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Table of Contents

Configuring the Software

Configuring the Software

This chapter briefly describes procedures for configuring the router, and contains the following sections:

This chapter provides minimum software configuration information; it is not intended as complete router configuration instructions. Detailed software configuration information is available in the Cisco IOS configuration guide and command reference publications. These publications are available on the documentation CD that accompanied your order or you can order printed copies.

Booting the Router for the First Time

Each time you power on the router, it goes through the following boot sequence:


  1. The router goes through power-on self-test diagnostics to verify basic operation of the CPU, memory, and interfaces.

  2. The system bootstrap software executes and searches for a valid Cisco IOS image (router operating system software). The source of the Cisco IOS image (Flash memory or a Trivial File Transfer Protocol [TFTP] server) is determined by the configuration register setting. The factory-default setting for the configuration register is 0x2102, which indicates that the router should attempt to load a Cisco IOS image from Flash memory.

  3. If after five attempts a valid Cisco IOS image is not found in Flash memory, the router reverts to boot ROM mode (which is used to install or upgrade a Cisco IOS image).

  4. If a valid Cisco IOS image is found, then the router searches for a valid configuration file.

  5. If a valid configuration file is not found in NVRAM, the router runs the System Configuration Dialog so you can configure it manually. For normal router operation, there must be a valid Cisco IOS image in Flash memory and a configuration file in NVRAM.

The first time you boot your router, you will need to configure the router interfaces and then save the configuration to a file in NVRAM. See the section "Configuring the Router for the First Time" or refer to the configuration note for the appropriate module for interface configuration information. See the section "Saving Configuration Changes" later in this chapter for information on how to save the router configuration to NVRAM.

Passwords

Because many privileged-level EXEC commands are used to set operating parameters, you should password-protect access to privileged mode to prevent unauthorized use.

You can set two passwords to do this:

The enable password and enable secret password must be different. In both cases, a number cannot be the first character. Spaces are also valid password characters; for example, "two words" is a valid password. Leading spaces are ignored; trailing spaces are recognized.

For information about setting passwords, refer to the Cisco IOS configuration guides and command references. You can also set these passwords using the setup facility. See the section "Using the System Configuration Dialog" later in this chapter.

If you lose or forget your enable password, see the section "Recovering a Lost Enable Password" in the appendix "Troubleshooting." The enable secret password is encrypted, and cannot be recovered; you must replace it with a new enable secret password.

Configuring the Router for the First Time

You can configure the router using one of the following procedures, which are described in this section:

Proceed with the procedure that best fits the needs of your network configuration and Cisco IOS software experience level.

Time Saver Acquire the correct network addresses from your system administrator or consult your network plan to determine the correct addresses before you begin to configure the router.

If you will be using configuration mode or AutoInstall to configure the router, and you would like a quick review of the Cisco IOS software, refer to the section "Cisco IOS Software Basics" later in this chapter.

Using the System Configuration Dialog

If you do not plan to use AutoInstall, make sure all the WAN cables are disconnected from the router. The router will attempt 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 Transmission Control Protocol/Internet Protocol (TCP/IP) host.

If your router does not have a configuration (setup) file and you are not using AutoInstall, the router will automatically start the setup command facility. An interactive dialog called the System Configuration Dialog appears on the console screen. This dialog helps you navigate through the configuration process by prompting you for the configuration information necessary for the router to operate.

Many prompts in the System Configuration Dialog include default answers, which are included in square brackets following the question. To accept a default answer, press Return; otherwise, enter your response.

This section gives an example configuration using the System Configuration Dialog. When you are configuring your router, respond as appropriate for your network.

At any time during the System Configuration Dialog, you can request help by typing a question mark (?) at a prompt.

Before proceeding with the System Configuration Dialog, obtain from your system administrator the node addresses and the number of bits in the subnet field (if applicable) of the router ports. For more information about IP addresses and subnets, refer to the Internetworking Technology Overview publication.

Note You can run the System Configuration Dialog any time you are at the privileged EXEC prompt (#) by entering the setup command.

Take the following steps to configure the router using the System Configuration Dialog:

Step 1 Connect a console terminal to the console port on the front panel of your router, and then power ON the router. (For more information, refer to the section "Connecting the Console Terminal and Modem" in the chapter "Installing the Router.")

Step 2 After about 30 seconds, information similar to the following is displayed on the console screen:

Step 3 Press Return or enter yes to begin the configuration process.

Step 4 When the System Configuration Dialog asks whether you want to view the current interface summary, press Return or enter yes:

Step 5 Configure the global parameters. A typical configuration follows:

Next, you are prompted to enter an enable secret password. There are two types of privileged-level passwords:


The enable password is used when the enable secret password does not exist.


