated and modified as necessary, without affecting the design of other functional areas of the network. For example, create a separate access layer that can be expanded without affecting the distribution and core layers of the campus network.
• Create an IPv4 or IPv6 address strategy that is hierarchical . If IPv4 addressing is meticulously planned, the need to redirect the network to support additional users and services is avoided.
• Choose routers or multilayer switches to limit broadcast and filter other unwanted traffic on the network. Use Layer 3 devices to filter and reduce traffic to the network core.

Advanced network design requirements

As shown in Image 1, the most advanced network design requirements include the following:

• The implementation of redundant links in the network , between the essential devices and the access layer and core layer devices.
• The implementation of several links between the teams , either with link aggregation ( EtherChannel ) or with load balancing of the same cost to increase bandwidth. The combination of several Ethernet links in a single configuration with EtherChannel load balancing increases the available bandwidth. EtherChannel implementations can be used when, due to budget constraints, high-speed interfaces or fiber optic lines cannot be acquired.
• The implementation of wireless connectivity to allow mobility and expansion.
• The use of a scalable routing protocol and the implementation of features within that protocol to isolate routing updates and minimize the size of the routing table.

LAN Redundancy

For most organizations, network availability is critical to meet business needs. Redundancy is an important part of network design to prevent interruptions of network services by minimizing the possibility of a single point of failure. One method of implementing redundancy is to install duplicate equipment and provide failover services for essential devices.
Another method of implementing redundancy is through redundant routes. Redundant routes offer alternative physical routes for data to cross the network. In a switched network, redundant routes support high availability. However, due to the operation of the switches, redundant routes in a switched Ethernet network may cause logical loops in layer 2. For this reason, the tree expansion protocol ( STP ) is required.
The STP protocol allows the redundancy necessary to provide reliability, but eliminates switching loops. To do this, it provides a mechanism to disable redundant routes in a switched network until the route becomes necessary, for example, when a fault occurs. It is an open standards protocol, which is used in a switching environment to create a logical topology without loops.
In the next chapter "LAN redundancy", more details about LAN redundancy and STP operation are described.

Increase bandwidth

In the hierarchical network design, some links between access and distribution switches may need to process a greater amount of traffic than other links. As the traffic of several links converges on a single outbound link, a bottleneck may occur in that link .
Link aggregation allows the administrator to increase bandwidth between devices by creating a logical link composed of several physical links. As shown in Image 3, EtherChannel is a form of link aggregation that is used in switched networks.

EtherChannel uses the existing switch ports, therefore it is not necessary to incur additional costs to update the link to a faster and more expensive connection. The EtherChannel link looks like a logical link that uses an EtherChannel interface. Most configuration tasks are performed on the EtherChannel interface instead of on each individual port, which ensures configuration consistency across all links.
Finally, the EtherChannel configuration takes advantage of load balancing between the links that are part of the EtherChannel itself and, depending on the hardware platform, one or more load balancing methods can be implemented.

Expansion of the Access layer

The network should be designed to be able to expand network access for people and devices , as necessary. For the extension of access layer connectivity, wireless connectivity is increasingly important . The provision of wireless connectivity provides many advantages, such as increased flexibility, reduced costs and the ability to grow and adapt to the changing requirements of networks and businesses.

To communicate wirelessly, the terminals require a wireless NIC that incorporates a radio transmitter or receiver and the software driver necessary for it to work. As shown in Image 4, a wireless router or a wireless access point (AP) is also required for users to connect.

Adjust routing protocols

ISPs and business networks generally use more advanced routing protocols, such as link status protocols , due to their hierarchical design and the ability to scale to larger networks.

OSPF

Link state routing protocols, such as the OSPF (Open Shortest Path First) protocol , shown in Image 5, work well in larger hierarchical networks, where it is important to have rapid convergence. OSPF routers establish and maintain neighbor adjacencies with other OSPF routers connected.
When routers initiate an adjacency with neighbors, an exchange of Link-State updates begins . Routers reach a FULL adjacency state by synchronizing the views of their Link-State databases. With OSPF, Link-State updates are sent every time there are changes in the network.
OSPF is a popular link state routing protocol that can be adjusted in many ways. In the chapter “Setting and solving single area OSPF problems”, some of the more advanced features of OSPF configuration and troubleshooting are detailed.

