Cisco 1700 series User manual

CHAPTER
Configuring a Leased Line 4-1
4
Configuring a Leased Line
The configuration in this chapter describes how to configure a Cisco 1700 router for IP and IPX over
a synchronous serial line.
Before You Begin
The configuration in this chapter is based on the following assumptions:
•Your Cisco 1700 router hardware is correctly installed according to the Cisco 1700 Router
Hardware Installation Guide that came with the router.
•Your Cisco 1700 router is using multilink Point-to-Point Protocol (PPP).
•Your Cisco 1700 router is using dynamic IP and IPX routing, in which IP Routing Information
Protocol (RIP) resolves IP routes, and IPX RIP and IPX SAP dynamically resolve IPX routes and
services.
Before you begin configuration, be aware of the following:
•You need to enter the commands in the order shown in the task tables.
•The values shown in italic are examples. You should substitute the values shown with values that
are appropriate for your network.
•You should be familiar with Cisco IOS software and its conventions.
Note To use the verification steps described in this chapter, you must be familiar with Cisco IOS
commands and command modes. When you use the verification steps, you need to change to
different commandmodes. If you are not familiar with command modes, refer to the “Understanding
Command Modes” section in the “Cisco IOS Basic Skills” chapter.
These are the major tasks when configuring the router:
•Configuring Global Parameters
•Configuring Security
•Configuring the Fast Ethernet Interface
•Configuring the Serial Interface
•Configuring Dynamic Routing Parameters
•Configuring Command-Line Access to the Router

Configuring Global Parameters
Cisco 1700 Router Software Configuration Guide
4-2
Table 4-1 illustrates the example configuration used in this chapter.
Figure 4-1 Leased Line Example Configuration
Configuring Global Parameters
Use this table to configure the router for some global parameters.
Step Task Router Prompt Command
1Enter configuration mode. Router# configure terminal
2Configure the router to show the date and time of all
debug messages.
This command is optional, but recommended if you use
debug commands to troubleshoot your configuration.
Router(config)# service timestamps debug datetime msec
3Configure the router to show the date and time of all
log messages.
This command is optional, but recommended if you use
the verification steps described in this guide. This
feature is enabled for all the example command output
shown in this guide.
Router(config)# service timestamps log datetime msec
4Configure the router to use subnet zero for interface
addresses and routing updates. Router(config)# ip subnet-zero
5Disable the IP Domain Name System (DNS)-based
host name-to-address translation on the router. Router(config)# no ip domain-lookup
6Enable IPX routing and configure the router with an
IPX address. Router(config)# ipx routing 0000.0caa.1111
Cisco
1700 Cisco 1700
Leased line
IPX network: AAAA
Network address:
IP:10.0.0.0
IPX:100
Network address:
IP:20.0.0.0
IPX:200
Remote site Central site
Ethernet interface
IP address:
10.1.1.1
14486

Configuring a Leased Line 4-3
Configuring Security
Configuring Security
Use this table to configure the router with some security measures.
Configuring the Fast Ethernet Interface
Use this table to configure the Fast Ethernet interface, which connects your router to the local
network.
Configuring the Serial Interface
Use this table to configure the serial interface, which connects your router to the central-site router.
Step Task Router Prompt Command
1Specify a password to prevent unauthorized access to the router. Router(config)# enable password <1700user>
2Configure the router with a host name, which is used in prompts
and default configuration file names.
For PPP authentication, the host name entered with this
command must match the username of the central-site router.
Router(config)# hostname 1700
Step Task Router Prompt Command
1Enter configuration mode for the Fast Ethernet interface. 1700(config)# interface fastethernet0
2Configure this interface with an IP address and a subnet mask.
This interface must have an IP address assigned in order for the
serial interface to be configured for IP unnumbered routing.
1700(config-if)# ip address 10.1.1.1 255.0.0.0
3Enable IPX routing on this interface, assign the IPX network
number, and configure the interface for IPX SAP encapsulation. 1700(config-if)# ipx network 100 encapsulation sap
4Configure a secondary IPX network on this interface that uses
the default NetWare encapsulation. 1700(config-if)# ipx network 100 encapsulation novell-ether secondary
5Enable the interface and the configuration changes you have just
made on the interface. 1700(config-if)# no shutdown
6Exit configuration mode for this interface. 1700(config-if)# exit
Step Task Router Prompt Command
1Enter configuration mode for the serial interface. 1700(config)# interface serial0
2Add a description of this interface to help you remember what is
attached to it. 1700(config-if)# description leased line to headquarters
3Enable IP routing on this interface without assigning an IP
address. 1700(config-if)# ip unnumbered FastEth0
4Enable IPX routing on this interface and assign an IPX network
number. 1700(config-if)# ipx network AAAA

