Specifications

Configuring Asynchronous Lines and Interfaces
How to Configure Other Asynchronous Line and Interface Features
DC-29
Cisco IOS Dial Technologies Configuration Guide
You cannot use the auxiliary (AUX) port as a second console port. To use the AUX port as a console port,
you must order a special cable from your technical support personnel.
On an access server, you can configure any of the available asynchronous interfaces (1 through 8, 16, or
48). The auxiliary port (labeled AUX on the back of the product) can also be configured as an
asynchronous serial interface, although performance on the AUX port is much slower than on standard
asynchronous interfaces and the port does not support some features.
Table 4 illustrates why asynchronous interfaces permit substantially better performance than AUX ports
configured as asynchronous interfaces.
On routers without built-in asynchronous interfaces, only the AUX port can be configured as an
asynchronous serial interface. To configure the AUX port as an asynchronous interface, you must also
configure it as an auxiliary line with the line aux 1 command. Access servers do not have this restriction.
Use the line command with the appropriate line configuration commands for modem control, such as
speed.
Only IP packets can be sent across lines configured for SLIP. PPP supports transmission of IP, Internet
Packet Exchange (IPX), and AppleTalk packets on an asynchronous serial interface.
See the “Line AUX Configuration Example” section for an example that shows how to configure the
AUX port.
Establishing and Controlling the EXEC Process
By default, the Cisco IOS software starts an EXEC process on all lines. However, you can control EXEC
processes, as follows:
• Turn the EXEC process on or off. (A serial printer, for example, should not have an EXEC session
started.)
• Set the idle terminal timeout interval.
The EXEC command interpreter waits for a specified amount of time to receive user input. If no input
is detected, the EXEC facility resumes the current connection. If no connections exist, it returns the
terminal to the idle state and disconnects the incoming connection.
Table 4 Differences Between the Asynchronous Port and the Auxiliary (AUX) Port
Feature Asynchronous Interface Auxiliary Port
Maximum speed 115200 bps 38400 bps
DMA buffering support
1
1. Direct Memory Access (DMA) buffering moves data packets directly to and from system memory without
interrupting the main CPU. This process removes overhead from the CPU and increases overall system
performance.
Yes N o
PPP framing on chip
2
2. PPP framing on a hardware chip removes overhead from the CPU on the router, which enables the router to
sustain 115200 bps throughput on all asynchronous ports simultaneously.
Yes N o
IP fast switching
3
3. After the destination of the first IP packet is added to the fast switching cache, it is fast switched to and from
other interfaces with minimal involvement from the main processor.
Yes N o