In addition, OSPF supports a two-layer hierarchical design, or multi-area OSPF, shown in figure. All OSPF networks begin with an Area 0, also called a backbone area. As the network expands, other areas that are not backbone can be created. All non-backbone areas must be connected directly to area 0. In the chapter " Multi-area OSPF ", the benefits, operation and configuration of multi-area OSPF are presented.

 EIGRP

Another popular routing protocol in larger networks is the Enhanced Interior Gateway Routing Protocol (EIGRP). Cisco developed EIGRP as an exclusive vector distance routing protocol with enhanced capabilities. Although the EIGRP configuration is relatively simple, this protocol has broad and strong underlying features and options.

For example, EIGRP uses several tables, which are shown in above figure, to manage the routing process. EIGRP contains many functions that none of the other routing protocols have. It is an excellent choice for large multi-protocol networks in which Cisco devices are mainly used.
The "EIGRP" chapter describes the operation and configuration of the EIGRP routing protocol, while the chapter "Advanced configuration and troubleshooting of EIGRP" covers some of the most advanced EIGRP configuration options.

Network Design and Implementation

Network Design and Implementation

Article is on Strategies and methods used to systematically setup Network Design and Implementation, such as the hierarchical network design model and the Cisco enterprise architecture.
As a company grows, its network requirements also increase. Companies rely on network infrastructure to provide essential services. Network interruptions can cause profit and customer losses. Network designers must design and build a business network that is scalable and highly available .
Companies are increasingly turning to their network infrastructure to provide mission-critical services. As companies grow and evolve, they hire more employees, open branches and expand to global markets. These changes directly affect the network requirements. The network used to support the business activities of the company is called the business network .
A business network must support the exchange of various types of network traffic, including data files, email, IP telephony and video applications for various business units.
Table of Contents

1. Commercial Devices for Companies
2. Hierarchical Network Design
3. Cisco Enterprise Architecture
4. Failure domains

Commercial Devices For Companies

Users expect business networks, such as the one shown in Image 2, to be active 99.999% of the time. The interruptions that occur in business networks prevent companies from carrying out their normal activities, which can lead to loss of profits, customers, data and opportunities.

In order to reach this level of reliability, advanced technology equipment of enterprise class is usually installed in the business network. Business teams, designed and manufactured to meet stricter standards than cheaper devices, carry a large volume of network traffic.
High-tech equipment is designed to be reliable, with features such as redundant power supplies and migration capacity in case of failures. Failover capability is the ability of a device to move from a module, service or device that does not work to one that does without interrupting the service or with minimal interruption.

Hierarchical Network Design

To optimize bandwidth in an enterprise network, the network must be organized so that traffic is maintained at the local level and does not spread unnecessarily to other parts of the network. The use of the three-layer hierarchical design model helps to organize the network.

In above figure, in this model the functionality of the network is divided into three different layers.

1. Access layer
2. Distribution layer
3. Core layer

Each layer is designed to fulfill specific functions.
The access layer provides connectivity to users. The distribution layer is used to send traffic from one local network to another. Finally, the core layer represents a high-speed backbone between the dispersed networks. User traffic starts at the access layer and passes through the other layers if you need to use the functionality of those layers.

Although the hierarchical model consists of three layers, a two-tier hierarchical design may be implemented in some small business networks. As shown in Image 4, in a two-tier hierarchical design , the core and distribution layers are combined into one, which reduces cost and complexity.

Cisco Enterprise Architecture

The Cisco enterprise architecture divides the network into functional components , while maintaining the core, distribution and access layers.

