Cisco DSL Router Configuration and Troubleshooting Guide - Step-by-Step Configuration of IRB with a Dynamic IP Address

Introduction

Your Internet Service Provider (ISP) has assigned a dynamic public IP address to your Cisco Digital Subscriber Line (DSL) router.

Note: This example highlights two types of configurations:

• Dynamic Host Configuration Protocol (DHCP) Server

• Network Address Translation (NAT).

Important: Before you begin, close all programs on the PC that might be monitoring your COM port. Devices such as PDAs and digital cameras often place programs in the system tray that render your COM port unusable for the configuration of your Cisco DSL Router.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Configuration Procedures

Connect the Cisco DSL Router and Your PC

A console connection is made with a rolled cable and connects the console port of the Cisco DSL Router to a COM port on a PC. The console cable that is included with the Cisco DSL Router is a flat light blue cable. For more information on the pinouts of a rolled cable, or the pinouts of an RJ-45 to DB9 converter, refer to Cabling Guide for Console and AUX Ports.

1. Connect the RJ-45 connector on one end of a Cisco console cable to the console port of the Cisco DSL Router.

2. Connect the RJ-45 connector at the other end of the console cable to an RJ-45 to DB9 converter.

3. Connect the DB9 connector to an open COM port on your PC.

Start and Set Up HyperTerminal

Complete these steps:

1. Start the HyperTerminal program on the PC.

2. Set up your HyperTerminal session.

   1. Assign a name to your session and click OK.

   2. In the Connect To window, click Cancel.

   3. Choose File > Properties.

   4. From the Properties window, go to the Connect Using list and select the COM port where you connect the DB9 end of the console cable.

   5. From the Properties window click Configure and fill in these values:

      • Bits per second: 9600

      • Data bits: 8

      • Parity: None

      • Stop bits: 1

      • Flow Control: None

   6. Click OK.

   7. From the Call menu, click Disconnect.

   8. From the Call menu, click Call.

   9. Press Enter until you see a router prompt on your HyperTerminal window.

Clear Existing Configurations on the Cisco DSL Router

Complete these steps:

1. Type enable at the router prompt in order to enter privileged mode.

   Router>enable
   Router#
   
   !--- The # symbol indicates that you are in privileged mode.
   
   

2. Clear existing configurations on the router.

   Router#write erase
   

3. Reload the router so that it boots with a blank startup configuration.

   Router#reload
   System configuration has been modified. Save? [yes/no]:no
   Proceed with reload? [confirm]yes
   
   !--- The router reload can take a few minutes.
   
   

4. After the router has reloaded, enter enable mode again.

   Router>enable
   Router#

Configure the Cisco DSL Router

Complete these steps:

1. Configure service timestamp to properly log and display debug output in the troubleshooting section.

   Router#configure terminal
   Router(config)#service timestamps debug datetime msec
   Router(config)#service timestamps log datetime msec
   Router(config)#end
   

2. Disable logging console on your Cisco DSL Router to suppress console messages that might be triggered while you configure the router.

   Router#configure terminal
   Router(config)#no logging console
   Router(config)#end
   

3. Configure ip routing, ip subnet-zero, and ip classless to provide flexibility in routing configuration options.

   Router#configure terminal
   Router(config)#ip routing
   Router(config)#ip subnet-zero
   Router(config)#ip classless
   Router(config)#end
   

4. Configure integrated routing and bridging (IRB) global parameters.

   Router#configure terminal
   Router(config)#bridge irb
   Router(config)#bridge 1 protocol ieee
   Router(config)#bridge 1 route ip
   Router(config)#end
   

5. Configure an IP address and subnet mask on the Cisco DSL Router Ethernet interface.

   For NAT: (Optional) Enable NAT inside on the Ethernet interface.

   Router#configure terminal
   Router(config)#interface ethernet 0
   Router(config-if)#ip address <ip address> <subnet mask>
   
    !--- For NAT: 
   
   Router(config-if)#ip nat inside
   
   Router(config-if)#no shut
   Router(config-if)#end
   

6. Configure the ATM interface of your Cisco DSL Router with an ATM permanent virtual circuit (PVC), encapsulation type, and bridge group.

   Router#configure terminal
   Router(config)#interface atm 0
   Router(config-if)#bridge-group 1
   Router(config-if)#pvc <vpi/vci>
   Router(config-if-atm-vc)#encapsulation aal5snap
   Router(config-if-atm-vc)#no shut
   Router(config-if-atm-vc)#end
   

7. Create and configure a bridged virtual interface (BVI) in order to enable a dynamic IP address to be assigned to your Cisco DSL Router.

   For NAT: (Optional) Enable NAT outside on the BVI interface.

   Router#configure terminal
   Router(config)#interface bvi 1
   Router(config-if)#mac address <address from line 2 of show interface bvi1>
   
   Router(config-if)#ip address dhcp client-id ethernet0
   Router(config-if)#no ip directed-broadcast
    
    !--- For NAT: 
   
   Router(config-if)#ip nat outside
   
   Router(config-if)#end
   

8. Configure a default route using the ISP default gateway as the next hop.

   Router#configure terminal
   Router(config)#ip route 0.0.0.0 0.0.0.0 <default gateway to isp>
   
   Router(config)#end
   

9. This step is for NAT—Configure global NAT commands on the Cisco DSL Router in order to allow sharing of the static public IP address of the Dialer interface.

