Net Guide,Cisco Network Guide

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Network Essentials for

Small Businesses:

A Step-by-Step Planning Guide


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It is also possible to mix and match services. For example,small branch offices or individual employees dialing infrom home might connect to your central office usingISDN or DSL, while the main connection from the centraloffice to the Internet would be a T-1.

Which service you select also depends on what your InternetService Provider (ISP) is using. If your ISPs maximum linespeed is 128K, as with ISDN, it wouldnt make sense toconnect to that ISP with a T-1 service. It is important tounderstand that as the bandwidth increases, so do thecharges, both from the ISP and the phone company. Keep inmind that rates for different kinds of connections vary fromlocation to location. See the next chapter for illustrations ofhow various wide area connections might work.

Also consider that a VPN can allow you to extend full pri-vate-network and Internet access to remote offices andindividuals, at a significant savings compared to usingleased lines or long-distance calls for remote connectivity.Ask yourself these additional questions:

Are you adding remote sites or remote users at a rapidpace?

Are your current remote-access line costs rising rapidly?

Would you rather focus on your core business than on

building a WAN?

Do you plan to create an extranet, and offer password-protected access to suppliers, customers or other tradingpartners?

If you answered yes to any or all of these questions, youmay be a good candidate for a VPN. Contact ServiceProviders for details on their VPN offerings.

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As the Office Network Grows

Unfortunately, this network cant accommodate the grow-ing demands of the business. Too many users are compet-ing for the 10 Mbps Ethernet network pathway. Only oneuser can connect to the Internet at one time from a modem.And as employees begin incorporating more graphics intheir files and sending these files back and forth betweentheir clients and the server, network performance stumbles.

The solution is to segment the network using Ethernetswitches and add a router for Internet connections. Thisprovides more bandwidth for all employees and permitsmultiple simultaneous links to the Internet through oneline. The business can give product designers using band-width-hungry computer-aided design (CAD) programs theperformance they need and dedicated 10-Mbps Ethernet

channels to their individual workstations. And the net-work upgrade saves money by incorporating existingequipment and wiring.

Figure 4: Growing LAN

FrameRelay

Router

EthernetSwitch

High Bandwidth Users

To ISP& Internet

Server

Workgroup withEthernet Switch

Workgroup withEthernet Hub

Server

Hub


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A Small-Scale Virtual Private Network (VPN)

A small business is adding remote sites and users at ahectic pace. Connecting them all via leased lines and dial-up access would require the business to devote more timeto administering its wide area network and would meandramatically higher line charges and long-distance phonebills each month. Instead, the company chooses to imple-ment a VPN, with help from its Service Provider. TheService Provider has access points to its network acrossthe nation, so the remote users can connect with theircompanys central network using inexpensive local calls.At the central site, a Cisco 1720 VPN Access Router pro-vides an all-in-one solution for connecting to the ServiceProvider (and the public Internet). It integrates a router,firewall, encryption and tunneling services, password pro-

tection, and a high-speed link to the central sites LAN.

Figure 7: Small-Scale VPN

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IOS Firewall

T1

VPN Tunnels

ISP

IOS Firewall

Internet

VPN Router

Ethernet

Switch

Switch

Access

Server Laptop

VPNRouter

IOS Firewall

Switch

VPNRouter


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Cabling is an additional equipment consideration whendeciding on switched or Fast Ethernet. Switched Ethernetruns on the common two-pair Category 3 cabling thatmany companies have installed as well as Category 4 andCategory 5 UTP (unshielded twisted pair) cabling. But100BaseTX, the most commonly used Fast Ethernet imple-mentation, requires Category 5 cabling. All new UTP cableinstallations should be Category 5.


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For Connecting Offices and Departments

Clients with NICs installed

Servers

Hubs

Switch Cabling

Network Operating System software (e.g., Windows NT,Windows 95, Novell Netware, LANtastic, and AppleShare.)

Router for shared Internet access (optional)

Figure 11: Connecting Offices and Departments

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Router

T1 Line





Floor 1 LAN

Floor 2 LAN

Floor 3 LAN

Internet




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Modem Device that enables a computer toconnect to other computers and net-works using ordinary phone lines.Modems modulate the computersdigital signals into analog signals fortransmission, then demodulatethose analog signals back into digitallanguage that the computer on theother end can understand.

Packet A block of data with a headerattached that can indicate what thepacket contains and where it is head-ed. Think of a packet as a dataenvelope, with the header acting asan address.

Remote Access Device that handles multiple incom-Server ing calls from remote users who needaccess to central network resources.A remote access server can allowusers to dial into a network using asingle phone number. The serverthen finds an open channel andmakes a connection without return-ing a busy signal.

Router Device that moves data between dif-ferent network segments and canlook into a packet header to deter-mine the best path for the packet totravel. Routers can connect networksegments that use different proto-cols. They also allow all users in anetwork to share a single connectionto the Internet or a WAN.

Server A computer or even a software pro-gram that provides services toclientssuch as file storage (fileserver), programs (application serv-er), printer sharing (print server), fax(fax server) or modem sharing(modem server). See also client.

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