4-Port and 8-Port Asynchronous/Synchronous Serial Network Module Configuration Note

You can configure the new interfaces and other router parameters by using any of the following methods:

• Configuration Mode (manual configuration)---Recommended if you are familiar with Cisco Internetwork Operating System (Cisco IOS) commands. Enter the commands at the prompt.
  

• AutoInstall---Recommended for automatic installation if another router running Cisco IOS software is installed on the network. This configuration method must be set up by someone with experience using Cisco IOS software.
  

• System Configuration Dialog (setup facility)---Recommended if you are not familiar with Cisco IOS commands. You are prompted for each response.
  

These procedures are explained in the following sections. If you have questions or need help, refer to the section "Obtaining Service and Support" later in this document for further information.

Configuration Mode

You can configure the serial interfaces on your A/S serial network module manually, by entering Cisco IOS commands on the command line. This method, called configuration mode, provides the greatest power and flexibility.

Before you begin, disconnect all WAN cables from the router to keep it from trying to run the AutoInstall process. The router tries to run AutoInstall whenever you power it ON if there is a WAN connection on both ends and the router does not have a valid configuration file stored in nonvolatile random-access memory (NVRAM) (for instance, when you add a new interface). It can take several minutes for the router to determine that AutoInstall is not connected to a remote Transmission Control Protocol/Internet Protocol (TCP/IP) host.

To enter configuration mode, follow this procedure:

Step 1 Connect a console to the router. If you need instructions for connecting a console, refer to the installation chapter of your router installation and configuration guide. Power up the router.

Step 2 If the current configuration is no longer valid, after about a minute you see the following prompt:

Would you like to enter the initial dialog? [yes]:

Answer no. You now enter the normal operating mode of the router.

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If the current configuration is valid, you enter the normal operating mode automatically.

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Step 3 After a few seconds you see the user EXEC prompt (Router>). Type enable and the password to enter enable mode:

Router> enable

Password:

Configuration changes can be made only in enable mode. The prompt changes to the privileged EXEC (enable) prompt (Router#):

Router#

Step 4 Enter the command config terminal to enter configuration mode:

Router# config terminal

Router(config)#

The router enters global configuration mode, indicated by the Router(config)# prompt.

Step 5 If you have not configured the router before, or want to change the configuration, configure global parameters, passwords, network management, and routing protocols. In this example, IP routing, AppleTalk routing, and Internetwork Packet Exchange (IPX) routing are all enabled:

Router(config)# ip routing

Router(config)# appletalk routing

Router(config)# ipx routing

For complete information about global configuration commands, refer to the Cisco IOS configuration guides and command references.

Step 6 Select the serial interface to configure:

Router(config)# interface serial 0/0

Router(config-if)#

The prompt changes again to show that you are in interface configuration mode.

Step 7 Configure routing protocols on the interface. (You must have previously enabled these protocols as part of global configuration.) In this example, IP, AppleTalk, and IPX are being configured on the serial interface:

Router(config-if)# ip address 172.16.74.1 255.255.255.0

Router(config-if)# appletalk static cable-range 5-5

Router(config-if)# appletalk zone ZZSerial

Router(config-if)# ipx network B003

Step 8 All serial ports are initially configured as synchronous. If you want to change the port to asynchronous operation, enter the physical-layer command:

Router(config-if)# physical-layer async

Configure other asynchronous parameters according to your needs, for example:

Router(config-if)# async mode dedicated

Router(config-if)# async default routing

To configure asynchronous line settings, use the line async command. A serial port's line number is related to its slot number and unit number in the following way:

line-number = (16 x slot-number) + unit-number + 1

For example, serial port 1/2 corresponds to line number (16 x 1) + 2 + 1 = 19. To set this port to a speed of 115,200 bps, you would enter the following commands:

line async 19

speed 115200

To return an asynchronous port to synchronous operation, enter the following command:

Router(config-if)# physical-layer sync

Step 9 Low-speed serial ports configured as DCE can be set to use either controlled carrier mode or constant carrier mode. Controlled carrier mode raises DCD only when data is received. The interface waits for a specified period before transmitting; it then waits for another specified period before dropping DCD. Constant carrier mode (the default for low-speed serial interfaces) raises DCD at all times.