As shown in Image 5, the main modules of the Cisco enterprise architecture include the following:

1. Business campus
2. Business perimeter
3. Perimeter of the service provider
4. Remote

 Business campus

The business campus module is composed of all the campus infrastructure and includes the access, distribution and core layers.

• The access layer module includes layer 2 or layer 3 switches to provide the required port density. In this module, the implementation of VLANs and trunk links to the building's distribution layer occurs. Redundancy to building distribution switches is important.
• The distribution layer module adds access to the building through layer 3 devices. In the distribution layer module, routing, access control and QoS are carried out.
• The core layer module provides high-speed inter connectivity between the distribution layer modules, the data center server farms and the business perimeter. In this module, the central axis of the design is redundancy, rapid convergence and fault tolerance.

In addition to these modules, the business campus may include other sub-modules, such as the following:
Data center and server farm module : this area provides high speed connectivity and protection for servers. It is very important to provide security, redundancy and fault tolerance.
Services module : this area provides access to all services, such as IP telephony services, wireless controller services and unified services.

Business perimeter

The business perimeter module is composed of the Internet, VPN and WAN modules that connect the company to the service provider's network. This module extends the company's services to remote sites and allows the company to use Internet and partner resources. Provides QoS, policy reinforcement, service levels and security.

Perimeter of the service provider

The perimeter module of the service provider provides Internet, public switched telephone network (PSTN) and WAN services .
The composite business network (ECNM) model passes through an end device. This is the moment in which the packages can be analyzed and the decision can be made as to whether they should be allowed to enter the business network. Intrusion detection systems (IDS) and intrusion prevention systems (IPS) can also be configured on the business perimeter to provide protection against malicious activities.

Failure domains

A well-designed network not only controls traffic, but also limits the size of fault domains . A fault domain is the area of ​​the network that is affected when an essential device or network service experiences problems.
The function of the device that initially fails determines the impact of the fault domain. For example, a switch that malfunctions in a network segment usually affects only the hosts in that segment. However, if the fault occurs in the router that connects this segment with other segments, the impact is much greater.
The use of redundant links and reliable high-tech equipment minimizes the chances of interruptions to network services. If the domains of failures are smaller, the impact of the failures on the productivity of the company is reduced. In addition, they simplify the problem-solving process, which reduces downtime for all users.

Limitation of fault domain size

Since a failure in the core layer of a network can have a great impact, the network designer often focuses on efforts to prevent failures. These efforts can lead to a large increase in the cost of network implementation. In the hierarchical design model, it is easier and generally more economical to control the size of a fault domain in the distribution layer. In this layer, network errors can be contained in a smaller area, so that fewer users are affected. When layer 3 devices are used in the distribution layer, each router functions as a gateway for a limited number of users in the access layer.

Implementation of a switch block

Routers, or multilayer switches, are generally implemented in pairs, and access layer switches are divided equally between them. This configuration is called " building switch block " or "department". Each block of switches works independently. As a result, the failure of a single device does not deactivate the network. Not even the failure of a whole block of switches affects a large number of end users.

Configure of DHCP server and DHCP Client on Cisco Router

Configure of DHCP server and DHCP Client on Cisco Router

In this section, you will get complete details on Configure of DHCP server and DHCP Client on Cisco Router. Step by step and all the commands you should learn. If you learn about what is DHCP you can visit here.
A Cisco router running Cisco IOS software can be configured to function as a DHCP server . The DHCP server used by Cisco IOS assigns and manages IPv4 addresses from specified address sets within the router for DHCP clients. The topology shown in figure is used to illustrate this functionality.