Configuring Dynamic Routing Parameters
Cisco 1700 Router Software Configuration Guide
4-4
Configuring Dynamic Routing Parameters
Use this table to configure some dynamic routing parameters.
Configuring Command-Line Access to the Router
Use this table to configure some parameters that control access to the router.
Verifying Your Configuration
You can verify your configuration by checking the serial interface configuration:
Step 1 From privileged EXEC command mode, enter the show interface serial 0 command.
Step 2 Confirm that the “Serial0 is up, line protocol is up” message (shown in bold in the
example) appears in the command output.
1700# show interface ser0
Serial0 is up, line protocol is up
Hardware is PowerQUICC Serial
5Configure this interface for PPP encapsulation. 1700(config-if)# encapsulation PPP
6Enable this interface and the configuration changes you have just
made on the interface. 1700(config-if)# no shutdown
7Exit configuration mode for this interface. 1700(config-if)# exit
Step Task Router Prompt Command
1Enable RIP routing on the router and enter router
configuration mode. 1700(config)# router rip
2Specify the router to use RIP version 2. 1700(config-router)# version 2
3Enable Enhanced IGRP for this network. 1700(config-router)# network 10.0.0.0
4Disable automatic summarization of subnet routes into
network-level routes. 1700(config-router)# no auto-summary
5Configure the router to forward packets addressed to a subnet
of a network with no network default route. 1700(config-router)# ip classless
6Exit router configuration mode. 1700(config-router)# exit
Step Task Router Prompt Command
1Specify the console terminal line and enter line configuration mode. 1700(config)# line console 0
2Set the interval that the EXEC command interpreter waits until user input
is detected. 1700(config-line)# exec-timeout 5
3Specify a virtual terminal for remote console access 1700(config-line)# line vty 0 4
4Specify a password on the line. 1700(config-line)# password <lineaccess>
5Enable password checking at terminal session login. 1700(config-line)# login
6Exit configuration mode. 1700(config-line)# end
Step Task Router Prompt Command

Configuring a Leased Line 4-5
Troubleshooting Leased Line Problems
Description: leased line to headquarters
Interface is unnumbered. Using address of FastEthernet0 (10.1.1.1)
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation PPP, loopback not set, keepalive set (10 sec)
LCP Closed
.
.
.
Step 3 If you see the message shown in the example command output, continue configuration by
re-entering global configuration mode.
If you see one of the following messages instead of the one shown in the example
command output, refer to the “Troubleshooting Leased Line Problems” section for
possible causes of the message and suggested actions:
•Serial x is down, line protocol is down.
•Serial x is up, line protocol is down.
•Serial x is up, line protocol is up (looped).
•Serial x is administratively down, line protocol is up.
Troubleshooting Leased Line Problems
Table 4-1 describes some common leased line problems, possible causes, and suggested actions that
you can take to solve the problem.
Table 4-1 Leased Line Problems and Suggested Actions
Line State Possible Cause Suggested Actions
Serial x is down,
line protocol is down. The router is not sensing a carrier detect (CD) signal due to one of the following reasons:
• Telephone company problem, such as the line is down
or not connected to the DSU/CSU.
• Faulty or incorrect cabling of the router.
• Local DSU/CSU hardware failure.
• Local router hardware failure.
Following are some steps you can take to isolate the
problem:
• Check the LEDs on the external DSU/CSU for CD
activity.
• Refer to the Cisco 1700 Router Hardware Installation
Guide to confirm that your router is correctly installed
using the correct cables.
• Contact the telephone company.
• Connect the leased line to another port, if possible. If
the connection come up, there is a hardware failure.
Contact your Cisco reseller.
Serial x is up,
line protocol is down. Possible causes for this line state are
• Local or remote router misconfigured.
• The remote router is not sending keepalive packets.
• Problem with the leased line.
• The serial clock transmit external is not set on the
DSU/CSU.
• Local or remote DSU/CSU hardware failure.
• Router hardware failure.
Following are some steps you can take to isolate the
problem:
• Perform DSU/CSU loopback tests. During local
loopback, enter the show interface ser0 command. If
the line protocol is shown as up, there might be a
problem with the telephone company, or the remote
router is down.
• Refer to the Cisco 1700 Router Hardware Installation
Guide to confirm that your router is correctly installed
using the correct cables.
• Connect the leased line to another port, if possible. If
the connection come up, there is a hardware failure.
Contact your Cisco reseller.

Troubleshooting Leased Line Problems
Cisco 1700 Router Software Configuration Guide
4-6
Serial x is up,
line protocol is up
(looped).
The possible cause is that a loop exists in the circuit.
The sequence number in the keepalive packet changes to
a random number when a loop is first detected. If the
same random number is returned over the line, a loop
exists.
Following are some steps you can take to isolate the
problem:
• Use the write terminal privileged EXEC command
to display any instances of the loopback command. If
the router has been configured with the loopback
command, enter the no loopback command to remove
the loop.
• Check to see if the DSU/CSU is configured in manual
loopback mode. If it is, disable manual loopback.
• Reset the DSU/CSU.
• If you are unable to isolate the problem, contact the
telephone company for help with troubleshooting.
Serial x is
administratively down,
line protocol is up.
The possible causes for this state are
• The serial interface has been disabled with the
shutdown interface configuration command.
• Different interfaces on the router are using the same
IP address.
Following are some steps you can take to isolate the
problem:
• Use the show configuration privileged EXEC
command to display the serial port configuration. If
“shutdown” is displayed after “interface Serial0,” use
the no shutdown interface configuration command to
enable the interface.
• Use the show interface privileged EXEC command
to display the IP addresses for all router interfaces.
Use the ip address interface configuration command
to assign unique IP addresses to the router interfaces.
Table 4-1 Leased Line Problems and Suggested Actions
Line State Possible Cause Suggested Actions