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Choosing WAN Equipment 51
Inbound calls to an AS5800 router can be digital from another ISDN device or analog from a
dial-up user. Therefore, this router is a good choice for central site dial-up facilities. In a mixed
technology environment with multiple WAN technologies, this router probably isn't the best
choice, but for dial-up deployments, it's hard to beat.
7200 Router Series
This family of routers has been around for a while and represents a wide install base. These
devices provide high-power core LAN/WAN routing capabilities as well as voice integration
capabilities. ATM, ISDN, and circuit emulation services are just a few of the available options
supported.
If an AS5800 solution is being put in place, this router is absolutely necessary. It provides the
router shelf function for the AS5800. Without the 7200, the AS5800 does not function.
The 7200 has a six-slot chassis. The port modules can be mixed and matched for varying
degrees of connectivity and bandwidth. The newer VXR version of the 7200 includes a TDM
bus, which provides better performance than its predecessors. This router is a great choice for
the central site, based on its flexibility and overall power.
Branch Office Router Selection
Branch office sites are the source of many debates when the time comes to connect them to the
central site through a WAN implementation. The amount of bandwidth necessary to adequately
support the site is a crucial factor in the decision-making process. The technology implemented
to provide the necessary bandwidth is equally important.
Consider a small branch office of three users with low bandwidth needs. ISDN BRI might be a
good fit for the installation. However, what if the office grows to 20 users in a short time? At
that point, the 128 kbps can be inadequate to support them, and ISDN BRI has no additional
bandwidth to offer.
If the bandwidth becomes inadequate, a technology and/or router change becomes necessary.
However, the time and costs involved may not be feasible at the current time. Would adequate
planning and an alternate choice of technology have prevented the issue? Yes, they may have
prevented the issue, if there were any indication that this particular office was going to grow as
it did. Overall, it's sometimes a guessing game.
This section of the chapter focuses on some router families that meet the needs of the small- to
medium-sized branch office. These are the 1600, 1700, 2500, and 2600 series routers. Note that
the 3620 can also be a good choice for the branch office, when flexibility is needed. However,
it was discussed in the previous section and need not be revisited.