   Router#configure terminal
   Router(config)#ip nat inside source list 1 interface bvi1 overload
   Router(config)#access-list 1 permit <ip network address of ethernet0> 
   
    
   <wildcard mask>
   
   Router(config)#end
   

   Optional Configurations

   NAT Pool, if additional IP addresses have been provided by your ISP.

   Router(config)#ip nat inside source list 1 interface bvi1 overload 
   Router(config)#ip nat pool <nat pool name> <first ip address> <last ip address> netmask <subnet mask>
   
   Router(config)#end
   

   Static NAT, if Internet users require access to internal servers.

   Router(config)#ip nat inside source static tcp <inside ip address of server> 
    {80 or 25} <outside well-known ip address of server> {80 or 25} extendable
   Router(config)#end
   

10. This step is for the DHCP Server—(Optional) Configure the Cisco DSL Router as a DHCP server with a pool of IP addresses to assign to hosts connected to the Ethernet interface of the Cisco DSL Router. The DHCP server dynamically assigns an IP address, Domain Name Server (DNS), and the default gateway IP address to your hosts.

    Router#configure terminal
    Router(config)#ip dhcp excluded-address <ip address of ethernet0>
    
    Router(config)#ip dhcp pool <dhcp pool name>
    
    Router(dhcp-config)#network <ip network address of ethernet0> <subnet mask>
      
    Router(dhcp-config)#default-router <ip address of ethernet0> 
    
    Router(dhcp-config)#dns-server <ip address of primary dns server> <ip address of secondary dns server>
    
    Router(dhcp-config)#end
    

11. Enable logging console on the Cisco DSL Router, and write all the changes to memory.

    Router#configure terminal
    Router(config)#logging console
    Router(config)#end
    *Jan 1 00:00:00.100: %SYS-5-CONFIG_I: Configured from console by console
    Router#write memory
    Building configuration... [OK]
    Router#

Configuration

This is the configuration that is built after you have completed the procedures in the Configuration Procedures section of this document.

!--- Comments contain explanations and additional information.


service timestamps debug datetime msec
service timestamps log datetime msec
!
bridge irb
!
ip subnet-zero
!

!--- For the DHCP Server: 

ip dhcp excluded-address <ip address of ethernet0>
ip dhcp pool <dhcp pool name>
 network <ip network address of ethernet0> <subnet mask>
 default-router <ip address of ethernet0>
 dns-server <ip address of dns server>
!
interface ethernet0
 no shut
 ip address <ip address> <subnet mask>

!--- For NAT: 

 ip nat inside
 no ip directed-broadcast
!
interface atm0
 no shut
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 pvc <vpi/vci>
  encapsulation aal5snap
 
!--- Common PVC values supported by ISPs are 0/35 or 8/35. !--- Confirm your PVC values with your ISP.

 !
 bridge-group 1
!
interface bvi1
 mac-address <address from line 2 of show interface bvi1>
 ip address dhcp client-id ethernet0

!--- For NAT: 

 ip nat outside
 no ip directed-broadcast
!

!--- For NAT: 

ip nat inside source list 1 interface bvi1 overload

!--- If you have a pool (a range) of public IP addresses provided !--- by your ISP, you can use a NAT Pool. Replace !--- ip nat inside source list 1 interface bvi1 overload 

 

!--- with these two configuration statements: !--- ip nat inside source list 1 pool <nat pool name> overload !--- ip nat pool <nat pool name> <first ip address> <last ip address> !--- netmask <subnet mask>



!--- If Internet users require access to an internal server, you can !--- add these static NAT configuration statements: !--- ip nat inside source static tcp <inside ip address of server> {80 or 25} !--- <outside well-known ip address of server> {80 or 25} extendable !--- Note: TCP port 80 (HTTP/web) and TCP port 25 (SMTP/mail) are used !--- for this example. You can open other TCP or UDP ports, if needed.

! 
ip classless 
ip route 0.0.0.0 0.0.0.0 <default gateway to isp>

!--- For NAT: 

access-list 1 permit <ip network address of ethernet0> <wildcard mask>

!--- In this configuration, access-list 1 defines a standard access list !--- that permits the addresses that NAT translates. For example, if !--- your private IP network is 10.10.10.0, the configuration of !--- access-list 1 permit 10.10.10.0 0.0.0.255 allows NAT to translate !--- packets with source addresses between 10.10.10.0 and 10.10.10.255.

!
bridge 1 protocol ieee
 bridge 1 route ip
!
end   

Verify

Your Cisco DSL Router is now operational for Asymmetric Digital Subscriber Line (ADSL) service. You can issue a show run command in order to see the configuration.

Router#show run
Building configuration...

The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.

Troubleshoot

Refer to Troubleshooting RFC1483 Bridging with IRB if your ADSL service does not work properly.

Return to the previous page of this configuration and troubleshooting guide - IRB with a Dynamic IP Address.

Return to the main page of the Cisco DSL Router Configuration and Troubleshooting Guide.

Related Information

• Technical Support & Documentation - Cisco Systems