Distance Limitations - Cisco 2600 Series Operation Manual

The synchronous serial port can be configured as DTE or DCE (except EIA-530, which is
DTE only), depending on the attached cable. To order a shielded cable, contact customer
service. (See the Cisco Information Packet publication that came with your router.)
Note
other DCE device.
Although manufacturing your own serial cables is not recommended (because of the small
size of the pins on the DB-60 serial connector), cable pinouts are provided in the online
document Cisco Modular Access Router Cable Specifications. This document is located on
the Documentation CD-ROM that accompanied your router, and on Cisco Connection
Online.

Distance Limitations

Serial signals can travel a limited distance at any given bit rate; generally, the slower the
data rate, the greater the distance. All serial signals are subject to distance limits, beyond
which a signal degrades significantly or is completely lost.
Table 6-2 lists the recommended maximum speeds and distances for each serial interface
type; however, if you understand potential electrical problems and compensate for them,
you may get good results at speeds and distances greater than those listed. For instance, the
recommended maximum rate for V.35 is 2 Mbps, but 4 Mbps is commonly used.
Table 6-2
Rate (bps)
2400
4800
9600
19200
All serial ports configured as DTE require external clocking from a CSU/DSU or
Serial Interace Speeds and Distances
EIA/TIA-232
Distance
Feet Meters
200 60
100 30
50 15
25 7.6
EIA/TIA-449, X.21, V.35, EIA-530
Distance
Feet Meters
4100 1250
2050 625
1025 312
513 156
Connecting Serial Network Modules to a Network 6-3
Distance Limitations