2-11
Hardware Installation Guide for the Cisco 4000 Series  Integrated Services Router
OL-32185-02
Chapter 2      Cisco 4000 Series ISRs Preinstallation
  Power Guidelines and Requirements
Power Guidelines and Requirements
Check the power at your site to ensure that you are receiving “clean” power (free of spikes and noise). 
Install a power conditioner if necessary.
The AC power supply includes the following features:
• Autoselects either 110 V or 220 V operation. 
• All units include a 6-foot (1.8-meter) electrical power cord. (A label near the power inlet indicates 
the correct voltage, frequency [AC-powered systems only], current draw, and power dissipation for 
the unit.)
Table 2-3 lists power requirements for the Cisco  4451-X ISRs.
Network Cabling Specifications
The following sections describe the cables needed to install your Cisco 4000 Series ISRs in the following 
sections:
• Console and Auxiliary Port Considerations, page 2-11
• Prepare for Network Connections, page 2-14
Console and Auxiliary Port Considerations
The router includes an asynchronous serial console port and an auxiliary port. The console and auxiliary 
ports provide access to the router either locally using a console terminal connected to the console port, 
or remotely using a modem connected to the auxiliary port. This section discusses important cabling 
information to consider before connecting the router to a console terminal or modem.
The main difference between the console and auxiliary ports is that the auxiliary port supports hardware 
flow control and the console port does not. Flow control paces the transmission of data between a 
sending device and a receiving device. Flow control ensures that the receiving device can absorb the data 
sent to it before the sending device sends more. When the buffers on the receiving device are full, a 
message is sent to the sending device to suspend transmission until the data in the buffers is processed. 
Because the auxiliary port supports flow control, it is ideally suited for use with the high-speed 
transmissions of a modem. Console terminals send data at speeds slower than modems do; therefore, the 
console port is ideally suited for use with console terminals.
Note Cisco 4221 ISR does not have an auxiliary port.
Table 2-3 Power Requirements for Cisco  4451-X ISRs 
Router Power Source  Input Power Input Voltage 
Tolerance Limits
Cisco  4451-X ISR  AC 100 — 240 VAC, 5.3 A, 50 — 60 Hz 90 — 264 VAC
Cisco  4451-X ISR with 
PoE
AC 100 — 240 VAC, 11.0 A, 50 — 60 Hz 90 — 264 VAC