For maximum security, be sure the passwords are different. If you enter the same password for both, the router will accept your entry, but will display a warning message indicating that you should enter a different password.


Step 6 Enter an enable secret password:

Step 7 Enter the enable and virtual terminal passwords:

Step 8 Press Return to accept Simple Network Management Protocol (SNMP) management, or enter no to refuse it:

Step 9 In the following example, the router is configured for AppleTalk, Internet Protocol (IP), and Internetwork Packet Exchange (IPX). Configure the appropriate protocols for your router:

Step 10 If your router includes an ISDN BRI port, enter the ISDN BRI switch type. The switch type appropriate for the router depends on the ISDN service provider's equipment. Table 4-1 lists the ISDN switch types.

Country ISDN Switch Type Description
Australia basic-ts013 Australian TS013 switches
Europe basic-1tr6 German 1TR6 ISDN switches
basic-nwnet3 Norwegian NET3 ISDN switches (phase 1)
basic-net3 NET3 ISDN switches (UK and others)
Europe basic-net5 NET5 switches (UK and Europe)
vn2 French VN2 ISDN switches
vn3 French VN3 ISDN switches
Japan ntt Japanese NTT ISDN switches
New Zealand basic-nznet3 New Zealand NET3 switches
North America basic-5ess AT&T basic rate switches
basic-dms100 NT DMS-100 basic rate switches
basic-ni1 National ISDN-1 switches

Configuring the ISDN BRI Interface

This section describes how to configure the ISDN BRI interface. If your router does not include an ISDN BRI interface, proceed to the next section, "Configuring Ethernet Interfaces."

The ISDN BRI interface is configured to allow connection to ISDN WANs. Determine which protocols to support on the ISDN BRI interface and enter the appropriate responses. In the following example, the system is being configured for IP, AppleTalk, and IPX:

Configuring interface BRI0/0:
Is this interface in use? [yes]
Configure IP on this interface? [yes]
IP address for this interface: 172.16.71.1
Number of bits in subnet field [0]: 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? [no]: yes
    AppleTalk starting cable range [0]: 1
    AppleTalk ending cable range [1]: 2
    AppleTalk zone name [myzone]:
    AppleTalk additional zone name: otherzone
    AppleTalk additional zone name:
  Configure IPX on this interface? [no]: yes
    IPX network number [1]: B000

Configuring Ethernet Interfaces

The Ethernet interfaces are configured to allow connection to a LAN. To configure the interface parameters, you need to know the Ethernet interface network addresses.

Take the following steps to configure an Ethernet interface to allow communication over a LAN:

Step 1 Press Return or enter yes to configure the LAN interface:

Step 2 Determine which protocols you want to support on the LAN interface and enter the appropriate responses. In the following example, the system is being configured for IP, AppleTalk, and IPX:

Step 3 If there is more than one LAN interface on your router, repeat this procedure to configure the second and subsequent LAN interfaces.

Configuring Fast Ethernet Interfaces

The Fast Ethernet interfaces are configured to allow connection to a LAN. To configure the interface parameters, you need to know the Fast Ethernet interface network addresses.

Take the following steps to configure an Ethernet interface to allow communication over a LAN:

Step 1 Press Return or enter yes to configure the LAN interface:

Step 2 Determine which protocols you want on the LAN 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:

Step 3 If there is more than one LAN interface on your router, repeat this procedure to configure the second and subsequent LAN interfaces.

Configuring Token Ring Interfaces

The Token Ring interfaces are configured to allow connection to a LAN. To configure the interface parameters, you need to know the Token Ring interface network addresses.

Take the following steps to configure a Token Ring interface to allow communication over a LAN:

Step 1 Press Return or enter yes to configure the LAN interface:

Step 2 Determine which protocols you want to support on the LAN interface and enter the appropriate responses. In the following example, the system is being configured for IP, AppleTalk, and IPX:

Step 3 If there is more than one LAN interface on your router, repeat this procedure to configure the second and subsequent LAN interfaces.

Configuring Serial Interface

The serial interfaces are configured to allow connection to WANs through a CSU/DSU. All serial ports are initially configured as synchronous ports. After the initial configuration is completed, configure the serial ports you plan to use as asynchronous ports using the physical-layer command in configuration mode.

Take the following steps to configure the serial port(s):

Step 1 Press Return or enter yes to configure serial port 0 in slot 0:

Step 2 Determine which protocols you want on the synchronous serial interface and enter the appropriate responses. In the following example, the system is being configured for IP, AppleTalk, and IPX:

Step 3 If there is more than one serial interface on your router, repeat this procedure to configure the remaining serial interfaces.