To reset the port from constant carrier mode to controlled carrier mode, enter the half-duplex command:

Router(config-if)# half-duplex controlled carrier

To return to constant carrier mode, enter the no half-duplex command:

Router(config-if)# no half-duplex controlled carrier

Step 10 Enter half-duplex timer commands to specify the time that the interface waits in controlled carrier mode. These commands are listed in Table 11. Time is measured in milliseconds. For example, to configure the Data Carrier Detect (DCD) drop delay to 100 ms, enter the following command:

Router(config-if)# half-duplex timer dcd-drop-delay 100

Table 11 : Half-Duplex Timer Commands

Timer	Syntax	Default Setting (Milliseconds)
CTS delay1	half-duplex timer cts-delay	100
CTS drop timeout	half-duplex timer cts-drop-timeout	5000
DCD drop delay	half-duplex timer dcd-drop-delay	100
DCD transmission start delay	half-duplex timer dcd-txstart-delay	100
RTS2 drop delay	half-duplex timer rts-drop-delay	100
RTS timeout	half-duplex timer rts-timeout	2000
Transmit delay	half-duplex timer transmit-delay	0

¹ CTS = Clear To Send.
² RTS = Ready To Send.

Step 11 All serial interfaces support both DTE and DCE modes. To use a port as a DTE interface, connect a DTE serial cable to the port. When the router detects the cable, it automatically uses the external timing signal. To use a port in DCE mode, connect a DCE serial cable and set the internal transmit clock signal (TXC) speed in bits per second with the clockrate command, for example:

Router(config-if)# clockrate 72000

Acceptable clock rate settings are:

1200 2400 4800 9600 19200 38400 56000 64000 72000

125000 148000 500000 800000 1000000 1300000 2000000 4000000

Speeds above 64 kbps (64000) are not supported for EIA/TIA-232.

Use the no clockrate command to remove the clock rate for DTE operation.

Step 12 When a port is operating in DCE mode, the default operation is for the DCE to send serial clock transmit (SCT) and serial clock receive (SCR) clock signals to the DTE, and for the DTE to return a serial clock transmit external (SCTE) signal to the DCE. If the DTE does not return SCTE, you must use the dce-terminal-timing-enable command to configure the DCE port to use its own clock signal:

Router(config-if)# dce-terminal-timing-enable

To disable this command, use the no dce-terminal-timing-enable command.

Step 13 Routers that use long cables may experience high error rates when operating at higher transmission speeds, because the clock and data signals can shift out of phase. If a DCE port is reporting a high number of error packets, inverting the clock using the invert-txc command can often correct this shift:

Router(config-if)# invert-txc

Use the no invert-txc command to change the clock signal back to its original phase.

Step 14 All serial interfaces support both nonreturn to zero (NRZ) and nonreturn to zero inverted (NRZI) formats. NRZ is the default; NRZI is commonly used with EIA/TIA-232 connections in IBM environments. To enable NRZI encoding on an interface, enter the nrzi-encoding command:

Router(config-if)# nrzi-encoding

To disable NRZI encoding on a port, enter the no nrzi-encoding command.

Step 15 To configure another serial interface, enter the exit command to return to the Router(config)# prompt. Repeat Step 6 through Step 14 of this procedure to configure the next serial interface.

Step 16 When you are finished configuring interfaces, exit configuration mode and return to the enable prompt by pressing Ctrl-Z. To see the current operating configuration, including any changes you just made, enter the show running-config command:

Router# show running-config

To see the configuration currently stored in NVRAM, enter the command show startup-config at the enable prompt.

Router# show startup-config

Step 17 The results of the show running-config and show startup-config commands differ from each other if you have made changes to the configuration, but have not yet written them to NVRAM. To write your changes to NVRAM, making them permanent, enter the command copy running-config startup-config at the enable prompt:

Router# copy running-config startup-config

Building configuration. . .

[OK]

Router#

The router is now configured to boot in the new configuration.

AutoInstall

The AutoInstall process is designed to configure the router automatically after it connects to your WAN. For AutoInstall to work properly, a TCP/IP host on your network must be configured to provide the configuration files. The TCP/IP host can reside anywhere on the network if the following two conditions are met:

• The host must be on the remote side of the router's synchronous serial connection to the WAN.
  

• User Datagram Protocol (UDP) broadcasts to and from the router and the TCP/IP host must be enabled.
  

This functionality is coordinated by your system administrator at the TCP/IP host site. You should not try to use AutoInstall unless the required files have been installed on the TCP/IP host.

