Installation guide

4-66 Cisco 4000 Series Installation Guide
Network Connection Considerations
• Plant cabling can emit radio frequency interference (RFI) if it is unshielded for a
distance exceeding those recommended by the standard.
• Strong electromagnetic interference, especially as caused by lightning or radio
transmitters, can destroy the EIA/TIA-232 drivers and receivers in a router.
If you use twisted-pair cables in your plant wiring with a good distribution of grounding
conductors, the plant wiring is unlikely to emit radio interference. Ground the conductor
for each data signal when exceeding the distances listed in Table 4-5.
If you have cables exceeding the distances in Table 4-5, or if you have cables that pass
between buildings, then give special consideration to the effect of lightning strikes and
ground loops. The electromagnetic pulse caused by lightning and other high-energy
phenomena can couple enough energy into unshielded conductors to destroy electronic
devices; the potential existence of ground loops are also a threat to electrical components
and to safety. If your site has experienced these problems, then consult experts in lightning
suppression and shielding.
Most data centers cannot resolve the infrequent but potentially catastrophic problems just
described without pulse meters and other special equipment. Take precautions to avoid
these problems by providing a properly grounded and shielded environment, with special
attention to issues of electrical surge suppression. To predict and remedy strong
electromagnetic interference, consult experts in RFI.
Configuring Serial Connections
The four-port serial network processor module ports are DB-60 connectors; the dual serial
network processor module ports are DB-50 connectors. (See Figure 4-19 and Figure 4-21.)
These serial ports can be configured as DTE or DCE, depending on the special serial cable
used.
Figure 4-19 shows port numbering on the four-port serial module.