HOW TO CONFIGURE A DHCP SERVER IN CISCO ROUTER

• Step 1: Exclude IPv4 addresses

The router that functions as a DHCP server assigns all IPv4 addresses in a set of DHCP addresses, unless it is configured to exclude specific addresses. Generally, some IPv4 addresses in a set are assigned to network devices that require static address assignments. Therefore, these IPv4 addresses should not be assigned to other devices. To exclude specific addresses, use the ip dhcp excluded-address command  , as shown below:
R1 (config) # ip dhcp excluded-address  low-address [ high-address ]
A single address or range of addresses can be excluded by specifying the lowest address and the highest address in the range. Excluded addresses must include the addresses assigned to routers, servers, printers and other devices that were configured or will be configured manually.
R1 (config) # ip dhcp excluded-address 192.168.10.1 192.168.10.9
R1 (config) # ip dhcp excluded-address 192.168.10.254

• Step 2: Configure a DHCPv4 pool

The configuration of a DHCP server involves defining a set of addresses to be assigned. As shown below, the ip dhcp pool set-  name command   creates a set with the specified name and places the router in DHCP configuration mode, which is identified with the Router (dhcp-config) # flag.
R1 (config) # ip dhcp pool  pool-name 
R1 (dhcp-config) #
R1 (config) # ip dhcp pool LAN-POOL-1 
R1 (dhcp-config) #

• Step 3: Configure specific tasks

Finally, the tasks to complete the configuration of the DHCP pool are indicated. Some of them are optional, while others must be configured.

REQUIRED AND OPTIONAL TASKS FOR DHCP

Required Tasks

Required Tasks	Command
Define the address set.	network network number [mask | prefix-length]
Define the default router or gateway.	default-router address [address2… address8]
Table of configuration of specific tasks.

Optional Tasks

Optional Tasks	Command
Define a DNS server.	dns-server address [address2… address8]
Define the domain name.	domain-name domain
Define the duration of the DHCP grant.	read {days [hours] [minutes] | infinite}
Define the WINS server with NetBIOS.	netbios-name-server address [address2… address8]
Table of configuration of specific tasks.

Use the default-router command   to define the default gateway router. Normally, the gateway is the LAN interface of the router closest to the client devices. A gateway is required, but up to eight addresses can be indicated if there are several gateways.
Other commands in the DHCP pool are optional. For example, the IPv4 address of the DNS server that is available to a DHCP client is configured using the dns-server command  . The  domain-name  domain command  is used to define the domain name. The lease duration of DHCPv4 can be modified using the lease command  . The default lease value is one day. The netbios-name-server command   is used to define the WINS server with NetBIOS.

DHCP CONFIGURATION EXAMPLE

An example configuration with basic DHCPv4 parameters configured on router R1 is shown below. R1 is configured as a DHCPv4 server for LAN 192.168.10.0/24 using the example topology of Image 1.
R1 (config) # ip dhcp excluded-address 192.168.10.1 192.168.10.9
R1 (config) # ip dhcp excluded-address 192.168.10.254 
R1 (config) # ip dhcp pool LAN-POOL-1
R1 (dhcp-config) # network 192.168.10.0 255.255.255.0
R1 (dhcp-config) # default-router 192.168.10.1
R1 (dhcp-config) # dns-server 192.168.11.5
R1 (dhcp-config) # domain-name example.com
R1 (dhcp-config) # end
R1 #
The DHCP service is enabled by default. To disable the service, use the global configuration mode no service dhcp command  . Use the dhcp  global configuration mode command  to re-enable the DHCP server process. If the parameters are not set, enabling the service has no effect.

DHCP VERIFICATION

In the example result, the topology shown in Image 1 is used. In this example, R1 was configured to provide DHCP services. Since PC1 did not turn on, it does not have an IP address.

SHOW RUNNING-CONFIG COMMAND

As shown below, in the result of the  show running-config | dhcp section , the DHCP commands configured in R1 are displayed. The parameter  | section  shows only the commands associated with the DHCP configuration.
R1 # show running-config | dhcp section
ip dhcp excluded-address 192.168.10.1 192.168.10.9
ip dhcp excluded-address 192.168.10.254
ip dhcp excluded-address 192.168.11.1 192.168.11.9
ip dhcp excluded-address 192.168.11.254
ip dhcp pool LAN-POOL-1
 network 192.168.10.0 255.255.255.0
 default-router 192.168.10.1 
 dns-server 192.168.11.5 
 domain-name example.com
ip dhcp pool LAN-POOL-2
 network 192.168.11.0 255.255.255.0
 default-router 192.168.11.1 
 dns-server 192.168.11.5 
 domain-name example.com
R1 #
SHOW IP DHCP BINDING COMMAND
As shown in the following result, DHCPv4 operation can be verified using the show ip dhcp binding command  . This command shows a list of all the links of the IPv4 address with the MAC address that were provided by the DHCPv4 service.