Step 4 The configuration you entered is now displayed and you are asked if you want to use the displayed configuration. If you enter no, you will lose the configuration information you just entered and you can begin the configuration again. If you enter yes, the configuration will be entered and saved in the startup configuration:

If you have asynchronous serial, T1, or E1 interfaces installed in your router, proceed to the section "Additional Startup Configuration Tasks."

Refer to the section "Cisco IOS Software Basics" for more information about the Cisco IOS software.

Configuring a Switched 56 Interface

To configure a switched 56 interface, you must use configuration mode (manual configuration). In this mode, you can enter Cisco Internetwork Operating System (Cisco IOS) commands at the router prompt.

Before you begin to configure a switched 56 interface, 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.

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

Choosing Circuit-Switched or Dedicated Line Service

The switched 56 WAN interface card is configured for dedicated or leased-line service by default, but you can also configure it for circuit-switched service.

Generally, circuit-switched service is suited for short-duration data transmissions or as an alternative route if a dedicated line fails. For example, circuit-switched service is ideal for sending electronic mail messages or updating inventory and order records from one network database to another at the end of each day. To configure the card for circuit-switched service, continue with the next section, "Configuring Circuit-Switched Service."

Dedicated service is suited for heavy network traffic. Dedicated service is ideal if you need a constant network connection or if you need connection for more than eight hours per day. To configure the card for dedicated service, continue with the section "Configuring Dedicated Line Service" later in this document.

Configuring Circuit-Switched Service

Follow these steps to configure the switched 56 WAN interface card for circuit-switched service, substituting the addresses and host names for your network:

Step 1 Enter enable mode:

Step 2 Enter configuration mode:

Step 3 Assign an IP address to the serial port on the WAN interface card:

Step 4 Set the network type to "switched":

Step 5 Set the carrier type, where carrier can be att, sprint, or other:

Step 6 Enter dialer information:

Step 7 Return to user EXEC mode:

Configuring Dedicated Line Service

Follow these steps to configure the switched 56 WAN interface card for dedicated or leased-line service, substituting the addresses and host names for your network:

Step 1 Enter enable mode:

Step 2 Enter configuration mode:

Step 3 Assign an IP address to the serial port on the WAN interface card:

Step 4 Set the network type to Digital Data System (DDS) for dedicated or leased-line service:

Step 5 Return to user EXEC mode:

Refer to the section "Cisco IOS Software Basics" later in this chapter for more information about Cisco IOS software.

Additional Startup Configuration Tasks

When you have completed the setup facility, you might need to complete some additional configuration tasks. Complete the following tasks that apply to your installation:

Setting Asynchronous Serial Ports

The ports you plan to use as asynchronous serial ports must be reconfigurated after the initital setup. The following steps provide an example of how to configure a synchronous serial port to be an asynchronous serial port.

Step 1 Enter the command config terminal to enter configuration mode:

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


Step 2 Select the serial interface to configure:

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


Step 3 Because all serial ports are initially configured as synchronous, you must change the port to asynchronous operation by entering the physical-layer command:

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


Step 4 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 115200 bps, you would enter the following commands:


To return an asynchronous port to synchronous operation, use the configuration mode physical-layer sync command.


Step 5 If you have completed the configuration, press Ctrl-Z to exit configuration mode.

Step 6 Write the new configuration to memory, as follows:

The system displays a confirmation message when the configuration is saved.


Step 7 Enter the disable command to return to the user level:

Step 8 Enter the show commands to check the configuration of the interface.

For information on using the show commands, see the section "Network Statistics" later in this chapter.


This completes the procedure to configure a synchronous serial interface for asynchronous operation.

Setting Synchronous Serial Ports

Use this procedure if it is necessary to set a serial port previously configured for asynchronous operation back to synchronous operation.

Take the following steps to configure a low-speed asynchronous serial port to be a low-speed synchronous serial port:

Step 1 Enter the config terminal command at the privileged EXEC prompt to enter configuration mode:

Step 2 Enter the interface command to select the port you are configuring:

Step 3 Enter the physical-layer command to set the port to synchronous:

Step 4 When you have completed the configuration, press Ctrl-Z to exit configuration mode.

Step 5 Write the new configuration to memory, as follows:

The system displays a confirmation message when the configuration is saved.


Step 6 Enter the disable command to return to the user level:

Step 7 Enter the show commands to check the configuration of the interface.

This completes the procedure to configure an asynchronous serial interface for synchronous operation.

Setting Half-Duplex Mode

Low-speed serial ports that are set as DCE can be set to use either controlled carrier mode or constant carrier mode.

