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So why is the 2500 router one of the 10 most significant products of the past decade? The list is long: It was at the forefront of the Internet buildout. Cisco created a product that was small and affordable at a time when others were offering large enterprise- or carrier-size products. An entry-level 2500 router costs about $2,500 and still satisfies most users' needs. It can be configured to handle a variety of Layer 3 protocols--including IP, IPX, Apple Computer's AppleTalk and Digital Equipment's DECnet--and routing protocols--such as RIP versions 1 and 2, IGRP (Interior Gateway Routing Protocol), EIGRP (Enhanced IGRP) and BGP (Border Gateway Protocol). Finally, Cisco's IOS software makes it easy to configure, and it runs like a tank.

The 2500 evolved from Cisco's original two 2000-series routers; the company introduced the first four models of the 2500 series seven months after the 2000's introduction.

Soon after--though the 2000 series was still alive in some minds--the 2500 became the better known of the two because of its durability and superior features--and in November 1997, it passed the 1 million mark in terms of units sold. Over the years, 16 more variations have been added to the 2500 series product line, and today--with the 2000 series long gone from Cisco's product list--the company continues to enhance its 2500 series.

The first four 2500 models improved on the 2000 series by providing a second asynchronous port, an option for an ISDN BRI connection, flash memory and unbundled software. The addition of a second asynchronous port meant the 2500 could now maintain more than one active connection simultaneously, while the BRI port enabled routing over ISDN lines, which meant offices within the same metropolitan area were no longer limited to slower, less stable analog connections. Connections through both the second asynchronous port and the BRI port also could be used for redundant links to frame relay clouds or private networks if the primary connection failed, thus providing near 100 percent uptime for critical data applications.

The addition of flash memory created a product that was code- and feature-upgradable long after leaving the assembly line. Although the Cisco 2500 held only one software image in flash memory at a time, software upgrades could still be performed quickly and easily. No longer was the internal operating software locked into a chip that would need to be replaced for upgrade; Cisco customers could now load whatever software they wanted, whenever they wanted, either locally or remotely.

Finally, in unbundling its application software from its hardware, Cisco gave customers a choice of three levels of software, each differing in functionality and protocol-routing choices. If a customer needed only simple IP routing, for example, that customer could choose the lowest-level IP router software and thus avoid paying extra for unneeded features or protocols.

The entire 2500 line consists of fixed hardware configurations, requiring customers to purchase the configuration that best suits their needs. A couple of years ago, however, Cisco improved on the 2500 even further with the introduction of the 2600 router line--an upgrade that retains the same internal components but adds swappable interface modules, letting customers create the router of their choice.