Cisco 7206VXR - VPN Bundle Router, Руководство по установке

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Cisco 7206 Installation and Configuration Guide
OL-5102-02
Chapter 2 Preparing for Installation
Site Requirements
•
Strong EMI, especially when it is caused by lightning or radio transmitters, can destroy the signal
drivers and receivers in the Cisco 7206, and can even create an electrical hazard by conducting
power surges through lines and into equipment. (Review the safety warnings in the Site Preparation
and Safety Guide.)
Note
To predict and remedy strong EMI, you may also need to consult experts in radio frequency interference
(RFI).
If you use twisted-pair cable in your plant wiring with a good distribution of grounding conductors, the
plant wiring is unlikely to emit radio interference. If you exceed the recommended distances, use a
high-quality twisted-pair cable with one ground conductor for each data signal when applicable.
If wires exceed recommended distances, or if wires pass between buildings, give special consideration
to the effect of a lightning strike in your vicinity. The electromagnetic pulse caused by lightning or other
high-energy phenomena can easily load enough energy into unshielded conductors to destroy electronic
devices. If you have had problems of this sort in the past, you may want to consult experts in electrical
surge suppression and shielding.
Distance Limitations and Interface Specifications
The size of your networks and the distances between connections depend on the type of signal, the signal
speed, and the transmission media (the type of cabling used to transmit the signals). For example,
standard coaxial cable has a greater channel capacity than twisted-pair cabling. The distance and rate
limits in the following descriptions are the IEEE-recommended maximum speeds and distances for
signaling; however, you can usually get good results at speeds and distances far greater than these. For
example, the recommended maximum rate for V.35 is 2 Mbps, but it is commonly used at 4 Mbps
without any problems. If you understand the electrical problems that might arise and can compensate for
them, you should get good results with rates and distances greater than those shown here; however, do
so at your own risk.
Note
We recommend that you do not exceed specified transmission rate and distance limits.
When preparing your site for network connections to the Cisco 7206, you must consider a number of
factors related to each type of interface:
• The type of cabling required for each type (fiber, thick or thin coaxial, shielded twisted-pair, or
unshielded twisted-pair cabling)
•
Distance limitations for each signal type
• The specific cables you need to connect each interface
• Any additional interface equipment you need, such as transceivers, hubs, switches, modems,
channel service units (CSUs), or data service units (DSUs)
• Cable pinouts if you plan to build your cables
The information listed above is contained in the documentation that is shipped with each port adapter.
For example, if you need ATM distance limitations and pinouts, refer to the configuration note PA-A3
Enhanced ATM Port Adapter Installation and Configuration. This configuration note accompanies each
PA-A3 enhanced ATM port adapter that is shipped from the factory as an installed item in a Cisco 7206
and as a FRU.
Before installing the Cisco 7206, have all additional external equipment and cables on hand. For
ordering information, contact a customer service representative.