Controlled carrier mode sets the interface to deactivate data carrier detect (DCD) until a transmission is sent to the interface. DCD is then activated, and the interface waits an amount of time you configure, and then transmits the data. After the transmission, the interface waits for a period of time and then deactivates DCD.

Constant carrier mode (the default for low-speed interfaces) activates DCD at all times.

Take the following steps to enable controlled carrier mode:

Step 1 Enter the config terminal command at the privileged EXEC prompt to enter configuration mode:

Step 2 Enter the half-duplex command to reset the port from constant carrier mode to controlled carrier mode:

Step 3 Enter the no half-duplex command to return to constant carrier mode:

Step 4 Enter the half-duplex timer command to specify the time that the interface delays when in controlled carrier mode. For example, to configure the DCD drop delay, enter the following commands, using appropriate values for your system:

The amount of time is specified in milliseconds.


Step 5 Enter the timer command to tailor the delay times for the router ports. Table 4-1 lists the timer commands and their default settings.


Table  4-1: Half-Duplex Timer Commands
Timer Syntax Default Setting (Milliseconds)
CTS1 delay 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 transmit-delay 0

1 CTS = Clear to send.
2 RTS = Ready to send.

Step 6 When you have completed the configuration, press Ctrl-Z to exit configuration mode.

Step 7 Write the new configuration to memory, as follows:

The system displays a confirmation message when the configuration is saved.


Step 8 Enter the disable command to return to the user level:

Step 9 Enter the show commands to check the configuration of the interface.

This completes the procedure to set half-duplex mode in a serial interface.

Setting Serial Ports for DCE/DTE and NRZ/NRZI Operation

All serial interfaces support DTE and DCE modes, and nonreturn to zero (NRZ) and nonreturn to zero inverted (NRZI) formats.

Step 1 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:

Acceptable clock rate settings are as follows:


300
1200
2400
4800
9600
14400
19200
28800 		32000
38400
56000
57600
64000
72000
115200
128000

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 2 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:

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


Step 3 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:

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


Step 4 All serial interfaces support both NRZ and 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:

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


Step 5 If you have completed the configuration, press Ctrl-Z to exit configuration mode.

Step 6 Write the new configuration to memory, as follows:

The system displays a confirmation message when the configuration is saved.


Step 7 Enter the disable command to return to the user level:

Step 8 Enter the show commands to check the configuration of the interface.

This completes the procedure to configure a serial interface for DTE/DCE and NRZ/NRZI operation.

Configuring T1 Interfaces

If your router includes a CT1/PRI (or CT1/PRI-CSU) module, you must enter configuration mode to configure the interfaces.

This procedure can also be used to change the configuration of an existing CT1/PRI module or to configure a CT1/PRI module newly installed in an existing system. If you replaced a CT1/PRI module that was previously configured, the system will recognize the new module and bring it up with the existing configuration.

Use the privileged-level configure command to configure the new module. Have the following information ready when you begin your configuration:

Take the following steps to complete a basic T1 configuration:

Step 1 At the privileged EXEC prompt, enter the configure terminal command to enter configuration mode and specify that the console terminal will be the source of the configuration commands:

Step 2 Enter the controller t1 command to specify the slot number and unit number of the module you are configuring. For more information on slot and unit numbers, refer to the sections "Slot Numbering" and "Unit Numbering" in the chapter "Overview." For example, if you are configuring a T1 interface in slot 1 and that is unit 0, enter the following command:

Step 3 Specify the clock source for the module. The clock source command determines which end of the circuit provides the clocking:

Step 4 Specify the framing type:

Step 5 Specify the line code format:

Step 6 Specify the channel group and time slots to be mapped. The command shown sets the channel group to 0 and time slots 1, 3 through 5, and 7 are selected for mapping.

Step 7 Specify the serial interface, unit number, and channel group you want to modify:

Step 8 Assign an IP address and subnet mask to the interface using the ip address command as follows, substituting the appropriate IP address and subnet mask for your site:

Step 9 Add any additional configuration commands required to enable routing protocols and adjust the interface characteristics. Refer to the Cisco IOS configuration guides and command references for more information on configuration subcommands.

Step 10 When you have completed the configuration, press Ctrl-Z to exit configuration mode.

Step 11 Write the new configuration to memory, as follows:

The system displays a confirmation message when the configuration is saved.


Step 12 Enter the disable command to return to the user level:

Step 13 Enter the show commands to check the configuration of the interface.

This completes the procedure to configure a CT1/PRI interface.

Configuring E1 Interfaces

If your router includes a CE1/PRI module (balanced or unbalanced), you must enter configuration mode to configure the interface.