R1 # show ip dhcp binding Bindings from all pools not associated with VRF: IP address Client-ID / Lease expiration Type Hardware address / User Name
The following command,  show ip dhcp server statistics , is used to verify if the router receives or sends messages. This command displays counting information regarding the number of DHCPv4 messages that were sent and received.R1 # show ip dhcp server statistics

Memory usage 23543
Address pools 1
Database agents 0
Automatic bindings 0
Manual bindings 0
Expired bindings 0
Malformed messages 0
Secure arp entries 0

Message Received
BOOTREQUEST 0
DHCPDISCOVER 0
DHCPREQUEST 0
DHCPDECLINE 0
DHCPRELEASE 0
DHCPINFORM 0

Message Sent
BOOTREPLY 0
DHCPOFFER 0
DHCPACK 0
DHCPNAK 0
R1 #

As seen in the result of these commands, there are currently no links, and statistics indicate that there are no messages sent or received. At this time, no device requested DHCPv4 services from router R1.

SHOW IP DHCP COMMAND

In the following result, the commands are issued after PC1 and PC2 were turned on and the boot process finished.

R1 # show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID / Lease expiration Type
           Hardware address /
           User Name
192.168.10.10 0100.e018.5bdd.35 May 28 2013 01:06 PM Automatic
192.168.11.10 0100.b0d0.d817.e6 May 28 2013 01:10 PM Automatic

R1 # show ip dhcp server statistics
Memory usage 25307
Address pools 2
Database agents 0
Automatic bindings 2
Manual bindings 0
Expired bindings 0
Malformed messages 0
Secure arp entries 0

Message Received
BOOTREQUEST 0
DHCPDISCOVER 8
DHCPREQUEST 3
DHCPDECLINE 0
DHCPRELEASE 0
DHCPINFORM 0

Message Sent
BOOTREPLY 0
DHCPOFFER 3
DHCPACK 3
DHCPNAK 0
R1 #

Note that the information about the bindings now shows that IPv4 addresses 192.168.10.10 through 192.168.11.10 joined the MAC addresses. Statistics also show DHCPDISCOVER, DHCPREQUEST, DHCPOFFER and DHCPACK activity.

IPCONFIG / ALL COMMAND

As shown in Image 2, the ipconfig / all command  , when issued on PC1, shows the TCP / IP parameters. Since PC1 was connected to network segment 192.168.10.0/24, it automatically received a DNS suffix, an IPv4 address, a subnet mask, a default gateway and a DNS server address from that pool. No DHCP specific router interface configuration is required. If a computer is connected to a network segment that has an available DHCPv4 pool, the computer can obtain an IPv4 address from the appropriate pool automatically.

DHCP RELAY

In a complex hierarchical network, business servers are usually located in a server farm. These servers can provide DHCP, DNS, TFTP and FTP services for the network. Generally, network clients are not on the same subnet as those servers. To locate servers and receive services, clients often use broadcast messages.

In figure, PC1 attempts to acquire an IPv4 address from a DHCP server through a broadcast message. In this situation, router R1 is not configured as a DHCPv4 server and does not forward the broadcast message. Since the DHCPv4 server is located on a different network, PC1 cannot receive an IP address via DHCP.

IPCONFIG / RELEASE AND IPCONFIG / RENEW COMMANDS

In Image 4, PC1 tries to renew its IPv4 address. To do this, the ipconfig / release command is issued  . Note that the IPv4 address is released, and the address is shown to be 0.0.0.0. Next, the ipconfig / renew command is issued  . This command causes PC1 to broadcast a DHCPDISCOVER message. The result shows that PC1 cannot locate the DHCPv4 server. Since routers do not forward broadcast messages, the request is not correct.

