Wide Area Network Scenario
This lab focuses "out-of-band" router management using the
AUX port on the router and a modem. You can configure and
monitor routers and other networking equipment using both in-band
and out-of-band techniques. For example, let's say Router Lab-A is
in Anaheim, CA. and Lab-B is in Boise, ID. They are connected via a
wide area link such as T1 Frame Relay, PRI ISDN or Point-to-Point
over T1. Regardless of which you use , your WAN link has a the
bandwidth or "speed" of a T1 (1.544 Mbps). You are a
Network Administrator in Anaheim and wish to make some configuration
changes or check the status for the Lan-B router in Boise.
In-Band Network Management
If you are attached to the console of router Lab-A and telnet to
Router Lab-B across the wide area link, your connection to router
Lab-B is considered in-bandwidth or "in-band" since you
are using the same WAN link that the data travels on to manage the
Lab-B router. If the WAN link goes down or there is a problem with
the configuration of the Lab-B router that contributes to the down
WAN link, you cannot get to the Lab-B router to monitor or change
its configuration since the WAN link is down. In-band management is
very common and is preferred if the WAN link is up.
Out-of Band Network Management
If the Wan link is down you need a "back-door" or an
"out-of-band" method to get to the router and check it out
to help troubleshoot the problem. This can be provided by redundant
Synchronous WAN serial links to other interfaces on the router. They
can be the same as the existing high speed WAN link or can be slower
such as BRI ISDN or a perhaps a synchronous 56kbps digital data
circuit. You can also get to the router by use of its Asynchronous serial ports. Most routers have 2
Asynchronous ports in order to
manage the router "out-of-band"; the Console port and the
AUX or Auxiliary port.
The use of the Asynchronous console port or the AUX port is
considered "out-of-band" management.
The Console port vs. The AUX port
The primary method of configuring routers with these labs has been
with the console port. With the console port, your workstation is
directly attached to the router with a special rollover cable and
bypasses any other interfaces on the router. The console port is
normally set to run at 9600 bps (8 data bits, no parity and 2 stop
bits or 8-N-2) and does not support hardware flow control. The AUX
port requires a modem be attached and allows you to dial into the
router from home or any other location. The AUX port can run at the
same speed as the fastest modems up to 56kbps and supports hardware
flow control. The Console and AUX ports normally use RS-232 serial
DB25 connectors (converted to RJ45).
Synchronous vs Asynchronous Serial Interfaces
Nearly all Wide Area Network links (WAN) links used in
Internetworking are "serial" meaning they transmit bits
one after another in a series down the wire or fiber cable. They are
not the same as the Asynchronous serial connection ports found on
the back of most PCs and those used with modems. The console
connection from a workstation to the console port on the router is
an Asynchronous connection which uses start and stop bits to
separate the data bits in the stream. The bit rate on the Asynchronous
router console port is set to 9600 bits per second
(bps). Asynchronous serial connections are commonly used with short
distance connections for terminals (to routers and switches) or for
dial-in modem connections which are limited to 56kbps (Kilobits per
second or 56 thousand bits per second). A modem can be connected to
the AUX port on the router to allow you to dial in Asynchronously
and diagnose problems. With this lab you will practice setting up a
modem with the router and dialing in from another location to
configure it remotely. Note that the AUX port can also be use for
Dial-on Demand routing in case the main WAN serial link is down.
- Configure the line Asynchronous data transmission parameters to 8
data bits, No Parity and 2 Stop bits (8, None and 2 or 8-N-2)
- Enter the following command to set the number of data bits to 8
Router(config-line)# databits 8
- Enter the following command to set the parity to None
Router(config-line)# parity none
Enter the following command to set the number of data bits to 8
Router(config-line)# stopbits 2
- Check the configuration of the AUX port with the show running-config
command. The output from the command should show the following port
characteristics:
- line aux 0
- password cisco
- login
- autohangup
- flowcontrol hardware
- Copy the running configuration to the startup configuration to save
the AUX port configuration commands you have entered.
Router# copy run start
- Plug the rollover cable RJ45 connector into the AUX port on the back of
the router
Step 2 - Prepare the Workstation used for
Dial-in
- Review the workstation's 'HyperTerminal' configuration.
Click on Start, Programs, Accessories, and then HyperTerminal. Right
Click on the icon that is defined for AUX access to the Cisco Router
and then click Properties. If one does not exist you can create it
using the settings shown in the answers to the worksheet. On the
Properties screen, click the Phone Number Tab and then click the on
the Configure button. Fill in the following table with the information
indicated.
- Configure the workstation modem (internal or external) to match the
transmission settings (speed, Data bits, Parity, Stop bits and Flow
Control) for the router AUX port. Fill in the following table with the
settings and values you used:
Configuration Option |
Current Setting(s) |
COM Port |
Modem Driver Name |
Bits per second
(baud) |
34800 |
Data bits |
8 |
Parity bits |
None |
Stop bits |
2 |
Flow control |
Hardware |
Step 3 - Dial-in to the router
Using the phone number of the line to the router or a modem
eliminator (null modem) cable connected to the router. You should get a
prompt and be able to configure it remotely.
Step 4 - Use ConfigMaker to create a dial-in Asynchronous
WAN link
Start ConfigMaker and select a Cisco 2501 router. Select a Dial-in
PC with Modem for dial-in and add an Async link between them.
Double click on the router to see the configuration generated.