This procedure can also be used to change the configuration of an existing CE1/PRI module or to configure a CE1/PRI module newly installed in an existing system. If you replaced a CE1/PRI module that was previously configured, the system will recognize the new module and bring it up with the existing configuration.

When you have verified that the new CE1/PRI module is recognized by the router, use the privileged-level configure command to configure the new CE1/PRI module. Have the following information ready when you begin your configuration:

Take the following steps to complete a basic E1 configuration.

Step 1 At the privileged EXEC prompt, enter the configure terminal command to enter configuration mode and specify that the console terminal will be the source of the configuration commands:

Step 2 Enter the controller e1 command to specify the slot and unit number of the E1 interface you are configuring. For more information on slot and unit numbers, refer to the sections "Slot Numbering" and "Unit Numbering" in the chapter "Overview." For example, if you are configuring an E1 interface that is in slot 1 and that is unit 0, enter the following command:

Step 3 Specify the framing type:

Step 4 Specify the channel group and time slots to be mapped. The command shown below sets the channel group to 0 and time slots 1, 3 through 5, and 7 are selected for mapping:

Step 5 Specify the serial interface, unit number, and channel group you want to modify:

Step 6 Assign an IP address and subnet mask to the interface using the ip address command as follows, substituting the appropriate IP address and subnet mask for your site:

Step 7 Add any additional configuration subcommands required to enable routing protocols and adjust the interface characteristics. Refer to the Cisco IOS configuration guides and command references for more information on configuration subcommands.

Step 8 When you have completed the configuration, press Ctrl-Z to exit configuration mode.

Step 9 Write the new configuration to memory, as follows:

The system displays a confirmation message when the configuration is saved.


Step 10 Enter the disable command to return to the user level:

Step 11 Enter the show commands to check the configuration of the interface.

This completes the procedure to configure a CE1/PRI interface.

Increasing the I/O Memory

System configurations with multiple ISDN PRI interfaces or 12 or more ISDN BRI interfaces require more I/O memory than the default.

Cisco 3600 series routers ship with a 75/25 processor/I/O memory split. If your router has 2 ISDN PRI interfaces or more than 12 ISDN BRI interfaces, you must change the memory split to 60/40. The following sections provide information about reallocating processor and I/O memory and provide examples of the memory-size iomem command. Note that if you do not reallocate memory, you will get an error code.

Reallocating Processor Memory and I/O Memory

DRAM memory in Cisco 3600 series routers is organized as one continuous address space divided between processor memory and I/O memory. Depending on the type and number of network interfaces you have configured in the router, you may need to reallocate the DRAM memory partitioned to processor memory and I/O memory.

Cisco manufacturing configures most Cisco 3600 series routers to have 25 percent of the address space allocated to I/O memory and 75 percent allocated to processor memory. But for customers who use two or more ISDN PRI interfaces, DRAM memory must be configured to provide 40 percent of the address space for I/O memory and 60 percent for processor memory. See Figure 4-1.


Figure 4-1: Components and Uses of DRAM Memory for Cisco 3600 Series Routers



After you receive your router, you may have to manually reallocate the DRAM memory split between processor memory and I/O memory.

The following example uses a Cisco 3640 router with the following running configuration:

Later on, however, you add a 4-port ISDN BRI network module to the router. You now have a total of 12 ISDN BRI interfaces running on the router. At this point, you must use the memory-size iomem command to configure 40 percent of the address space for I/O memory and 60 percent for processor memory.

To view your current mix of processor and I/O memory and reassign memory distribution accordingly, enter the following commands beginning in privileged EXEC mode:

Task Command
Step 1 View the total amount of memory loaded on the router. show version
Step 2 Determine the amount of free memory. show memory1
Step 3 Enter global configuration mode. configure terminal
Step 4 Allocate processor memory and I/O memory. memory-size iomem I/O-memory-percentage2
Step 5 Exit global configuration mode. Ctrl-Z
Step 6 Write the new configuration to NVRAM. copy running-config startup-config
Step 7 Reload the router to run the new image. reload

1 The Free(b) column in the show memory command's output shows how much I/O memory is available.
2 The default is 40 percent for I/O memory and 60 percent for processor memory.

Valid I/O memory percentage values are 25, 30, 40 (the default), and 50. I/O memory size is the specified percentage of total memory size, rounded down to the nearest multiple of 1 MB. The remaining memory is processor memory.

The memory-size iomem command is not effective until you save it to NVRAM using the copy running-config startup-config EXEC command and reload the router. However, when you enter the command, the software checks whether the new memory distribution leaves enough processor memory for the currently running Cisco IOS image. If not, the following message appears:

Warning: Attempting a memory partition that does not provide enough Processor memory for the current image.If you write memory now, this version of software may not be able to run.

