If we were to examine the entire line of products that Cisco produced, we could become overwhelmed rather quickly by all the selections. Deciding on the correct product for use today as well as for the future can often be a daunting task. In this section we will examine the types of routers that can be used for remote access and where each of those routers are positioned best.
Central Site Selection
The central site is usually the headquarters but it can also be a primary destination for most remote sites. This site may use multiple WAN types terminated at various remote sites and therefore the router (or routers) must be able to grow with the demand.
The central site must be designed with many of the WAN considerations. Choosing the right WAN type must be based on cost and bandwidth. Keeping the cost low while still maintaining a solid flow of traffic defines the role of the remote access router.
The central site must also maintain security. Since the role of this router is to allow remote access to the corporate LAN, unintentional or unauthorized access must be restricted. This can be accomplished with PPP authentication, AAA servers, VPNs, and access lists.
Finally, if downtime must be kept minimal, then reliability and fault tolerance must be taken into account. There may need to be backup links in the event of a primary link failure, or even a standby router running the Hot Standby Routing Protocol (HSRP).
The Cisco 7000 series routers are high-performance routers that can scale well to future needs. This model has a high port density, which means that many WAN connections can be added to support a large number of remote sites. This port density is accomplished with modular interfaces that can be added as needed. It has the speed to process demanding traffic patterns that a central office might require.
The Cisco AS5000 series routers are a step down from the 7000. One of the best features of this model of router is the integration of routing, switching, channel services (CSU), and modems. Internet Service Providers (ISPs) often use this model of router to provide services to customers.
Stepping down from the AS5000 are the 4000 series routers. This series of routers, including the 4500 and 4700, offer remote access capabilities using two 16-port asynchronous modules for modems. The routers can also offer, instead, two T1/E1 PRI modules.
The final router that can be used for the central site is the 3600 series router. These are also modular routers that support a large array of LAN and WAN interfaces. For example, the 3640 supports four network modules, which can consist of T1 ports, asynchronous ports, digital modems, Ethernet, Token Ring, and many combinations of these interfaces. In fact, more modules are being released to support an ever-growing demand in the WAN connectivity.
Branch Office Selection
Also known as remote sites, these are the sites that connect to the central site for access to the enterprise servers. There are fewer users at these sites than at the central site, but there can be 5, 50, 100, or more users. The number of users can affect the bandwidth requirements and therefore the WAN type. Because of this, choosing the correct router for connection to the central site can be a complicated task. Devices that offer fixed interfaces are cheaper to implement but cannot be upgraded for future demands. Devices with modular interfaces are typically more expensive, but can allow for that future growth.
Designs of the branch office must keep in mind total bandwidth needed, availability of the WAN connection types, security mechanisms to prevent unauthorized access, and possibly even redundancy. Designers must decide if the cost of an "always-on" link is justified, or if a "dial-on-demand" link should be used.
The Cisco 2600 series router is a good candidate for future growth that provides many of the options necessary for different types of LAN and WAN connectivity. This router comes equipped with a single network module slot and two WAN Interface Card (WIC) slots. Most of the modules that work with the 3600 series router will work with the 2600. Each router has either a single LAN connection or dual LAN connections consisting of Ethernet, Fast Ethernet, and/or Token Ring.
The 2500 series router, long considered the staple (and stable!) product, consists of fixed ports with at least one LAN interface and two high-speed serial ports for T1s. There are many different models of this router, available with asynchronous ports, ISDN, hubs, Ethernet, and Token Ring interfaces. While cheaper than the 2600 because of the fixed interfaces, future growth can require a complete replacement.
The 1720 router is a router that is used when VPNs are necessary. Providing support for two WIC slots using some of the same modules available for the 3600/2600, this router is able to use various WAN connectivity types. It also comes with a built-in 10/100 autosensing interface.
The 1600 series routers are a combination of fixed and modular routers. The router contains a single slot for WIC cards. These cards are some of the same used for the 3600/2600/1700 series routers. This provides connectivity using a single WAN type. If another connection is desired at a later date, such as to another remote site as well as the central site, a new router must be purchased.
Telecommuter/Small Office Home Office Selection
This type of site is for a single user or a couple of users at most. Telecommuters, for example, dial in from either home or from hotels. These types of routers are often set up with some type of asynchronous or ISDN connection, although support for other types of WANs do exist. These sites are designed based primarily on cost, both the local cost and the cost of connection to the central site. Also, authentication may be a design issue.
The Cisco 1000 series routers are fixed interface routers that can provide additional WAN types beyond modems and ISDN.
All of the routers that have been discussed so far, and the Cisco 800 series, use the standard Cisco IOS for configuration. The 800 series router is the lowest cost of all the IOS-based routers. Most of these routers provide ISDN service with LAN connections.
The final router that can be used for the Telecommuter/SOHO is the Cisco 700 series router. This is the cheapest router and does not use the Cisco IOS. While saying this is the cheapest router, we must remember the support time needed to learn and maintain a different syntax. This can actually cause the price to be more than the couple hundred dollars difference between this router and the 800 series routers. This router is also an ISDN router and supports multiple protocols, such as TCP/IP and IPX/SPX.
Product Selection Tool
To aid designers in choosing the correct network device, Cisco has released a Product Selection Tool that allows the designer to select the features necessary. Based on that information, the tool will return the product lines that fit those needs.
This product is also available on Cisco's Web site (Figure 1-4). It is a Perl script that imitates the executable that can be found on Cisco's CD-ROMs. Visit http://www.cisco.com/pcgi-bin/front.x/corona/prodtool/select.pl.
Figure 1-4 Finding a Cisco Router product on the Web.