As a solution to this problem, an administrator can add DHCP servers on all subnets. However, running these services on several computers generates an additional cost and administrative overhead.
A better solution is to configure a Cisco IOS help address. This solution allows the router to forward DHCPv4 broadcasts to the DHCPv4 server. When a router forwards assignment requests / address parameters, it acts as a DHCPv4 relay agent. In the example topology, PC1 would broadcast a request to locate a DHCPv4 server. If R1 was configured as a DHCPv4 relay agent, it would forward the request to the DHCPv4 server located on subnet 192.168.11.0.

IP HELPER-ADDRESS COMMAND

As shown below, the interface on R1 that receives the broadcast is configured with the ip helper-address interface configuration mode command  . The DHCP server address is configured as the only parameter.
R1 (config) # interface g0 / 0
R1 (config-if) # ip helper-address 192.168.11.6
R1 (config-if) # end
R1 # show ip interface g0 / 0
GigabitEthernet0 / 0 is up, line protocol is up 
 Internet address is 192.168.10.1/24
 Broadcast address is 255.255.255.255
 Address determined by setup command
 MTU is 1500 bytes
 Helper address is 192.168.11.6
When R1 is configured as a DHCP relay agent, it accepts broadcast requests for the DHCP service and then forwards those requests as a unicast to IPv4 address 192.168.11.6. The show ip interface command   is used to verify the configuration.
As shown in Image 5, PC1 can now acquire an IPv4 address from the DHCPv4 server.

DHCPv4 is not the only service that can be configured to relay the router. By default, the ip helper-address command   forwards the following eight UDP services:

• Port 37: Time
• Port 49: TACACS
• Port 53: DNS
• Port 67: DHCP / BOOTP client
• Port 68: DHCP / BOOTP server
• Port 69: TFTP
• Port 137: NetBIOS Name Service
• Port 138: NetBIOS datagram service

Configuration of a router as a DHCPv4 client

Occasionally, Cisco routers in small offices and home offices (SOHO) and at branch sites must be configured as DHCPv4 clients similar to client computers. The specific method used depends on the ISP. However, in its simplest configuration, the Ethernet interface is used to connect to a cable modem or a DSL modem. To configure an Ethernet interface as a DHCP client, use the ip address dhcp interface configuration mode command  .

In figure, suppose an ISP was configured to provide IP addresses of the network range 209.165.201.0/27 to select clients. After the G0 / 1 interface is configured with the  ip address dhcp command, the show ip interface g0 / 1 command   confirms that the interface is activated and that the address was assigned by a DHCPv4 server.

SOHO (config) # interface g0 / 1
SOHO (config-if) # ip address dhcp
SOHO (config-if) # no shutdown
SOHO (config-if) #
* Jan 31 17: 31: 11.507:% DHCP-6-ADDRESS_ASSIGN: Interface
GigabitEthernet0 / 1 assigned DHCP address 209.165.201.12, mask
255.255.255.224, hostname SOHO
SOHO (config-if) # end
SOHO # show ip interface g0 / 1
GigabitEthernet0 / 1 is up, line protocol is up
 Internet address is 209.165.201.12/27
 Broadcast address is 255.255.255.255
 Address determined by DHCP

CONFIGURING A WIRELESS ROUTER AS A DHCP CLIENT

Normally, wireless routers for home or small office use are connected to an ISP using a cable modem or DSL. In most cases, wireless routers are configured to receive IPv4 addressing information automatically from the ISP.

For example, the illustration shows the default WAN configuration page for a Packet Tracer wireless router. Note that the type of Internet connection is set to  Automatic Configuration - DHCP  . This selection is used when the router connects to a modem or DSL cable and acts as a DHCP client and requests an IPv4 address from the ISP.