When you enter the reload command to run a new image, the software calculates the new processor and I/O memory split. If there is not enough processor memory, it automatically reduces I/O memory to an alternative setting to load the image. If there is still not enough processor memory for the image to run, then you do not have enough DRAM.

See the next section for an example of how to configure the memory-size iomem command.

Examples

The percentage of DRAM allocated to I/O memory and processor memory is configurable.

The following example allocates 40 percent of DRAM to I/O memory and the remaining 60 percent to processor memory:

Step 1 From EXEC mode, enter the show memory command to see whether you need to allocate different percentages of processor and I/O memory. The Free(b) column shows how much I/O memory is available:

Step 2 Enter global configuration mode and configure the memory-size iomem command.

Step 3 Write the new configuration to NVRAM:

Step 4 Enter the reload command to run the new image and boot the router from ROM monitor mode:

Note For further information about the memory-size iomem command, refer to the Cisco IOS configuration guides and command references.

Other Configuration Options

Instead of using the system configuration dialog to configure your router, you can use either of the following methods:

Follow the procedure that best fits the needs of your network configuration. If you would like a quick review of Cisco IOS software commands, refer to the section "Cisco IOS Software Basics" later in this chapter.

Time Saver Obtain network addresses from your system administrator or your network plan before you begin router configuration.

Configuring the Router Using Configuration Mode

When you install a new module or WAN interface card, or if you want to change the configuration of an existing interface, you must enter configuration mode to configure the interfaces. If you replace a module or card that was already configured, the router recognizes it and brings up the interfaces in the existing configuration.

Before you configure an interface, have the following information available:

Take the following steps to configure the router manually:

Step 1 Connect a console by following the instructions in the section "Console Port" in the chapter "Installing the Router," and power ON the router.

Step 2 When asked if you would like to enter the initial dialog, answer no:

You now enter the normal operating mode of the router.


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

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


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

You can now enter changes to the configuration, one command per line. For information about configuration commands, refer to the Cisco IOS configuration guides and command references.


Step 5 When you have completed the configuration, press Ctrl-Z to exit configuration mode.

To see the current operating configuration, including any changes you just made, enter the show running-config command at the privileged EXEC prompt:

Router# show running-config

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

Router# show startup-config

The results of the show running-config and show startup-config commands differ from each other if you have made changes to the configuration and have not yet written them to NVRAM.

To write your changes to NVRAM, making them permanent, enter the copy running-config startup-config command at the privileged EXEC prompt:

Router# copy running-config startup-config
Building configuration. . .
[OK]
Router#

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

Configuring the Router Using AutoInstall

The AutoInstall process is designed to configure the router automatically after connection to your WAN. In order for AutoInstall to work properly, a TCP/IP host on your network must be configured to provide the required configuration files.

The TCP/IP host can reside anywhere on the network as long as the following two conditions are satisfied:


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

  2. 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 site where the TCP/IP host is located. You should not attempt to use AutoInstall unless the required files have been installed on the TCP/IP host.

Take the following steps to prepare your router for the AutoInstall process:

Step 1 Attach the appropriate WAN cable to the router.

Step 2 Power ON 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 may want to write the configuration data to the router's NVRAM. To do this, enter the copy running-config startup-config command at the # prompt:

This step saves the configuration settings that the AutoInstall process created. If you fail to do this, the new configuration will be lost the next time you reload the router.


Cisco IOS Software Basics

This section provides you with some basic information about the Cisco IOS software and includes the following sections:

Cisco IOS Modes of Operation

Cisco IOS software provides access to several different command modes. Each command mode provides a different group of related commands.

For security purposes, Cisco IOS software provides two levels of access to commands: user and privileged. The unprivileged user mode is called user EXEC mode. The privileged mode is called privileged EXEC mode and requires a password. The commands available in user EXEC mode are a subset of the commands available in privileged EXEC mode.

Table 4-3 describes some of the most commonly used modes, how to enter the modes, and the resulting prompts. The prompt helps you identify which mode you are in and, therefore, which commands are available to you.

Mode of Operation Usage How to Enter the Mode Prompt
User EXEC User EXEC commands allow you to connect to remote devices, change terminal settings on a temporary basis, perform basic tests, and list system information. The EXEC commands available at the user level are a subset of those available at the privileged level. Log in. Router>
Privileged EXEC Privileged EXEC commands set operating parameters. The privileged command set includes those commands contained in user EXEC mode, and also the configure command through which you can access the remaining command modes. Privileged EXEC mode also includes high-level testing commands, such as debug. From user EXEC mode, enter the enable EXEC command.