Follow this procedure to prepare your router for the AutoInstall process:

Step 1 Connect the router to the WAN, following the instructions in the section "Connecting the A/S Serial Module to the Network" earlier in this document.

Step 2 Turn ON power to the router.

The router loads the operating system image from Flash memory. If the remote end of the WAN connection is connected and properly configured, the AutoInstall process begins.

Step 3 If AutoInstall succeeds, you should write the configuration data to the router's NVRAM. To do this, enter the copy running-config startup-config command at the Router# prompt:

Router# copy running-config startup-config

Building configuration. . .

[OK]

Router#

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This step saves the configuration settings that the AutoInstall process created. If you do not do this, your new configuration will be lost the next time you boot the router.

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System Configuration Dialog

You can configure the router manually using the System Configuration Dialog facility. Unlike configuration mode, the System Configuration Dialog prompts you for each response.

Before you begin, disconnect all WAN cables from the router to keep it from trying to run the AutoInstall process. The router tries to run AutoInstall whenever you power it ON if there is a WAN connection on both ends and the router does not have a configuration file stored in NVRAM. It can take several minutes for the router to determine that AutoInstall is not connected to a remote TCP/IP host.

This section shows a sample configuration using the System Configuration Dialog. You should enter values appropriate for your router and network.

Many prompts in the System Configuration Dialog include default answers, shown in square brackets following the question. Enter your response, or press Return to accept the default answer.

You can request help at any time by entering a question mark (?) at a System Configuration Dialog prompt.

Follow this procedure to configure the router using the System Configuration Dialog:

Step 1 Connect a console to the router. If you need instructions for connecting a console, refer to your router installation and configuration guide. Power up the router.

Step 2 If the current configuration is no longer valid, after about a minute you see the following prompt:

Would you like to enter the initial dialog? [yes]:

Press Return or enter yes to enter the System Configuration Dialog.

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You can enter the System Configuration Dialog at any time from the enable prompt (Router#) by entering the setup command.

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Step 3 When the System Configuration Dialog asks whether you want to view the current interface summary, press Return or enter yes:

First, would you like to see the current interface summary? [yes]:

Any interface listed with OK? value "NO" does not have a valid configuration

Interface IP-Address OK? Method Status Protocol

Serial0/0 unassigned NO unset down down

Serial0/1 unassigned NO unset down down

Serial0/2 unassigned NO unset down down

Serial0/3 unassigned NO unset down down

Step 4 If you have not configured the router before, or want to change the configuration, you should now configure global parameters, passwords, network management, and routing protocols. Refer to the procedures in the Cisco IOS configuration guides and command references. Press Return if you want to accept the default values.

Step 5 The System Configuration Dialog prompts you to configure network interfaces. When you reach the first serial interface, determine which protocols you want on the interface and enter the appropriate responses. (You must have previously enabled these protocols as part of global configuration.) In the following example, the interface is being configured for IP, AppleTalk, and IPX:

Configuring interface Serial0/0:

Is this interface in use? [yes]:

Configure IP on this interface? [yes]:

Configure IP unnumbered on this interface? [no]:

IP address for this interface: 172.16.74.1

Number of bits in subnet field [8]:

Class B network is 172.16.0.0, 8 subnet bits; mask is
255.255.255.0

Configure AppleTalk on this interface? [no]: yes

Extended AppleTalk network? [yes]:

AppleTalk starting cable range [2]: 5

AppleTalk ending cable range [3]: 5

AppleTalk zone name [myzone]: ZZSerial

AppleTalk additional zone name:

Configure IPX on this interface? [no]: yes

IPX network number [2]: B003

Step 6 Repeat Step 5 for the remaining serial interfaces.

Step 7 The configuration you entered is displayed as a command script and you are asked if you want to use it. If you enter no, the information you just entered is discarded and you can begin the configuration again. If you enter yes, the configuration is saved in the startup configuration:

Use this configuration? [yes/no]: yes

Building configuration...

Use the enabled mode 'configure' command to modify this configuration.

Press RETURN to get started!

The configuration is saved. If you added an interface, the router reboots in the new configuration when you press Return.

All serial ports are initially configured as synchronous. You can configure serial ports you plan to use as asynchronous or make other changes to the configuration in configuration mode, explained in the section "Configuration Mode" earlier in this document.

Obtaining Service and Support

For service and support for a product purchased from a reseller, contact the reseller. Resellers offer a wide variety of Cisco service and support programs, which are described in the section "Service and Support" in the information packet that shipped with your chassis.