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Cisco 800 Series Routers

Configuring a Cisco 827 Router With IRB and NAT Using RFC1483 Bridging

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Document ID: 12901

Updated: Jun 01, 2005

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Introduction

This sample configuration shows a Cisco 827 Digital Subscriber Line (DSL) router that is connected to a Cisco 6130 Digital Subscriber Line Access Multiplexer (DSLAM), that terminates on a Cisco 6400 Universal Access Concentrator (UAC).

The Cisco 827, configured with RFC1483 Bridging and integrated routing and bridging (IRB), runs network address translation (NAT).

The Cisco 6400 asynchronous transfer mode (ATM) interface is configured with routed bridge encapsulation (RBE).

For the Cisco 6400, the ATM RBE feature on the Cisco 6400 node route processor (NRP) routes IP over bridged RFC1483 Ethernet traffic from a stub-bridged LAN.

Bridged IP packets received on an ATM interface configured in route-bridged mode are routed via the IP header. The interfaces take advantage of the characteristics of a stub LAN topology commonly used for DSL access and offer increased performance and flexibility over IRB.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on these software and hardware versions:

  • Cisco 827-4V Customer Premises Equipment (CPE) IOS® Software Release 12.1(1)XB

  • Cisco 6400 UAC-NRP IOS Software Release 12.0(7)DC

  • Cisco 6400 UAC-Node Switch Processor (NSP) IOS Software Release 12.0(4)DB

  • Cisco 6130 DSLAM-NI2 IOS Software Release 12.1(1)DA

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

Configure

In this section, you are presented with the information you can use to configure the features described in this document.

Note: In order to find additional information on the commands used in this document, use the Command Lookup Tool (registered customers only) .

Network Diagram

This document uses the network setup shown in this diagram.

827rfc_irb_nat.gif

Configurations

This document uses these configurations.

Cisco 827 
Current configuration: 
! 
version 12.1 
service timestamps debug datetime msec 
service timestamps log datetime msec 
! 
hostname R1
!
ip subnet-zero 
!
bridge irb 
! 
interface Ethernet0 
 ip address 10.0.0.1 255.0.0.0 
 no ip directed-broadcast 
 ip nat inside 
 no ip mroute-cache 
! 
interface ATM0 
 no ip address 
 no ip directed-broadcast 
 no ip mroute-cache 
 no atm ilmi-keepalive 
 pvc 4/100 
  encapsulation aal5snap 
 ! 
 bundle-enable 
 bridge-group 1 
 hold-queue 224 in 
! 
interface BVI1 
 ip address 172.16.0.1 255.255.0.0 
 no ip directed-broadcast 
 ip Nat outside 
! 
ip Nat inside source list 1 interface BVI1 overload 
ip classless 
ip route 0.0.0.0 0.0.0.0 <next hop IP address>

!--- The next hop IP address is also called the 
!--- default gateway and is provided by your ISP. 
!--- For this example, one valid default gateway 
!--- can be the loopback interface of the 
!--- Cisco 6400 NRP, 172.16.0.2.

no ip http server 
! 
access-list 1 permit 10.0.0.0 0.255.255.255 
bridge 1 protocol ieee 
 bridge 1 route ip 
! 
voice-port 1 
 timing hookflash-in 0 
! 
voice-port 2 
 timing hookflash-in 0 
! 
voice-port 3 
 timing hookflash-in 0 
! 
voice-port 4 
 timing hookflash-in 0 
!
end

Cisco 6400 NRP - Example 1 
Current configuration: 
! 
version 12.0 
no service pad 
service timestamps debug datetime msec 
service timestamps log datetime msec 
! 
hostname NRP 

! 
redundancy 
 main-cpu 
 no auto-sync standard 
 no secondary console enable 
ip subnet-zero 
! 
interface Loopback1 
 ip address 172.16.0.2 255.255.0.0 
 no ip directed-broadcast 
! 
interface ATM0/0/0 
 no ip address 
 no ip directed-broadcast 
 no ip mroute-cache 
 no ATM ilmi-keepalive 
! 
interface ATM0/0/0.4 point-to-point

!--- The interface ATM0/0/0.4 point-to-point uses ip
!--- unnumbered Loopback1 for the IP address requirements.

 ip unnumbered Loopback1 
 no ip directed-broadcast 
 no ip route-cache 
 ATM route-bridged ip 
 PVC 4/100 
  encapsulation aal5snap 
 ! 
interface Ethernet0/0/1 
 no ip address 
 no ip directed-broadcast 
! 
interface Ethernet0/0/0 
 no ip directed-broadcast 
! 
interface FastEthernet0/0/0 
 no ip address 
 no ip directed-broadcast 
 full-duplex 
! 
ip classless 
ip route 172.16.0.1 255.255.255.255 ATM0/0/0.4 
end

Cisco 6400 NRP - Example 2 
Current configuration: 
! 
version 12.0 
no service pad 
service timestamps debug datetime msec 
service timestamps log datetime msec 
! 
hostname NRP 

! 
redundancy 
 main-CPU 
 no auto-sync standard 
 no secondary console enable 
ip subnet-zero 
! 
interface ATM0/0/0 
 no ip address 
 no ip directed-broadcast 
 no ip mroute-cache 
 no ATM ilmi-keepalive 
! 
interface ATM0/0/0.4 point-to-point 
 ip address 172.16.0.2 255.255.0.0 
 no ip directed-broadcast 
 no ip route-cache 
 ATM route-bridged ip 
 PVC 4/100 
  encapsulation aal5snap 
 ! 
interface Ethernet0/0/1 
 no ip address 
 no ip directed-broadcast 
! 
interface Ethernet0/0/0 
 no ip directed-broadcast 
! 
interface FastEthernet0/0/0 
 no ip address 
 no ip directed-broadcast 
 full-duplex 
! 
ip classless 
ip route 172.16.0.1 255.255.255.255 ATM0/0/0.4
end

Verify

There is currently no verification procedure available for this configuration.

Troubleshoot

There is currently no specific troubleshooting information available for this configuration.

Related Information

Updated: Jun 01, 2005
Document ID: 12901