Router#
Global configuration Global configuration commands apply to features that affect the system as a whole. From global configuration mode, enter the configure privileged EXEC command. Router(config)#
Interface configuration Interface configuration commands modify the operation of an interface such as an Ethernet, Token Ring, or serial port. Many features are enabled on a per-interface basis. Interface configuration commands always follow an interface global configuration command, which defines the interface type. From global configuration mode, enter the interface type number command. For example, enter the interface serial 0 command to configure the serial 0 interface. Router(config-if)#
ROM monitor ROM monitor commands are used to perform low-level diagnostics. You can also use the ROM monitor commands to recover from a system failure and stop the boot process in a specific operating environment.1 From privileged EXEC mode, enter the reload EXEC command. Press Break during the first 60 seconds while the system is booting. rommon>

1 You can modify the configuration register value using the config-reg configuration command. Refer to the appendix "ROM Monitor" for more information.

Almost every configuration command also has a no form. In general, use the no form to disable a feature or function. Use the command without the keyword no to reenable a disabled feature or to enable a feature that is disabled by default. For example, IP routing is enabled by default. To disable IP routing, enter the no ip routing command and enter ip routing to reenable it. The Cisco IOS software command reference publication provides the complete syntax for the configuration commands and describes what the no form of a command does.

Getting Context-Sensitive Help

In any command mode, you can get a list of available commands by entering a question mark (?).

Router> ?

To obtain a list of commands that begin with a particular character sequence, enter those characters followed immediately by the question mark (?). Do not include a space. This form of help is called word help, because it completes a word for you. 

Router# co?
configure  connect  copy

To list keywords or arguments, enter a question mark in place of a keyword or argument. Include a space before the question mark. This form of help is called command syntax help, because it reminds you which keywords or arguments are applicable based on the command, keywords, and arguments you have already entered. 

Router# configure ?
  memory    Configure from NV memory
  network   Configure from a TFTP network host
  terminal  Configure from the terminal
  <cr>

You can also abbreviate commands and keywords by entering just enough characters to make the command unique from other commands. For example, you can abbreviate the show command to sh.

Saving Configuration Changes

Any time you make changes to the router configuration, you must save the changes to memory because if you do not, they will be lost if there is a system reload or power outage. There are two types of configuration files: the running (currently operating) configuration and the startup configuration. The running configuration is stored in RAM; the startup configuration is stored in NVRAM.

To display the current running configuration, enter the show running-config command. Enter the copy running-config startup-config command to save the current running configuration to the startup configuration file in NVRAM.

Router> enable
Router# copy running-config startup-config

To display the startup configuration, enter the show startup-config command. Enter the copy startup-config running-config command to write the startup configuration to the running configuration:

Router> enable
Router# copy startup-config running-config

To erase both configuration files (and start over), enter the write erase and reload commands:

Router> enable
Router# write erase
Router# reload
Caution This command sequence will erase the entire router configuration in RAM and NVRAM and reload the router.

Checking and Saving Your Settings

To check the settings you have configured, enter the show running-config command at the enable (#) prompt:

Router# show running-config

To store the configuration, enter the copy running-config startup-config command at the enable (#) prompt:

Hostname# copy running-config startup-config

This command saves the configuration settings that the setup process created. If you fail to do this, your new configuration will be lost the next time you reload the router.

Network Statistics

When you have finished configuring the network interfaces, use the show interface command to check network interface statistics. Options to the show interface command include the following:

The following example shows the output of the show interface serial 0/0 command:

Router> show interface serial 0/0
Serial0/0 is administratively down, line protocol is down
  Hardware is QUICC Serial
  Internet address is 172.16.74.1/24
  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
  Encapsulation HDLC, loopback not set, keepalive set (10 sec)
  Last input never, output never, output hang never
  Last clearing of "show interface" counters never
  Input queshowue: 0/75/0 (size/max/drops); Total output drops: 0
  Output queue: 0/64/0 (size/threshold/drops)
     Conversations  0/0 (active/max active)
     Reserved Conversations 0/0 (allocated/max allocated)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     0 packets output, 0 bytes, 0 underruns
     0 output errors, 0 collisions, 16 interface resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions

To display the current internal status of a module, use the show controller command with the interface number options. The following example shows the output of the show controller serial 0/1 command:

Router> show controller serial 0/1
Interface Serial0/1
Hardware is Quicc 68360
idb at 0x60879DA8, driver data structure at 0x6087E140
SCC Registers:
General [GSMR]=0x2:0x00380000, Protocol-specific [PSMR]=0x0
Events [SCCE]=0x0000, Mask [SCCM]=0x0000, Status [SCCS]=0x0000
Transmit on Demand [TODR]=0x0, Data Sync [DSR]=0x7E7E
Interrupt Registers:
Config [CICR]=0x00C9CF00, Pending [CIPR]=0x00000000
Mask   [CIMR]=0xA0000000, In-srv  [CISR]=0x00000000
SDMA Registers:
[SDSR]=0x00000000, [SDAR]=0x00010428, [SDCR]=0x00000772
Command register [CR]=0x640
Port A [PADIR]=0x0130, [PAPAR]=0xFFFF
       [PAODR]=0x0000, [PADAT]=0xD8FF
Port B [PBDIR]=0x0011FF, [PBPAR]=0x00100E
       [PBODR]=0x000000, [PBDAT]=0x00FF7C
Port C [PCDIR]=0x0000, [PCPAR]=0x020E
       [PCSO]=0x0030,  [PCDAT]=0x0DFF, [PCINT]=0x0001
Receive Ring
        rmd(3C010020): status 9000 length 600 address C84E44
        rmd(3C010028): status 9000 length 600 address C85484
        rmd(3C010030): status 9000 length 600 address C85AC4
        rmd(3C010038): status 9000 length 600 address C86104
        rmd(3C010040): status 9000 length 600 address C86744
        rmd(3C010048): status 9000 length 600 address C86D84
        rmd(3C010050): status 9000 length 600 address C873C4
        rmd(3C010058): status 9000 length 600 address C87A04
        rmd(3C010060): status 9000 length 600 address C88044
        rmd(3C010068): status 9000 length 600 address C88684
        rmd(3C010070): status 9000 length 600 address C88CC4
        rmd(3C010078): status 9000 length 600 address C89304
        rmd(3C010080): status 9000 length 600 address C89944
        rmd(3C010088): status 9000 length 600 address C89F84
        rmd(3C010090): status 9000 length 600 address C8A5C4
        rmd(3C010098): status B000 length 600 address C8AC04
Transmit Ring
        tmd(3C0100A0): status 0 length 0 address 0
        tmd(3C0100A8): status 0 length 0 address 0
        tmd(3C0100B0): status 0 length 0 address 0
        tmd(3C0100B8): status 0 length 0 address 0
        tmd(3C0100C0): status 0 length 0 address 0
        tmd(3C0100C8): status 0 length 0 address 0
        tmd(3C0100D0): status 0 length 0 address 0
        tmd(3C0100D8): status 0 length 0 address 0
        tmd(3C0100E0): status 0 length 0 address 0
        tmd(3C0100E8): status 0 length 0 address 0
        tmd(3C0100F0): status 0 length 0 address 0
        tmd(3C0100F8): status 0 length 0 address 0
        tmd(3C010100): status 0 length 0 address 0
        tmd(3C010108): status 0 length 0 address 0
        tmd(3C010110): status 0 length 0 address 0
        tmd(3C010118): status 2000 length 0 address 0
No serial cable attached
SCC GENERAL PARAMETER RAM (at 0x3C010C00)
Rx BD Base [RBASE]=0x20, Fn Code [RFCR]=0x18
Tx BD Base [TBASE]=0xA0, Fn Code [TFCR]=0x18
Max Rx Buff Len [MRBLR]=1536
Rx State [RSTATE]=0x0, BD Ptr [RBPTR]=0x20
Tx State [TSTATE]=0x4000, BD Ptr [TBPTR]=0xA0
SCC HDLC PARAMETER RAM (at 0x3C010C38)
CRC Preset [C_PRES]=0xFFFF, Mask [C_MASK]=0xF0B8
Errors: CRC [CRCEC]=0, Aborts [ABTSC]=0, Discards [DISFC]=0
Nonmatch Addr Cntr [NMARC]=0
Retry Count [RETRC]=0
Max Frame Length [MFLR]=1524
Rx Int Threshold [RFTHR]=1, Frame Cnt [RFCNT]=1
User-defined Address 0000/0000/0000/0000
User-defined Address Mask 0x0000
buffer size 1524
QUICC SCC specific errors:
0 input aborts on receiving flag sequence
0 throttles, 0 enables
0 overruns
0 transmitter underruns
0 transmitter CTS losts
Router>

Note that in this example, the cable type is shown as no cable. If a cable is attached to the port, the cable type is shown, as in the following example:

buffer size 2108  Universal Serial: DTE V.24 (RS-232) cable

If the cable is DCE, the output of the show controller command displays the clock rate. For complete command descriptions and instructions, refer to the Cisco IOS configuration guides and command references.

If You Need More Information

If you need more information, refer to the publications that shipped with the router:

The router runs Cisco IOS software. The Cisco IOS configuration guides and command references are available in the following forms:


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